Collection mapping table

Sample Tables

CREATE TABLE `core_sample_company` (
  `companyId` decimal(18,0) NOT NULL,
  `companyName` varchar(128) NOT NULL,
  `description` varchar(1024) default NULL,
  PRIMARY KEY  (`companyId`)
);

CREATE TABLE `core_sample_role` (
  `roleId` decimal(18,0) NOT NULL,
  `roleName` varchar(128) NOT NULL,
  `companyId` decimal(18,0) NOT NULL,
  `description` varchar(1024) default NULL,
  PRIMARY KEY  (`roleId`)
);

CREATE TABLE `core_sample_user` (
  `userId` decimal(18,0) NOT NULL,
  `userName` varchar(128) NOT NULL,
  `companyId` decimal(18,0) NOT NULL,
  `defaultRoleId` decimal(18,0) default NULL,
  `description` varchar(1024) default NULL,
  PRIMARY KEY  (`userId`)
);

CREATE TABLE `core_sample_user_role` (
  `userId` decimal(18,0) NOT NULL,
  `roleId` decimal(18,0) NOT NULL,
  `pripority` int(11) NOT NULL,
  PRIMARY KEY  (`userId`,`roleId`)
);

HBM defintion

The definiton of <set>, <bag>, <list> is similar.

Defines a collection whose element type is simple data type.

<class name="SampleCompany" table="core_sample_company">

        <bag name="roleNames" table="core_sample_role" lazy="false" >
            <key column="companyId"/>
            <element column="roleName" type="string"/>
        </bag>

</class>

Query HQL: select c.id, c.name, r from SampleCompany c left join c.roleNames r

Defines a collection whose element type is another mapped java class

<class name="SampleCompany" table="core_sample_company">   

   <bag name="roles" cascade="none">
            <key column="companyId"/>
            <one-to-many class="SampleRole" not-found="ignore"/>
        </bag>

</class>

Query HQL: select c.id, c.name, r.name from SampleCompany c left join c.role r

Pay attention that key column is a foreign column of SampleRole table.

Defines a list with list-index

<list> is not a popular element. It request a index column in table. The index column is the index of java List, it has to be a sequence starts from 0.

<class name="SampleUser" table="core_sample_user">

     <list name="roles" table="core_sample_user_role" cascade="all" lazy="false" >
            <key><column name="userId" sql-type="integer"/></key>
            <index column="priority"></index>
            <many-to-many class="SampleRole">
                <column name="roleId"></column>
            </many-to-many>
        </list>

</class>

The benifit of <list> is it alwasy sorts list by index column. However, It is hard to resort the list. I tried remove a role from role list and add it to another poisition. When save the role list, an exception throwed:

java.sql.BatchUpdateException: Duplicate entry 'user001-role003 for key 1

This should be a hibernate bug.

Defines a bag with relationship table

<class name="SampleRole" table="core_sample_role">

      <bag name="users" table="core_sample_user_role" cascade="none" lazy="false">
            <key><column name="roleId" sql-type="integer"/></key>
            <many-to-many class="SampleUser">
                <column name="userId"></column>
            </many-to-many>
        </bag>

</class>

• Key column is foreign column from relationship table to current table(SampleRole>
• many-to-many sub column is foreign column from relationship table to target table (SampleUser)