Hibernate Tools

Reference Guide

Version: 3.2.0.GA

Table of Contents

Preface ..................................................................................................................................................iv

1. Download and install Hibernate Tools ..................................................................................................1

1.1. JBoss Tools .............................................................................................................................1

1.2. Eclipse IDE .............................................................................................................................1

1.2.1. Usage of Eclipse WTP ...................................................................................................1

1.3. Ant ..........................................................................................................................................2

2. Code generation architecture ................................................................................................................3

2.1. Hibernate Meta Model ..............................................................................................................3

2.2. Exporters .................................................................................................................................4

3. Eclipse Plugins ...................................................................................................................................5

3.1. Introduction .............................................................................................................................5

3.2. Creating a Hibernate configuration file ......................................................................................5

3.3. Creating a Hibernate Console configuration ...............................................................................7

3.4. Reverse engineering and code generation .................................................................................13

3.4.1. Code Generation Launcher ...........................................................................................14

3.4.2. Exporters ....................................................................................................................17

3.5. Hibernate Mapping and Configuration File Editor ....................................................................20

3.5.1. Java property/class completion .....................................................................................20

3.5.2. Table/Column completion ............................................................................................21

3.5.3. Configuration property completion ...............................................................................22

3.6. Reveng.xml editor ..................................................................................................................23

3.7. Hibernate Console perspective ................................................................................................25

3.7.1. Viewing the entity structure .........................................................................................25

3.7.1.1. Mapping Diagram .............................................................................................26

3.7.2. Prototyping Queries .....................................................................................................27

3.7.2.1. Dynamic Query Translator ................................................................................28

3.7.3. Properties view ............................................................................................................28

3.8. Enable debug logging in the plugins ........................................................................................29

4. Ant Tools .........................................................................................................................................30

4.1. Introduction ...........................................................................................................................30

4.2. The <hibernatetool> ant Task ...............................................................................................30

4.2.1. Basic examples ............................................................................................................31

4.3. Hibernate Configurations ........................................................................................................31

4.3.1. Standard Hibernate Configuration (<configuration>) .....................................................32

4.3.1.1. Example ...........................................................................................................32

4.3.2. Annotation based Configuration (<annotationconfiguration>) ........................................33

4.3.3. JPA based configuration (<jpaconfiguration>) ...............................................................33

4.3.4. JDBC Configuration for reverse engineering (<jdbcconfiguration>) ...............................34

4.3.4.1. Example ...........................................................................................................35

4.4. Exporters ...............................................................................................................................35

4.4.1. Database schema exporter (<hbm2ddl>) .......................................................................35

4.4.1.1. Example ...........................................................................................................35

4.4.2. POJO java code exporter (<hbm2java>) .........................................................................36

4.4.2.1. Example ...........................................................................................................36

JBoss Version: 3.2.0.GA

Hibernate Tools

4.4.3. Hibernate Mapping files exporter (<hbm2hbmxml>) .........................................................36

4.4.3.1. Example ...........................................................................................................36

4.4.4. Hibernate Configuration file exporter (<hbm2cfgxml>) ...................................................37

4.4.5. Documentation exporter (<hbm2doc>) ...........................................................................37

4.4.6. Query exporter (<query>) ............................................................................................37

4.4.6.1. Examples .........................................................................................................37

4.4.7. Generic Hibernate metamodel exporter (<hbmtemplate>) ...............................................38

4.4.7.1. Exporter via <hbmtemplate> ..............................................................................38

4.5. Using properties to configure Exporters ...................................................................................39

4.5.1. <property> and <propertyset>...................................................................................39

4.5.2. Getting access to user specific classes ...........................................................................39

4.5.2.1. Example ...........................................................................................................39

5. Controlling reverse engineering .........................................................................................................40

5.1. Default reverse engineering strategy ........................................................................................40

5.2. hibernate.reveng.xml file ........................................................................................................40

5.2.1. Schema Selection (<schema-selection>) .......................................................................41

5.2.1.1. Examples .........................................................................................................42

5.2.2. Type mappings (<type-mapping>) ................................................................................42

5.2.2.1. Example ...........................................................................................................42

5.2.3. Table filters (<table-filter>) ..........................................................................................43

5.2.4. Specific table configuration (<table>) ...........................................................................44

5.2.4.1. <primary-key> .................................................................................................44

5.2.4.2. <column> .........................................................................................................44

5.2.4.3. <foreign-key> ..................................................................................................45

5.3. Custom strategy .....................................................................................................................46

5.4. Custom Database Metadata .....................................................................................................46

6. Controlling POJO code generation .....................................................................................................47

6.1. The <meta> attribute ...............................................................................................................47

6.1.1. Recomendations ..........................................................................................................49

6.1.1.1. Dangers of a class level use-in-string and use-in-equals meta attributes when

having bi-directional associations ..................................................................................49

6.1.1.2. Be aware of putting at class scope level <meta> attribute use-in-equals .............50

6.1.2. Advanced <meta> attribute examples ............................................................................51

6.1.2.1. Generate pre/post-conditions for methods ...........................................................51

JBoss Version: 3.2.0.GA

iii

Preface

Hibernate Tools is a toolset for Hibernate 3 and related projects. The tools provide Ant tasks and Eclipse plugins

for performing reverse engineering, code generation, visualization and interaction with Hibernate.

JBoss Version: 3.2.0.GA

Download and install Hibernate Tools

Hibernate Tools can be used "standalone" via Ant 1.6.x or fully integrated into a Eclipse 3.3.x + WTP 2.x based

IDE, such as JBoss Tools or an default Eclipse 3.3.x + WTP 2.x installation. The following describes the install

steps in these environments.

1.1. JBoss Tools

JBoss Tools 2.x includes Hibernate Tools and thus nothing is required besides downloading and installing JBoss

Tools. If you need to update to a newer version of the Hibernate Tools just follow the instructions in the Eclipse

IDE section.

1.2. Eclipse IDE

To install into any Eclipse 3.3.x based Eclipse IDE you can either download the Hibernate Tools distribution from

the Hibernate website [http://tools.hibernate.org] or use the JBoss Tools update site (see also ht-

tp://tools.hibernate.org for links to the update site).

If you download the Hibernate Tools distribution you need to place the /plugins and /feature directory into your ec-

lipse directory or eclipse extensions directory. Sometimes Eclipse does not automatically detect new plugins and

thus the tools will not be activated. To ensure eclipse sees these changes run eclipse with the -clean option. E.g. ec-

lipse -clean Using the updatesite does not require any additional steps.

Note

If you need more basic instructions on installing plugins and general usage of eclipse then check out ht-

tps://eclipse-tutorial.dev.java.net/

and

especially

ht-

tps://eclipse-tutorial.dev.java.net/visual-tutorials/updatemanager.html which covers using the update man-

ager.

1.2.1. Usage of Eclipse WTP

The Hibernate Tools plugins currently uses WTP 2.x which at this time is the latest stable release from the Eclipse

Webtools project.

Because the WTP project not always have had proper versioning of their plugins there might exist WTP plugins in

your existing eclipse directory from other Eclipse based projects that are from an earlier WTP release but has either

the same version number or higher. It is thus recommended that if you have issues with WTP provided features to

try and install the plugins on a clean install of eclipse to ensure there are no version collisions.

JBoss Version: 3.2.0.GA

1.3. Ant

Download and install Hibernate Tools

To use the tools via Ant you need the hibernate-tools.jar and associated libraries. The libraries are included in the

distribution from the Hibernate website and the Eclipse updatesite. The libraries are located in the eclipse plugins

directory at /plugins/org.hibernate.eclipse.x.x.x/lib/tools/. These libraries are 100% independent from

the eclipse platform. How to use these via ant tasks are described in the Ant chapter.

JBoss Version: 3.2.0.GA

Code generation architecture

The code generation mechanism in the Hibernate Tools consists of a few core concepts. This section explains their

overall structure which are the same for the Ant and Eclipse tools.

2.1. Hibernate Meta Model

The meta model is the model used by Hibernate Core to perform its object relational mapping. The model includes

information about tables, columns, classes, properties, components, values, collections etc. The API is in

org.hibernate.mapping and its main entry point is the Configuration class, the same class that is used to build a

session factory.

The model represented by the Configuration class can be build in many ways. The following list the currently

supported ones in Hibernate Tools.

• A Core configuration uses Hibernate Core and supports reading hbm.xml files, requires a hibernate.cfg.xml .

Named core in Eclipse and <configuration>in ant.

• A Annotation configuration uses Hibernate Annotations and supports hbm.xml and annotated classes, requires a

hibernate.cfg.xml . Named annotations in Eclipse and <annotationconfiguration>in ant.

