试用JBoss Envers项目有一阵子了，趁Envers项目发布 1.1.0版，也同时把学习笔记共享给大家，希望对大家有所帮助。
下面来看一下JBoss Envers项目的目的，官方说明如下：
The Envers project aims to enable easy versioning of persistent classes.
All that you have to do is annotate your persistent class or some of its properties,
that you want to version, with @Versioned. For each versioned entity, a table will be created,
which will hold the history of changes made to the entity. You can then retrieve and
query historical data without much effort.
JBoss Envers目的是根据对实体的设置，提供记录执行数据变更历史的功能(数据变更版本)。Envers的配置非常简单，如果需要对某个实例进行历史数据版本记录，只需要在实例上配置@Versioned annotation即可。 针对每个实体的版本的历史数据,Envers都会创建一个单独的数据表进行存储。
目前Envers支持Hibernate和Hibernate-entitymanager(JPA实现)
本示例以Hibernate-entitymanager为例，讲解其配置的方法：
先配置 persistence.xml, 加入 property配置
<persistence-unit 
>
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class></class>
<properties>
<property name="hibernate.dialect" />
<!-- other hibernate properties -->
<property name="hibernate.ejb.event.post-insert"
value="org.jboss.envers.event.VersionsEventListener" />
<property name="hibernate.ejb.event.post-update"
value="org.jboss.envers.event.VersionsEventListener" />
<property name="hibernate.ejb.event.post-delete"
value="org.jboss.envers.event.VersionsEventListener" />
<property name="hibernate.ejb.event.pre-collection-update"
value="org.jboss.envers.event.VersionsEventListener" />
<property name="hibernate.ejb.event.pre-collection-remove"
value="org.jboss.envers.event.VersionsEventListener" />
<property name="hibernate.ejb.event.post-collection-recreate"
value="org.jboss.envers.event.VersionsEventListener" />
</properties>
</persistence-unit>
示例代码:
1 import org.jboss.versions.Versioned;
2
3 import javax.persistence.Entity;
4 import javax.persistence.Id;
5 import javax.persistence.GeneratedValue;
6 import javax.persistence.Column;
7
8 @Entity
9 @Versioned
10 public class Blog {
11 @Id
12 @Column(length=32)
13 private String id;
14
15 @Versioned
16 @Column(length=100)
17 private String title;
18
19 @Column(length=2000)
20 private String date;
21
22 @Versioned
23 @ManyToOne
24 private String body;
25
26 @ManyToOne
27 private Author author;
28 // add getters, setters, constructors, equals and hashCode here
29 }
30
31 @Entity
32 @Versioned
33 public class Author {
34
35 @Id
36 @Column(length=32)
37 private String id;
38
39 @Versioned
40 @Column(length=20)
41 private String name;
42
43 }
下面是进行测试的代码:
1
// 新增操作
entityManager.getTransaction().begin();
2
3 Author matthew = new Author("1", "Matthew Xie");
4 Blog newBlog = new Blog("1", "Matthew's new Blog" "TODO{add content here}", matthew);
5
6 entityManager.persist(matthew);
7 entityManager.persist(newBlog);
8
9 entityManager.getTransaction().commit();
1 //对Blog和author进行修改操作
2 entityManager.getTransaction().begin();
3
4 Author author = entityManager.find(Author.class, "1");
5 Blog blog = entityManager.find(Blog.class, "1");
6
7 // Changing the address's house number
8 author.setName("Matt Xie")
9
10 Author newAuthor = new Author("2", "newAuthor");
11
12 // change blog author to newAuthor
13 blog.setAuthor(newAuthor);
14
15 entityManager.getTransaction().commit();
1 //下面代码，演示了如何取得历史版本数据
2 VersionsReader reader = VersionsReaderFactory.get(entityManager);
3
4 // get Blog all versions id
5 List<Number> versions = reader.getRevisions(Blog.class, "1"/*blog id*/);
6 for (Number version : versions) {
7 Blog blog = reader.find(Blog.class, "1", version);
8 }
注： 补充 Hibernate Envers的Property配置说明
| org.jboss.envers.versionsTablePrefix |
|
String that will be prepended to the name of a versioned entity
to create the name of the entity, that will hold version information.
|
| org.jboss.envers.versionsTableSuffix |
_versions |
String that will be appended to the name of a versioned entity
to create the name of the entity, that will hold version information. If you version
an entity with a table name Person, in the default setting Envers will
generate a Person_versions table to store historical data.
|
| org.jboss.envers.revisionFieldName |
_revision |
Name of a field in the versions entity that will hold the revision
number. |
| org.jboss.envers.revisionTypeFieldName |
_revision_type |
Name of a field in the versions entity that will hold the type
of the revision (currently, this can be: add, mod, del). |
| org.jboss.envers.revisionOnCollectionChange |
true |
Should a revision be generated when a not-owned relation field
changes (this can be either a collection in a one-to-many relation, or the
field using "mappedBy" attribute in a one-to-one relation). |
| org.jboss.envers.warnOnUnsupportedTypes |
false |
When true, a warning in the log will be issued
when a property is versioned with an unsupported type, instead of
an exception. This way, the configuration process isn't interrupted,
but the version schema isn't complete (it lacks the unsupported
properties, which won't be versioned). |
| org.jboss.envers.unversionedOptimisticLockingField |
false |
When true, properties to be used for optimistic locking,
annotated with @Version, will be automatically unversioned (their history
won't be stored; it normally doesn't make sense to store it). |
JBoss Envers官方网址: http://www.jboss.org/envers
Good Luck!
Yours Matthew!