• A JPA configuration uses a Hibernate EntityManager and supports hbm.xml and annotated classes requires that

the project has a META-INF/persistence.xml in its classpath. Named JPA in Eclipse and <jpaconfiguration>in

ant.

• A JDBC configuration uses Hibernate Tools reverse engineering and reads its mappings via JDBC metadata +

additional reverse engineering files (reveng.xml). Automatically used in Eclipse when doing reverse engineering

from JDBC and named <jdbcconfiguration>in ant.

In most projects you will normally use only one of the Core, Annotation or JPA configuration and possibly the JD-

BC configuration if you are using the reverse engineering facilities of Hibernate Tools. The important thing to note

is that no matter which Hibnerate Configuration type you are using Hibernate Tools supports them.

The following drawing illustrates the core concepts:

JBoss Version: 3.2.0.GA

Figure 2.1. Hibernate Core Concepts

Code generation architecture

The code generation is done based on the Configuration model no matter which type of configuration have been

used to create the meta model, and thus the code generation is independent on the source of the meta model and

represented via Exporters.

2.2. Exporters

Code generation is done in so called Exporters. An Exporter is handed a Hibernate Meta Model represented as a

Configuration instance and it is then the job of the exporter to generate a set of code artifacts.

The tools provides a default set of Exporter's which can be used in both Ant and the Eclipse UI. Documentation for

these Exporters is in the Ant and Eclipse sections.

Users can provide their own customer Exporter's, either by custom classes implementing the Exporter interface or

simply be providing custom templates. This is documented at Section 4.4.7

JBoss Version: 3.2.0.GA

3.1. Introduction

The following features are available in the Hibernate Tools Eclipse plugins:

Eclipse Plugins

Mapping Editor: An editor for Hibernate XML mapping files, supporting auto-completion and syntax highlight-

ing. It also supports semantic auto-completion for class names and property/field names, making it much more ver-

satile than a normal XML editor.

Hibernate Console: The console is a new perspective in Eclipse. It provides an overview of your Hibernate Con-

sole configurations, were you also can get an interactive view of your persistent classes and their relationships. The

console allows you to execute HQL queries against your database and browse the result directly in Eclipse.

Configuration Wizards and Code generation: A set of wizards are provided with the Hibernate Eclipse tools;

you can use a wizard to quickly generate common Hibernate configuration (cfg.xml) files, and from these you can

code generate a series of various artifacts, there is even support for completely reverse engineer an existing data-

base schema and use the code generation to generate POJO source files and Hibernate mapping files.

Eclipse JDT integration: Hibernate Tools integrates into the Java code completion and build support of Java in

Eclipse. This gives you codecompletion of HQL inside Java code plus Hibernate Tools will add problem markers if

your queries are not valid against the console configuration associated with the project.

Please note that these tools do not try to hide any functionality of Hibernate. The tools make working with Hibern-

ate easier, but you are still encouraged/required to read the documentation for Hibernate to fully utilize Hibernate

Tools and especially Hibernate it self.

3.2. Creating a Hibernate configuration file

To be able to reverse engineer, prototype queries, and of course to simply use Hibernate Core a hibern-

ate.properties or hibernate.cfg.xml file is needed. The Hibernate Tools provide a wizard for generating the hibern-

ate.cfg.xml file if you do not already have such file.

Start the wizard by clicking New Wizard (Ctrl+N), select the Hibernate/Hibernate Configuration file (cfg.xml) wiz-

ard and press Next . After selecting the wanted location for the hibernate.cfg.xml file, you will see the following

page:

JBoss Version: 3.2.0.GA

Eclipse Plugins

Figure 3.1. Hibernate Configuration File Wizard

Note

The contents in the combo boxes for the JDBC driver class and JDBC URL change automatically, depend-

ing on the Dialect and actual driver you have chosen.

JBoss Version: 3.2.0.GA

Eclipse Plugins

Enter your configuration information in this dialog. Details about the configuration options can be found in Hibern-

ate reference documentation.

Press Finish to create the configuration file, after optionally creating a Console onfiguration, the hibernate.cfg.xml

will be automatically opened in an editor. The last option Create Console Configuration is enabled by default and

when enabled i will automatically use the hibernate.cfg.xml for the basis of a Console Configuration.

3.3. Creating a Hibernate Console configuration

A Console Configuration describes to the Hibernate plugin how it should configure Hibernate and what configura-

tion files, including which classpath is needed to load the POJO's, JDBC drivers etc. It is required to make usage of

query prototyping, reverse engineering and code generation. You can have multiple named console configurations.

Normally you would just need one per project, but more is definitly possible.

You create a console configuration by running the Console Configuration wizard, shown in the following screen-

shot. The same wizard will also be used if you are coming from the hibernate.cfg.xml wizard and had enabled Cre-

ate Console Configuration .

Note

The wizard will look at the current selection in the IDE and try and auto-detect the settings which you then

can just approve or modify to suit your needs.

JBoss Version: 3.2.0.GA

Eclipse Plugins

Figure 3.2. Creating Hibernate Console Configuration

The dialog consists of three tabs, General for the basic/required settings, Classpath for classpath and Mappings for

additional mappings. The two latter ones is normally not required if you specify a project and it has /hi-

bernate.cfg.xml or /META-INF/persistence.xmlin its project classpath.

The following table describes the available settings. The wizard can automatically detect default values for most of

these if you started the Wizard with the relevant java project or resource selected

Table 3.1. Hibernate Console Configuration Parameters

JBoss Version: 3.2.0.GA

Parameter

Name

Project

Type

Eclipse Plugins

Description

The unique name of the console configuration

The name of a java project which classpath should be used in the

console configuration

Choose between "Core", "Annotations" and "JPA". Note that the

two latter requires running Eclipse IDE with a JDK 5 runtime,

otherwise you will get classloading and/or version errors.

Auto detected

value

Name of the selec-

ted project

Name of the selec-

ted project

No default value

Property file

Path to a hibernate.properties file

First

hibern-

Configuration file Path to a hibernate.cfg.xml file

ate.properties file

found in the selec-

ted project

First hibern-

ate.cfg.xml file

found in the selec-

ted project

Persistence unit

Naming strategy

Entity resolver

Name of the persistence unit to use

Fully qualified classname of a custom NamingStrategy. Only re-

quired if you use a special naming strategy.

Fully qualified classname of a custom EntityResolver. Only re-

quired if you have special xml entity includes in your mapping

files.

No default value

(lets Hibernate En-

tity Manager find

the persistence unit)

No default value

JBoss Version: 3.2.0.GA

Eclipse Plugins

Figure 3.3. Specifying Classpath in Hibernate Console Configuration

Table 3.2. Hibernate Console Configuration Classpath

Parameter Description

Auto detected

value

Classpath

The classpath for loading POJO and JDBC drivers; only needed

if the default classpath of the Project does not contain the re-

empty

JBoss Version: 3.2.0.GA

Parameter

Eclipse Plugins

Description

quired classes. Do not add Hibernate core libraries or dependen-

cies, they are already included. If you get ClassNotFound errors

then check this list for possible missing or redundant directories/

jars.

Auto detected

value

Include

classpath

project

default

from

When enabled the project classpath will be appended to the

classpath specified above.

Enabled

JBoss Version: 3.2.0.GA

Eclipse Plugins

Figure 3.4. Specifying additional Mappings in Hibernate Console Configuration

Table 3.3. Hibernate Console Configuration Mappings

Parameter Description

Auto detected

value

Mapping files

List of additional mapping files that should be loaded. Note: A

hibernate.cfg.xml or persistence.xml can also contain mappings.

Thus if these are duplicated here, you will get "Duplicate map-

empty

JBoss Version: 3.2.0.GA

Parameter

Eclipse Plugins

Description

ping" errors when using the console configuration.

Auto detected

value

Clicking Finish creates the configuration and shows it in the Hibernate Configurations view

Figure 3.5. Console Overview

3.4. Reverse engineering and code generation

A "click-and-generate" reverse engineering and code generation facility is available. This facility allows you to

generate a range of artifacts based on database or an already existing Hibernate configuration, be that mapping files

or annotated classes. Some of these are POJO Java source file, Hibernate *.hbm.xml, hibernate.cfg.xml generation

and schema documentation.

To start working with this process, start the Hibernate Code Generation which is available in the toolbar via the Hi-

bernate icon or via the Run > Hibernate Code Generation menu item.

JBoss Version: 3.2.0.GA

3.4.1. Code Generation Launcher

Eclipse Plugins

When you click on Hibernate Code Generation... the standard Eclipse launcher dialog will appear. In this dialog

you can create, edit and delete named Hibernate code generation "launchers".

Figure 3.6. Getting Hibernate Code Generation Wizard

JBoss Version: 3.2.0.GA

Eclipse Plugins

Figure 3.7. Hibernate Code Generation Wizard

The first time you create a code generation launcher you should give it a meaningfull name, otherwise the default

prefix New_Generation will be used.

Note

The "At least one exporter option must be selected" is just a warning stating that for this launch to work

you need to select an exporter on the Exporter tab. When an exporter has been selected the warning will

disappear.

The dialog also have the standard tabs Refresh and Common that can be used to configure which directories should

be automatically refreshed and various general settings launchers, such as saving them in a project for sharing the

launcher within a team.

JBoss Version: 3.2.0.GA

On the Main tab you see the following fields:

Table 3.4. Code generation "Main" tab fields

Field

Eclipse Plugins

Description

Console Configuration

Output directory

Reverse engineer from

JDBC Connection

Package

reveng.xml

reveng. strategy

Generate basic typed

composite ids

Detect optimistic lock

columns

The name of the console configuration which should be used when code generat-

ing.

Path to a directory into where all output will be written by default. Be aware that

existing files will be overwritten, so be sure to specify the correct directory.

If enabled the tools will reverse engineer the database available via the connec-

tion information in the selected Hibernate Console Configuration and generate

code based on the database schema. If not enabled the code generation will just

be based on the mappings already specified in the Hibernate Console configura-

tion.

The package name here is used as the default package name for any entities found

when reverse engineering.

Path to a reveng.xml file. A reveng.xml file allows you to control certain aspects

of the reverse engineering. e.g. how jdbc types are mapped to hibernate types and

especially important which tables are included/excluded from the process. Click-

ing "setup" allows you to select an existing reveng.xml file or create a new one.

See more details about the reveng.xml file in Chapter 5.

If reveng.xml does not provide enough customization you can provide your own

implementation of an ReverseEngineeringStrategy. The class need to be in the

claspath of the Console Configuration, otherwise you will get class not found ex-

ceptions. See Section 5.3 for details and an example of a custom strategy.

A table that has a multi-colum primary key a <composite-id> mapping will al-

ways be created. If this option is enabled and there are matching foreign-keys

each key column is still considered a 'basic' scalar (string, long, etc.) instead of a

reference to an entity. If you disable this option a <key-many-to-one> instead.

Note: a <many-to-one> property is still created, but is simply marked as non-

updatable and non-insertable.

Automatically detect optimistic lock columns. Controllable via reveng. strategy;

the current default is to use columns named VERSION or TIMESTAMP.

Detect

tables

many-to-many

Automatically detect many-to-many tables. Controllable via reveng. strategy.

Use custom templates

JBoss Version: 3.2.0.GA

If enabled, the Template directory will be searched first when looking up the tem-

Field

Template directory

3.4.2. Exporters

Eclipse Plugins

Description

plates, allowing you to redefine how the individual templates process the hibern-

ate mapping model.

A path to a directory with custom templates.

The Exporters tab is used to specify which type of code that should be generated. Each selection represents an Ex-

porter that are responsible for generating the code, hence the name.

JBoss Version: 3.2.0.GA

Figure 3.8. Selecting Exporters

Eclipse Plugins

The following table describes in short the various exporters. Remember you can add/remove any Exporters depend-

ing on your needs.

Table 3.5. Code generation "Exporter" tab fields

JBoss Version: 3.2.0.GA

Field

Domain code

DAO code

Hibernate XML Map-

pings

Hibernate XML Config-

uration

Schema Documentation

(.html)

Eclipse Plugins

Description

Generates POJO's for all the persistent classes and components found in the given

Hibernate configuration.

Generates a set of DAO's for each entity found.

Generate mapping (hbm.xml) files for each entity

Generate a hibernate.cfg.xml file. Used to keep the hibernate.cfg.xml uptodate

with any new found mapping files.

Generates set of html pages that documents the database schema and some of the

mappings.

Generic

(hbmtemplate)

Exporter

Fully customizable exporter which can be used to perform custom generation.

Each Exporter listens to certain properties and these can be setup in the Properties section where you can add/

remove predefined or customer properties for each of the exporters. The following table lists the time of writing

pre-defined properties:

Table 3.6. Exporter Properties

jdk5

ejb3

Name

Generate Java 5 syntax

Generate EJB 3 annotations

Description

for_each

template_path

template_name

outputdir

JBoss Version: 3.2.0.GA

Specifies which type of model elements the exporter should create a file and run

through the templates. Possible values are: entity, component, configuration

Custom template directory for this specific exporter. You can use Eclipse vari-

ables.

Name for template relative to the template path

Custom output directory for this specific exporter. You can use Eclipse variables.

Name

file_pattern

dot.executable

Eclipse Plugins

Description

Pattern to use for the generated files, relatively for the output dir. Example:

{package-name}/{class-name}.java

executable to run GraphViz (only relevant, but optional for Schema documenta-

tion)

3.5. Hibernate Mapping and Configuration File Editor

The Hibernate Mapping file editor provides XML editing functionality for the hbm.xml and cfg.xml files. The editor

is based on the Eclipse WTP tools and extend its functionallity to provide Hibernate specific code completion.

Figure 3.9. XML Editing Functionality

3.5.1. Java property/class completion

Package, class, and field completion is enabled for relevant XML attributes. The auto-completion detects its con-

text and limits the completion for e.g. <property> and only shows the properties/fields available in the enclosing

JBoss Version: 3.2.0.GA

Eclipse Plugins

<class> , <subclass> etc. It is also possible to navigate from the hbm.xml files to the relevant class/field in java

code.

Figure 3.10. Navigation Functionallity

This is done via the standard hyperlink navigation functionallity in Eclipse; per default it is done by pressing F3

while the cursor is on a class/field or by pressing Ctrl and the mouse button to perform the same navigation.

For java completion and navigation to work the file needs to reside inside an Eclipse Java project, otherwise no

completion will occur.

Note

Java completion does not require a Hibernate console configuration to be used.

3.5.2. Table/Column completion

Table and column completion is also available for all table and column attributes.

JBoss Version: 3.2.0.GA

Figure 3.11. Table and Column Completion

Eclipse Plugins

Note that it requires a proper configured hibernate console configuration and this configuration should be the de-

fault for the project where the hbm.xml resides.

You can check which console configuration is selected under the Properties of a project and look under the Hibern-

ate Settings page. When a proper configuration is selected it will be used to fetch the table/column names in the

background.

Note

Currently it is not recommended to use this feature on large databases since it does not fetch the informa-

tion iteratively. It will be improved in future versions.

3.5.3. Configuration property completion

In cfg.xml code completion for the value of <property> name attributes is available.

Figure 3.12. Property Completion

JBoss Version: 3.2.0.GA

3.6. Reveng.xml editor

Eclipse Plugins

A reveng.xml file is used to customize and control how reverse engineering is performed by the tools. The plugins

provide and editor to ease the editing of this file and hence used to configure the reverse engineering process.

The editor is intended to allow easy definition of type mappings, table include/excludes and specific override set-

tings for columns, e.g. define a explicit name for a column when the default naming rules is not applicable.

Note that not all the features of the .reveng.xml file is exposed or fully implemented in the editor, but the main

functionallity is there. To understand the full flexibility of the reveng.xml, please see Section 5.2

The editor is activated as soon as an .reveng.xml file is opened. To get an initial reveng.xml file the reveng.xml wiz-

ard can be started via Ctrl+N or via the code generation launcher.

The following screentshot shows the Overview page where the wanted console configuration is selected

(auto-detected if Hibernate 3 support is enabled for the project)

Figure 3.13. Overview Page

The Table Filter page allows you to specify which tables to include and exclude. Pressing refresh shows the tables

from the database that have not yet been excluded.

JBoss Version: 3.2.0.GA

Figure 3.14. Table Filters Page

Eclipse Plugins

The Type Mappings page is used for specifying type mappings from jdbc types to any Hibernate type (including

usertypes) if the default rules are not applicable.

JBoss Version: 3.2.0.GA

Figure 3.15. Type Mappings Page

Eclipse Plugins

The Table and Columns page allow the user to explicit set e.g. which hibernatetype and propertyname that should

be used in the reverse engineered model.

Figure 3.16. Table and Columns Page

3.7. Hibernate Console perspective

The Hibernate Console perspective combines a set of views which allow you to see the structure of your mapped

entities/classes, edit HQL queries, execute the queries, and see the results. To use this perspective you need to cre-

ate a console configuration.

3.7.1. Viewing the entity structure

To view your new configuration and entity/class structure, expand the Hibernate Console configuration by clicking

on the + icon.

Clicking on the small + symbol allows you to browse the class/entity structure and see the relationships.

JBoss Version: 3.2.0.GA

Figure 3.17. Hibernate Console Perspective

Eclipse Plugins

Hibernate Console perspective showing entity structure, query editor and result

The console configuration does not dynamically adjust to changes done in mappings and java code; to reload the

configuration select the configuration and click the Reload button in the view toolbar or in the context menu.

3.7.1.1. Mapping Diagram

A mapping diagram for entities are available by right clicking on the entity you want an mapping diagram for and

then choose Open Mapping Diagram

JBoss Version: 3.2.0.GA

Figure 3.18. Mapping Diagram

3.7.2. Prototyping Queries

Eclipse Plugins

Queries can be prototyped by entering them in the HQL or Criteria editor. The query editors are opened by right-

clicking the Console configuration and selecting either HQL Editor or Criteria Editor.

If the menu item is disabled then you need to first create an SessionFactory. That is done by simply expanding the

Session Factory node.

Executing the query is done by clicking the green run button in the toolbar or pressing Ctrl+Enter.

Errors during creation of the SessionFactory or running the queries (e.g. if your configuration or query is incor-

rect) will be shown in a message dialog or inlined in the view that detected the error, you may get more information

about the error in the Error Log view on the right pane.

JBoss Version: 3.2.0.GA

Eclipse Plugins

Results of a query will be shown in the Query result view and details of possible errors (syntax errors, database er-

rors, etc.) can be seen in the Error Log view.

Note

HQL queries are executed by default using list() thus without any limit of the size of the output the query

could return a large result set. You might run out of memory. To avoid this you can put a value in the Max

results field to reduce the number of elements returned.

3.7.2.1. Dynamic Query Translator

If the Hibernate Dynamic Query Translator view is visible while writing in the HQL editor it will show the gener-

ated SQL for a HQL query.

Figure 3.19. Hibernate Dynamic Query Translator View

The translation is done each time you stop typing into the editor, if there are an error in the HQL the parse excep-

tion will be shown embedded in the view.

3.7.3. Properties view

The Properties view shows the structure of any selected persistent object in the results view. Editing is not yet sup-

ported.

JBoss Version: 3.2.0.GA

Figure 3.20. Properties View

Eclipse Plugins

3.8. Enable debug logging in the plugins

It is possible to configure the eclipse plugin to route all logging made by the plugins and hibernate code it self to

the Error log view in Eclipse.

This is done by editing the hibernate-log4j.properties in org.hibernate.eclipse/ directory/jar. This file includes a

default configuration that only logs WARN and above to a set of custom appenders (PluginFileAppender and Plu-

ginLogAppender). You can change these settings to be as verbose or silent as you please - see hibernate document-

ation for interesting categories and log4j documentation for how to configure logging via a log4j property file.

JBoss Version: 3.2.0.GA

4.1. Introduction

Ant Tools

The hibernate-tools.jar contains the core for the Hibernate Tools. It is used as the basis for both the Ant tasks de-

scribed in this document and the eclipse plugins both available from tools.hibernate.org The hibernate-tools.jar is

located in your eclipse plugins directory at /plugins/org.hibernate.eclipse.x.x.x/lib/tools/hibernate-tools.jar.

This jar is 100% independent from the eclipse platform and can thus be used independently of eclipse.

Note

There might be incompabilities with respect to the Hibernate3.jar bundled with the tools and your own jar.

Thus to avoid any confusion it is recommended to use the hibernate3.jar & hibernate-annotations.jar

bundled with the tools when you want to use the Ant tasks. Do not worry about using e.g. Hibernate 3.2

jar's with e.g. an Hibernate 3.1 project since the output generated will work with previous Hibernate 3 ver-

sions.

4.2. The<hibernatetool>ant Task

To use the ant tasks you need to have the hibernatetool task defined. That is done in your build.xml by inserting the

following xml (assuming the jars are in the lib directory):

</path>

<taskdef name="hibernatetool"

classname="org.hibernate.tool.ant.HibernateToolTask"

classpathref="toolslib" />

this <taskdef>defines a Ant task called <hibernatetool>which now can be used anywhere in your ant build.xml

files. It is important to include all the Hibernate Tools dependencies as well as the jdbc driver.

Notice that to use the annotation based Configuration you must get a release [http://annotations.hibernate.org].

When using the <hibernatetool> task you have to specify one or more of the following:

<hibernatetool

JBoss Version: 3.2.0.GA

destdir="defaultDestinationDirectory"

templatepath="defaultTemplatePath"

Ant Tools

(1)

(2)

(3)

(4)

(<configuration ...>|<annotationconfiguration ...>| (5)

<jpaconfiguration ...>|<jdbcconfiguration ...>)

(<hbm2java>,<hbm2cfgxml>,<hbmtemplate>,...*)

</hibernatetool>

(6)

(1) destdir (required): destination directory for files generated with exporters.

(2) templatepath (optional): A path to be used to look up user-edited templates.

(3) classpath (optional): A classpath to be used to resolve resources, such as mappings and usertypes. Optional,

but very often required.

(4) propertyand propertyset (optional): Used to set properties to control the exporters. Mostly relevant for

providing custom properties to user defined templates.

(5) One of 4 different ways of configuring the Hibernate Meta Model must be specified.

(6) One or more of the exporters must be specified

4.2.1. Basic examples

The following example shows the most basic setup for generating pojo's via hbm2javafrom a normalhibern-

ate.cfg.xml.The output will be put in the ${build.dir}/generated directory.

</hibernatetool>

The following example is similar, but now we are performing multiple exports from the same configuration. We

are exporting the schema via hbm2dll, generates some DAO code via <hbm2dao> and finally runs a custom code

generation via <hbmtemplate> . This is again from a normal hibernate.cfg.xml and the output is still put in the

${build.dir}/generateddirectory. Furthermore the example also shows where a classpath is specified when you

e.g. have custom usertypes or some mappings that is needed to be looked up as a classpath resource.

</classpath>

<hbmtemplate

filepattern="{package-name}/I{class-name}Constants.java"

templatepath="${etc.dir}/customtemplates"

template="myconstants.vm"

</hibernatetool>

4.3. Hibernate Configurations

JBoss Version: 3.2.0.GA

Ant Tools

hibernatetool supports four different Hibernate configurations: A standard Hibernate configuration (

<configuration> ), Annotation based configuration ( <annotationconfiguration> ), JPA persistence based config-

uration ( <jpaconfiguration> ) and a JDBC based configuration ( <jdbcconfiguration> ) for use when reverse en-

gineering.

Each have in common that they are able to build up a Hibernate Configuration object from which a set of export-

ers can be run to generate various output. Note: output can be anything, e.g. specific files, statments execution

against a database, error reporting or anything else that can be done in java code.

The following section decribes what the the various configuration can do, plus list the individual settings they have.

4.3.1. Standard Hibernate Configuration (<configuration>)

A <configuration> is used to define a standard Hibernate configuration. A standard Hibernate configuration reads

the mappings from a cfg.xml and/or a fileset.

<configuration

configurationfile="hibernate.cfg.xml"

propertyfile="hibernate.properties"

entityresolver="EntityResolver classname"

namingstrategy="NamingStrategy classname"

<fileset...>

(1)

(2)

(3)

(4)

(5)

</configuration>

(1) configurationfile (optional): The name of a Hibernate configuration file, e.g. "hibernate.cfg.xml"

(2) propertyfile (optional): The name of a property file, e.g. "hibernate.properties"

(3) entity-resolver (optional): name of a class that implements org.xml.sax.EntityResolver. Used if the map-

ping files require custom entity resolver.

(4) namingstrategy (optional): name of a class that implements org.hibernate.cfg.NamingStrategy. Used for set-

ting up the naming strategy in Hibernate which controls the automatic naming of tables and columns.

(5) A standard Ant fileset. Used to include hibernate mapping files.Remember that if mappings are already spe-

cified in the hibernate.cfg.xml then it should not be included via the fileset as it will result in duplicate import

exceptions.

4.3.1.1. Example

This example shows an example where no hibernate.cfg.xml exists, and a hibernate.properties + fileset is

used instead.

Note

Hibernate will still read any global /hibernate.propertiesavailable in the classpath, but the specified

properties file here will override those values for any non-global property.

JBoss Version: 3.2.0.GA

</fileset>

</configuration>

</hibernatetool>

Ant Tools

4.3.2. Annotation based Configuration (<annotationconfiguration>)

An <annotationconfiguration> is used when you want to read the metamodel from EJB3/Hibernate Annotations

based POJO's. To use it remember to put the jars file needed for using hibernate annotations in the classpath of the

<taskdef>.

The <annotationconfiguration> supports the same attributes as an <configuration> except that the configuration-

file attribute is now required as that is from where an AnnotationConfiguration gets the list of classes/packages it

should load.

Thus the minimal usage is:

<annotationconfiguration

configurationfile="hibernate.cfg.xml"/>

</hibernatetool>

4.3.3. JPA based configuration (<jpaconfiguration>)

An <jpaconfiguration> is used when you want to read the metamodel from JPA/Hibernate Annotation where you

want to use the auto-scan configuration as defined in the JPA spec (part of EJB3). In other words, when you do not

have a hibernate.cfg.xml, but instead have a setup where you use a persistence.xml packaged in an JPA compliant

manner.

<jpaconfiguration> will simply just try and auto-configure it self based on the available classpath, e.g. look for

META-INF/persistence.xml.

The persistenceunit attribute can be used to select a specific persistence unit. If no persistenceunit is specified it

will automatically search for one and if a unique one is found use it, but if multiple persistence units are available it

will error.

To use an <jpaconfiguration> you will need to specify some additional jars from Hibernate EntityManager in the

<taskdef> of the hibernatetool. The following shows a full setup:

</path>

JBoss Version: 3.2.0.GA

<taskdef name="hibernatetool"

Ant Tools

classname="org.hibernate.tool.ant.HibernateToolTask"

classpathref="jpatoolslib" />

<!-- it is in this classpath you put your classes dir,

and/or jpa persistence compliant jar -->

</classpath>

</hibernatetool>

Note

ejb3configuration were the name used in previous versions. It still works but will emit a warning telling

you to use jpaconfiguration instead.

4.3.4. JDBC Configuration for reverse engineering (<jdbcconfiguration>)

A <jdbcconfiguration>is used to perform reverse engineering of the database from a JDBC connection.

This configuration works by reading the connection properties from

The <jdbcconfiguration>has the same attributes as a <configuration>plus the following additional attributes:

<jdbcconfiguration

...

packagename="package.name"

revengfile="hibernate.reveng.xml"

(1)

(2)

reversestrategy="ReverseEngineeringStrategy classname"(3)

detectmanytomany="true|false"

detectoptmisticlock="true|false"

...

(4)

(5)

</jdbcconfiguration>

(1) packagename (optional): The default package name to use when mappings for classes is created

(2) revengfile (optional): name of reveng.xml that allows you to control various aspects of the reverse engineer-

ing.

(3) reversestrategy

(optional):

name

class

that

implements

org.hibernate.cfg.reveng.ReverseEngineeringStrategy. Used for setting up the strategy the tools will

use to control the reverse engineering, e.g. naming of properties, which tables to include/exclude etc. Using a

class instead of (or as addition to) a reveng.xml file gives you full programmatic control of the reverse engin-

eering.

(4) detectManytoMany (default:true): If true (the default) tables which are pure many-to-many link tables will be

mapped as such. A pure many-to-many table is one which primary-key contains has exactly two foreign-keys

pointing to other entity tables and has no other columns.

(5) detectOptimisticLock (efault:true): If true columns named VERSION or TIMESTAMP with appropriate types

will be mapped with the apropriate optimistic locking corresponding to <version> or <timestamp>

JBoss Version: 3.2.0.GA

4.3.4.1. Example

Ant Tools

Here is an example of using <jdbcconfiguration> to generate Hibernate xml mappings via <hbm2hbmxml>. The

connection settings is here read from a hibernate.propertiesfile but could just as well have been read from a hi-

bernate.cfg.xml.

</hibernatetool>

4.4. Exporters

Exporters is the parts that does the actual job of converting the hibernate metamodel into various artifacts, mainly

code. The following section describes the current supported set of exporters in the Hibernate Tool distribution. It is

also possible for userdefined exporters, that is done through the <hbmtemplate>exporter.

4.4.1. Database schema exporter (<hbm2ddl>)

<hbm2ddl> lets you run schemaexport and schemaupdate which generates the appropriate SQL DDL and allow

you to store the result in a file or export it directly to the database. Remember that if a custom naming strategy is

needed it is placed on the configuration element.

<hbm2ddl

export="true|false"

update="true|false"

drop="true|false"

create="true|false"

outputfilename="filename.ddl"

delimiter=";"

format="true|false"

haltonerror="true|false"

(1)

(2)

(3)

(4)

(5)

(6)

(7)(8)

(1) export (default: true): Execute the generated statements against the database

(2) update(default: false): Try and create an update script representing the "delta" between what is in the database

and what the mappings specify. Ignores create/update attributes. (Do *not* use against production databases,

no guarantees at all that the proper delta can be generated nor that the underlying database can actually ex-

ecute the needed operations)

(3) drop (default: false): Output will contain drop statements for the tables, indices & constraints

(4) create (default: true): Output will contain create statements for the tables, indices & constraints

(5) outputfilename (Optional): If specified the statements will be dumped to this file.

(6) delimiter (default: ";"): What delimter to use to separate statements

(7) format (default: false): Apply basic formatting to the statements.

(8) haltonerror (default: false): Halt build process if an error occurs.

4.4.1.1. Example

Basic example of using <hbm2ddl>, which does not export to the database but simply dumps the sql to a file

JBoss Version: 3.2.0.GA

named sql.ddl.

Ant Tools

</hibernatetool>

4.4.2. POJO java code exporter (<hbm2java>)

<hbm2java> is a java codegenerator. Options for controlling wether JDK 5 syntax can be used and wether the

POJO should be annotated with EJB3/Hibernate Annotations.

<hbm2java

jdk5="true|false"

ejb3="true|false"

(1)

(2)

(1) jdk (default: false): Code will contain JDK 5 constructs such as generics and static imports

(2) ejb3 (default: false): Code will contain EJB 3 features, e.g. using annotations from javax.persistence and

org.hibernate.annotations

4.4.2.1. Example

Basic example of using <hbm2java> to generate POJO's that utilize jdk5 constructs.

</hibernatetool>

4.4.3. Hibernate Mapping files exporter (<hbm2hbmxml>)

<hbm2hbmxml> generates a set of .hbm files. Intended to be used together with a <jdbcconfiguration> when per-

forming reverse engineering, but can be used with any kind of configuration. e.g. to convert from annotation based

pojo's to hbm.xml. Note that not every possible mapping transformation is possible/implemented (contributions

welcome) so some hand editing might be necessary.

4.4.3.1. Example

Basic usage of <hbm2hbmxml>.

</hibernatetool>

<hbm2hbmxml> is normally used with a <jdbcconfiguration> like in the above example, but any other configura-

tion can also be used to convert between the different ways of performing mappings. Here is an example of that,

using an <annotationconfiguration>.

JBoss Version: 3.2.0.GA

Note

Ant Tools

Not all conversions is implemented (contributions welcome), so some hand editing might be necessary.

</hibernatetool>

4.4.4. Hibernate Configuration file exporter (<hbm2cfgxml>)

<hbm2cfgxml> generates a hibernate.cfg.xml. Intended to be used together with a <jdbcconfiguration> when per-

forming reverse engineering, but can be used with any kind of configuration. The <hbm2cfgxml> will contain the

properties used and adds mapping entries for each mapped class.

<hbm2cfgxml

ejb3="true|false"

(1)

(1) ejb3 (default: false): the generated cfg.xml will have <mapping class=".."/>, opposed to <mapping re-

source="..."/> for each mapping.

4.4.5. Documentation exporter (<hbm2doc>)

<hbm2doc> generates html documentation a'la javadoc for the database schema et.al.

4.4.6. Query exporter (<query>)

<query> is used to execute a HQL query statements and optionally send the output to a file. Can be used for veri-

fying the mappings and for basic data extraction.

<query

destfile="filename">

<hql>[a HQL query string]</hql>

</query>

Currently one session is opened and used for all queries and the query is executed via the list() method. In the fu-

ture more options might become available, like performing executeUpdate(), use named queries etc.

4.4.6.1. Examples

Simplest usage of <query> will just execute the query without dumping to a file. This can be used to verify that

queries can actually be performed.

JBoss Version: 3.2.0.GA

<query>from java.lang.Object</query>

</hibernatetool>

Ant Tools

Multiple queries can be executed by nested <hql> elements. In this example we also let the output be dumped to

queryresult.txt.

Note

Currently the dump is simply a call to toString on each element.

<hql>select c.name from Customer c where c.age > 42</hql>

</hibernatetool>

4.4.7. Generic Hibernate metamodel exporter (<hbmtemplate>)

Generic exporter that can be controlled by a user provided template or class.

<hbmtemplate

filepattern="{package-name}/{class-name}.ftl"

template="somename.ftl"

exporterclass="Exporter classname"

Note

Previous versions of the tools used Velocity. We are now using Freemarker which provides us much better

exception and error handling.

4.4.7.1. Exporter via<hbmtemplate>

The following is an example of reverse engineering via <jdbcconfiguration> and use a custom Exporter via the

<hbmtemplate>.

<jdbcconfiguration

configurationfile="hibernate.cfg.xml"

packagename="my.model"/>

<hbmtemplate

exporterclass="my.own.Exporter"

filepattern="."/>

</hibernatetool>

JBoss Version: 3.2.0.GA

Ant Tools

4.5. Using properties to configure Exporters

Exporters can be controlled by user properties. The user properties is specificed via <property> or <propertyset>

and each exporter will have access to them directly in the templates and via Exporter.setProperties().

4.5.1.<property>and<propertyset>

The <property> allows you bind a string value to a key. The value will be available in the templates via $<key>.

The following example will assign the string value "true" to the variable $descriptors

Most times using <property> is enough for specifying the properties needed for the exporters. Still the ant tools

supports the notion of <propertyset>. The functionallity of <propertyset>is explained in detail in the Ant task

manual.

4.5.2. Getting access to user specific classes

If the templates need to access some user class it is possible by specifying a "toolclass" in the properties.

Placing the above <property>tag in <hibernatetool>or inside any exporter will automatically create an instance

of x.y.z.NameOfToolClass and it will be available in the templates as $sometool. This is usefull to delegate logic

and code generation to java code instead of placing such logic in the templates.

4.5.2.1. Example

Here is an example that uses <hbmtemplate> together with <property> which will be available to the templates/ex-

porter.

Note

This example actually simulates what <hbm2java> actually does.

<configuration

configurationfile="etc/hibernate.cfg.xml"/>

<hbmtemplate

templateprefix="pojo/"

template="pojo/Pojo.ftl"

filepattern="{package-name}/{class-name}.java">

</hbmtemplate>

</hibernatetool>

JBoss Version: 3.2.0.GA

Controlling reverse engineering

When using the <jdbcconfiguration> the ant task will read the database metadata and from that perform a reverse

engineering of the database schema into a normal Hibernate Configuration. It is from this object e.g.

<hbm2java>can generate other artifacts such as .java, .hbm.xml etc.

To govern this process Hibernate uses a reverse engineering strategy. A reverse engineering strategy is mainly

called to provide more java like names for tables, column and foreignkeys into classes, properties and associations.

It also used to provide mappings from SQL types to Hibernate types. The strategy can be customized by the user.

The user can even provide its own custom reverse engineering strategy if the provided strategy is not enough, or

simply just provide a small part of the strategy and delegate the rest to the default strategy.

5.1. Default reverse engineering strategy

The default strategy uses some rules for mapping JDBC artifact names to java artifact names. It also provide basic

typemappings from JDBC types to Hibernate types. It is the default strategy that uses the packagename attribute to

convert a table name to a fully qualified classname.

5.2. hibernate.reveng.xml file

To have fine control over the process a hibernate.reveng.xml file can be provided. In this file you can specify type

mappings and table filtering. This file can be created by hand (its just basic XML) or you can use the Hibernate

plugins which have a specialized editor.

Note

Many databases is case-sensitive with their names and thus if you cannot make some table match and you

are sure it is not excluded by a <table-filter>then check if the case matches; most databases stores table

names in uppercase.

The following is an example of a reveng.xml. Following the example is more details about the format.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-reverse-engineering

SYSTEM "http://hibernate.sourceforge.net/hibernate-reverse-engineering-3.0.dtd" >

<hibernate-reverse-engineering>

<type-mapping>

<sql-type jdbc-type="VARCHAR" length='20' hibernate-type="SomeUserType" />

<sql-type jdbc-type="VARCHAR" length='1' hibernate-type="yes_no" />

<sql-type jdbc-type="NUMERIC" precision='1' hibernate-type="boolean" />

JBoss Version: 3.2.0.GA

Controlling reverse engineering

<!-- the type-mappings are ordered. This mapping will be consulted last,

thus overriden by the previous one if precision=1 for the column -->

<sql-type jdbc-type="NUMERIC" hibernate-type="long" />

</type-mapping>

<table-filter match-name="BIN$.*" exclude="true" />

<table-filter match-name="DoNotWantIt" exclude="true" />

<table-filter match-catalog="BAD" match-schema="SCHEMA" match-name=".*" exclude="true" />

<!-- table allows you to override/define how reverse engineering

are done for a specific table -->

<primary-key>

<param name="table">seq_table</param>

</generator>

<key-column name="CUSTID"/>

</primary-key>

<foreign-key constraint-name="ORDER_CUST">

<many-to-one property="customer"/>

</foreign-key>

</table>

</hibernate-reverse-engineering>

5.2.1. Schema Selection (<schema-selection>)

<schema-selection> is used to drive which schema's the reverse engineering will try and process.

By default the reverse engineering will read all schemas and then use <table-filter> to decide which tables get re-

verse engineered and which do not; this makes it easy to get started but can be inefficient on databases with many

schemas.

With <schema-selection> it is thus possible to limit the actual processed schemas and thus significantly speed-up

the reverse engineering. <table-filter> is still used to then decide which tables will be included/excluded.

Note

If no <schema-selection>is specified, the reverse engineering works as if all schemas should be pro-

cessed.

This is equal to:

<schema-selection/>

which in turn is equal to:

<schema-selection match-catalog=".*" match-schema=".*" match-table=".*"/>

JBoss Version: 3.2.0.GA

5.2.1.1. Examples

Controlling reverse engineering

The following will process all tables from "MY_SCHEMA".

<schema-selection match-schema="MY_SCHEMA"/>

It is possible to have multiple schema-selection's to support multi-schema reading or simply to limit the pro-

cessing to very specific tables. The following example process all tables in "MY_SCHEMA", a specific "CITY" ta-

ble plus all tables that starts with "CODES_ in COMMON_SCHEMA".

<schema-selection match-schema="MY_SCHEMA"/>

<schema-selection match-schema="COMMON_SCHEMA" match-table="CITY"/>

<schema-selection match-schema="COMMON_SCHEMA" match-table="CODES_.*"/>

5.2.2. Type mappings (<type-mapping>)

The <type-mapping> section specifies how the JDBC types found in the database should be mapped to Hibernate

types. e.g. java.sql.Types.VARCHAR with a length of 1 should be mapped to the Hibernate type yes_noor

java.sql.Types.NUMERIC should generally just be converted to the Hibernate type long.

<type-mapping>

<sql-type

jdbc-type="integer value or name from java.sql.Types"

length="a numeric value"

precision="a numeric value"

scale="a numeric value"

not-null="true|false"

hibernate-type="hibernate type name"

</type-mapping>

The number of attributes specificed and the sequence of the sql-type's is important. Meaning that Hibernate will

search for the most specific first, and if no specific match is found it will seek from top to bottom when trying to

resolve a type mapping.

5.2.2.1. Example

The following is an example of a type-mapping which shows the flexibility and the importance of ordering of the

type mappings.

<type-mapping>

<sql-type jdbc-type="NUMERIC" precision="15" hibernate-type="big_decimal"/>

<sql-type jdbc-type="NUMERIC" not-null="true" hibernate-type="long" />

<sql-type jdbc-type="NUMERIC" not-null="false" hibernate-type="java.lang.Long" />

<sql-type jdbc-type="VARCHAR" length="1" not-null="true" hibernate-type="java.lang.Character"/>

<sql-type jdbc-type="VARCHAR" hibernate-type="your.package.TrimStringUserType"/>

<sql-type jdbc-type="VARCHAR" length="1" hibernate-type="char"/>

<sql-type jdbc-type="VARCHAR" hibernate-type="string"/>

</type-mapping>

The following table shows how this affects an example table named CUSTOMER:

Table 5.1. sql-type examples

JBoss Version: 3.2.0.GA

Column

jdbc-type

INTEGER

Controlling reverse engineering

lengt pre- not- Resulting hi-

h cisio null bernate-type

10 true int

Rationale

Nothing defined for INTEGER.

Falling back to default behavior.

NAME

INITIAL

CODE

SALARY

VARCHAR

NUMERIC

false your.package.T

rimStringUser-

Type

false char

true java.lang.Chara

cter

15 false big_decimal

No type-mapping matches

length=30 and not-null=false, but

type-mapping matches the 2 map-

pings which only specifies

VARCHAR. The type-mapping

that comes first is chosen.

Even though there is a generic

match for VARCHAR, the more

specifc type-mapping for

VARCHAR with not-null="false"

is chosen. The first VARCHAR

sql-type matches in length but has

no value for not-null and thus is

not considered.

The most specific VARCHAR

with not-null="true" is selected.

There is a precise match for NU-

MERIC with precision 15

AGE

NUMERIC

false java.lang.Long type-mapping for NUMERIC

with not-null="false"

5.2.3. Table filters (<table-filter>)

The <table-filter> let you specifcy matching rules for performing general filtering/setup for tables, e.g. let you in-

clude or exclude specific tables based on the schema or even a specifc prefix.

<table-filter

match-catalog="catalog_matching_rule"

match-schema="schema_matching_rule"

match-name="table_matching_rule"

exclude="true|false"

package="package.name"

(1)

(2)

(3)

(4)

(5)

(1) match-catalog (default: .*): Pattern for matching catalog part of the table

(2) match-schema (default: .*): Pattern for matching schema part of the table

(3) match-table (default: .*): Pattern for matching table part of the table

(4) exclude (default: false): if true the table will not be part of the reverse engineering

(5) package (default: ""): The default package name to use for classes based on tables matched by this table-filter

JBoss Version: 3.2.0.GA

Controlling reverse engineering

5.2.4. Specific table configuration (<table>)

<table> allows you to provide explicit configuration on how a table should be reverse engineered. Amongst other

things it allow control over the naming of a class for the table, specify which identifier generator should be used for

the primary key etc.

<table

catalog="catalog_name"

schema="schema_name"

name="table_name"

class="ClassName"

<primary-key.../>

<column.../>

<foreign-key.../>

</table>

(1)

(2)

(3)

(4)

(1) catalog (Optional): Catalog name for table. Has to be specified if you are reverse engineering multiple cata-

logs or if it is not equal to hiberante.default_catalog

(2) schema (Optional): Schema name for table. Has to be specified if you are reverse engineering multiple

schemas or if it is not equal to hiberante.default_schema

(3) name (Required): Name for table

(4) clase (Optional): The class name for table. Default name is camelcase version of the table name.

5.2.4.1. <primary-key>

A <primary-key> allows you to define a primary-key for tables that does not have such defined in the database,

and probably more importantly it allows you to define which identifier strategy that should be used (even for

already existing primary-key's).

<primary-key

(1)

<param name="param_name">parameter value</param> (2)

</generator>

<key-column...>

</primary-key>

(3)

(1) generator/class (Optional): defines which identifier generator should be used. The class name is any hibernate

short hand name or fully quailfied class name for an identifier strategy.

(2) generator/param (Optional): Allows to specify which parameter with name and value should be passed to the

identifier generator

(3) key-column (Optional): Specifies which column(s ) the primary-key consists of. A key-column is same as

column, but does not have the exclude property.

5.2.4.2. <column>

With a <column> it is possible to explicitly name the resulting property for a column. It is also possible to redefine

what jdbc and/or Hibernate type a column should be processed and finally it is possible to completely exclude a

column from processing.

<column

name="column_name"

jdbc-type="java.sql.Types type"

JBoss Version: 3.2.0.GA

(1)

(2)

type="hibernate_type"

property="propertyName"

exclude="true|false"

(1) name (Required): Column name

Controlling reverse engineering

(3)

(4)

(5)

(2) jdbc-type (Optional): Which jdbc-type this column should be processed as. A value from java.sql.Types,

either numerical (93) or the constant name (TIMESTAMP).

(3) type (Optional): Which hibernate-type to use for this specific column.

(4) property (Optional): What property name will be generated for this column.

(5) exclude (default: false): set to true if this column should be ignored.

5.2.4.3. <foreign-key>

The <foreign-key> has two purposes. One for allowing to define foreign-keys in databases that does not support

them or does not have them defined in their schema. Secondly, to allow defining the name of the resulting proper-

ties (many-to-one and one-to-many's).

Note

<foreign-key

constraint-name="foreignKeyName"

foreign-catalog="catalogName"

foreign-schema="schemaName"

foreign-table="tableName"

(1)

(2)

(3)

(4)

<column-ref local-column="columnName" foreign-column=(5)"foreignColumnName"/>

<many-to-one

property="aPropertyName"

exclude="true|false"/>

<set

property="aCollectionName"

exclude="true|false"/>

</foreign-key>

(6)

(7)

(1) constraint-name (Required): Name of the foreign key constraint. Important when naming many-to-one and

set. It is the constraint-name that is used to link the processed foreign-keys with the resulting property names.

(2) foreign-catalog (Optional): Name of the foreign table's catalog. (Only relevant if you want to explicitly define

a foreign key)

(3) foreign-schema (Optional): Name of the foreign table's schema. (Only relevant if you want to explicitly

define a foreign key)

(4) foreign-table (Optional): Name of the foreign table. (Only relevant if you want to explicitly define a foreign

key)

(5) column-ref (Optional): Defines that the foreign-key constraint between a local-column and foreign-column

name. (Only relevant if you want to explicitly define a foreign key)

(6) many-to-one (Optional): Defines that a many-to-one should be created and the property attribute specifies the

name of the resulting property. Exclude can be used to explicitly define that it should be created or not.

(7) set (Optional): Defines that a set should be created based on this foreign-key and the property attribute spe-

cifies the name of the resulting (set) property. Exclude can be used to explicitly define that it should be cre-

ated or not.

JBoss Version: 3.2.0.GA

5.3. Custom strategy

Controlling reverse engineering

It is possible to implement a user strategy. Such strategy must implement

org.hibernate.cfg.reveng.ReverseEngineeringStrategy. It is recommended that one uses the DelegatingReverseEn-

gineeringStrategy and provide a public constructor which takes another ReverseEngineeringStrategy as argument.

This will allow you to only implement the relevant methods and provide a fallback strategy. Example of custom

delegating strategy which converts all column names that ends with "PK" into a property named "id".

public class ExampleStrategy extends DelegatingReverseEngineeringStrategy {

public ExampleStrategy(ReverseEngineeringStrategy delegate) {

super(delegate);

}

public String columnToPropertyName(TableIdentifier table, String column) {

if(column.endsWith("PK")) {

return "id";

} else {

return super.columnToPropertyName(table, column);

}

5.4. Custom Database Metadata

By default the reverse engineering is performed by reading using the JDBC database metadata API. This is done

via the class org.hibernate.cfg.reveng.dialect.JDBCMetaDataDialect which is an implementation of

org.hibernate.cfg.reveng.dialect.MetaDataDialect.

The default implementation can be replaced with an alternative implementation by setting the property hibernat-

etool.metadatadialect to a fully qualified classname for a class that implements JDBCMetaDataDialect.

This can be used to provide database specific optimized metadata reading. If you create an optimized/better

metadata reading for your database it will be a very welcome contribution.

JBoss Version: 3.2.0.GA

Controlling POJO code generation

When using <hbm2java> or the eclipse plugin to generate POJO java code you have the possibility to control cer-

tain aspects of the code generation. This is primarily done through the <meta> tag in the mapping files. The follow-

ing section describes the possible meta tags and their use.

6.1. The<meta>attribute

The <meta> tag is a simple way of annotating the hbm.xml with information, so tools have a natural place to store/

read information that is not directly related to the Hibernate core.

You can use the <meta> tag to e.g. tell hbm2java to only generate "protected" setters, have classes always imple-

ment a certain set of interfaces or even have them extend a certain base class and even more.

The following example shows how to use various <meta> attributes and the resulting java code.

Javadoc for the Person class

@author Frodo

</meta>

</id>

</property>

</class>

The above hbm.xml will produce something like the following (code shortened for better understanding). Notice the

Javadoc comment and the protected set methods:

// default package

import java.io.Serializable;

import org.apache.commons.lang.builder.EqualsBuilder;

import org.apache.commons.lang.builder.HashCodeBuilder;

import org.apache.commons.lang.builder.ToStringBuilder;

/**

Javadoc for the Person class

@author Frodo

public class Person implements Serializable, IAuditable {

public Long id;

JBoss Version: 3.2.0.GA

public String name;

Controlling POJO code generation

}

public Person(java.lang.String name) {

this.name = name;

}

public Person() {

}

public java.lang.Long getId() {

return this.id;

}

protected void setId(java.lang.Long id) {

this.id = id;

}

/**

* The name of the person

public java.lang.String getName() {

return this.name;

}

public void setName(java.lang.String name) {

this.name = name;

}

Table 6.1. Supported meta tags

Attribute

class-description

field-description

interface

implements

extends

generated-class

scope-class

scope-set

scope-get

scope-field

default-value

use-in-tostring

use-in-equals

JBoss Version: 3.2.0.GA

Description

inserted into the javadoc for classes

inserted into the javadoc for fields/properties

If true an interface is generated instead of an class.

interface the class should implement

class the class should extend (ignored for subclasses)

overrule the name of the actual class generated

scope for class

scope for setter method

scope for getter method

scope for actual field

default initializatioin value for a field

include this property in the toString()

include this property in the equals() and hashCode() meth-

od. If no use-in-equals is specificed, no equals/hashcode will

be generated.

Attribute

gen-property

property-type

class-code

extra-import

Controlling POJO code generation

Description

property will not be generated if false (use with care)

Overrides the default type of property. Use this with any tag's

to specify the concrete type instead of just Object.

Extra code that will inserted at the end of the class

Extra import that will inserted at the end of all other imports

Attributes declared via the <meta> tag are per default "inherited" inside an hbm.xml file.

What does that mean? It means that if you e.g want to have all your classes implement IAuditable then you just

add an <meta attribute="implements">IAuditable</meta> in the top of the hbm.xml file, just after

<hibernate-mapping>. Now all classes defined in that hbm.xml file will implement IAuditable!

Note

This applies to all <meta>-tags. Thus it can also e.g. be used to specify that all fields should be declare pro-

tected, instead of the default private. This is done by adding <meta attrib-

ute="scope-field">protected</meta> at e.g. just under the <class>tag and all fields of that class will

be protected.

To avoid having a <meta> tag inherited then you can simply specify inherit = "false" for the attribute, e.g. <meta

attribute = "scope-class" inherit = "false">public abstract</meta> will restrict the "class-scope" to the current

class, not the subclasses.

6.1.1. Recomendations

The following are some good practices when using <meta> attributes.

6.1.1.1. Dangers of a class leveluse-in-string and use-in-equalsmeta attributes when having bi-

directional associations

If we have two entities with a bi-directional association between them and define at class scope level the meta at-

tributes: use-in-string, use-in-equals:

<hibernate-mapping>

...

</class>

</hibernate-mapping>

and for Event.hbm file:

<hibernate-mapping>

JBoss Version: 3.2.0.GA

</id>

Controlling POJO code generation

<many-to-many column="PERSON_ID" class="events.Person"/>

</set>

</class>

</hibernate-mapping>

Then <hbm2java> will assume you want to include all properties and collections in the toString()/equals()

methods and this can result in infinite recursive calls.

To remedy this you have to decide which side of the association will include the other part (if at all) in the to-

String()/equals() methods. Therefore it is not a good practice to put at class scope such meta attributes, unless

you are defining a class without bi-directional associations

We recomend instead to add the meta attributes at the property level:

<hibernate-mapping>

</id>

</property>

<many-to-many column="PERSON_ID" class="events.Person"/>

</set>

</class>

</hibernate-mapping>

and now for Person:

<hibernate-mapping>

Javadoc for the Person class

@author Frodo

</meta>

</id>

</property>

</class>

</hibernate-mapping>

6.1.1.2. Be aware of putting at class scope level<meta>attributeuse-in-equals

JBoss Version: 3.2.0.GA

Controlling POJO code generation

For equal()/hashCode() method generation, you have to take into account that the attributes that participate on

such method definition, should take into account only attributes with business meaning (the name, social security

number, etc, but no generated id's, for example).

This is important because Java's hashbased collections, such as java.util.Set relies on equals() and hashcode() to be

correct and not change for objects in the set; this can be a problem if the id gets assigned for an object after you in-

serted it into a set.

Therefore automatically configuration the generation of equals()/hashCode() methods specifying at class scope

level the <meta> attribute use-in-equals could be a dangerous decision that could produce non expected side-

effect.

Here [http://www.hibernate.org/109.html] you can get more in-depth explanation on the subject of equals() and

hashcode().

6.1.2. Advanced<meta>attribute examples

This section shows an example for using meta attributes (including userspecific attributes) together with the code

generation features in Hibernate Tools.

The usecase being implemented is to automatically insert some pre- and post-conditions into the getter and setters

of the generated POJO.

6.1.2.1. Generate pre/post-conditions for methods

With an <meta attribute="class-code">, you can add addional methods on a given class, nevertheless such

<meta> attribute can not be used at property scope level and Hibernate Tools does not provide such <meta> attrib-

utes.

A possibly solution for this is to modify the freemarker templates responsable for generating the POJO's. If you

look inside hibernate-tools.jar, you can find the template: pojo/PojoPropertyAccessor.ftl

This file is as the named indicates used to generate property accessors for pojo's.

Extract the PojoPropertyAccessor.ftl into a local folder i.e. ${hbm.template.path}, respecting the whole path, for

example: ${hbm.template.path}/pojo/PojoPropertyAccessor.ftl

The contents of the file is something like this:

<#foreach property in pojo.getAllPropertiesIterator()>

return this.${property.name};

}

this.${property.name} = ${property.name};

}

</#foreach>

We can add conditionally pre/post-conditions on our set method generation just adding a little Freemarker syntax

to the above source code:

JBoss Version: 3.2.0.GA

Controlling POJO code generation

<#foreach property in pojo.getAllPropertiesIterator()>

return this.${property.name};

}

<#if pojo.hasMetaAttribute(property, "pre-cond")>

${c2j.getMetaAsString(property, "pre-cond",""n")}

</#if>

this.${property.name} = ${property.name};

<#if pojo.hasMetaAttribute(property, "post-cond")>

${c2j.getMetaAsString(property, "post-cond",""n")}

</#if>

}

</#foreach>

Now if in any *hbm.xml file we define the <meta> attributes: pre-cond or post-cond, their contents will be gener-

ated into the body of the relevant set method.

As an examlpe let us add a pre-condition for property name preventing no Person can have an empty name. So we

have to modify the Person.hbm.xml file like this:

<hibernate-mapping>

</id>

if ((firstName != null) && (firstName.length() == 0) ) {

throw new IllegalArgumentException("firstName can not be an empty String");

}]]>

</meta>

</property>

</class>

</hibernate-mapping>

Note

i) If you don'' use <[[CDATA[]]> you have to scape the & symbol, i.e.: &

ii). Note that we are referring to "firstName" directly and this is the parameter name not the actual field

name. If you want to refer the field you have to use "this.firstName" instead.

Finally we have to generate the Person.java class, for this we can use both Eclipse and Ant as long as you remem-

ber to set or fill in the templatepath setting. For Ant we configure <hibernatetool> task via the templatepath at-

tribute as in:

<taskdef name="hibernatetool"

classname="org.hibernate.tool.ant.HibernateToolTask"

classpathref="lib.classpath"/>

<hibernatetool destdir="${hbm2java.dest.dir}"

templatepath="${hbm.template.path}">

</classpath>

JBoss Version: 3.2.0.GA

Controlling POJO code generation

</fileset>

</configuration>

</hibernatetool>

</target>

Invoking the target <hbm2java> will generate on the ${hbm2java.dest.dir} the file: Person.java:

// default package

import java.io.Serializable;

public class Person implements Serializable {

public Long id;

public String name;

public Person(java.lang.String name) {

this.name = name;

}

public Person() {

}

public java.lang.Long getId() {

return this.id;

}

public void setId(java.lang.Long id) {

this.id = id;

}

public java.lang.String getName() {

return this.name;

}

public void setName(java.lang.String name) {

if ((name != null) && (name.length() == 0)) {

throw new IllegalArgumentException("name can not be an empty String");

}

this.name = name;

}

JBoss Version: 3.2.0.GA

posted on 2010-09-06 16:13 勒紧皮带向前冲阅读(4160) 评论(0) 编辑收藏所属分类: hibernate

新用户注册刷新评论列表


只有注册用户登录后才能发表评论。




网站导航: 博客园 IT新闻 Chat2DB C++博客博问管理
相关文章: Hibernate Tools hibernate hql distinct Hibernate中的HQL （转） Struts 2.0整合Hibernate 3.2开发注册登录系统(转) Struts 2.0整合Hibernate 3.2开发注册登录系统(转) hibernate--getCurrentSession()与openSession()的区别 hibernate--hql语句小心得 hibernate的Ehcache hibernate--使用javabean来保存查询结果 Hibernate中get和load的区别

导航

统计

常用链接

留言簿(3)

随笔分类

随笔档案

blogjava

搜索

最新评论

阅读排行榜

评论排行榜

Hibernate Tools