休眠组合键 [英] Composite Key with Hibernate

问题描述

为了生成下一个SQL代码:

In order to generate the next SQL code:

create table users (
    user_name varchar(15) not null primary key, 
    user_pass varchar(15) not null);

create table user_roles(
    username varchar(15) not null,
    role_name varchar(15) not null, 
    primary key(usernmae, rolename)
);

您可以使用以下代码:

 <?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="databaselayer.users.UserDB" table="users">
        <id name="username" type="string" column="user_name">
                <meta attribute="scope-set">public</meta>      
        </id>    
        <property name="password" type="string" column="user_pass"  not-null="true"/>
        <set name="roles" cascade="save-update" inverse="true">
                <key column="user_name"/>
                <one-to-many class="databaselayer.users.RoleDB"/>
        </set>                       
    </class>
   <class name="databaselayer.users.RoleDB" table="user_roles">
        <composite-id>
            <key-many-to-one name="username" class="databaselayer.users.UserDB" column="user_name"/>
            <key-property name="role" type="string" column="role_name"/>
        </composite-id>             
    </class>          
</hibernate-mapping>

您可能需要在类路径中包含类以及hbm映射文件.
接下来，我发布我的Ant模式目标:
注意 $ {basedir}/build/WEB-INF/classes包含* .class和* .hbm.xml文件.

You may need to have your classes as well as hbm mapping files in your classpath.
Next I post my Ant schema target:
Note ${basedir}/build/WEB-INF/classes contains both *.class and *.hbm.xml files.

<target name="schema" description="Generate DB schema from the O/R mapping files">
    <hibernatetool destdir="${basedir}">            
        <classpath path="${basedir}/build/WEB-INF/classes">
            <fileset dir="${basedir}/build/WEB-INF/classes">
            <include name="**/*"/>
        </fileset>              
        </classpath>
        <configuration configurationfile="${basedir}/hibernate.cfg.xml"/>
        <hbm2ddl 
            drop="true" 
            create="true"
            export="true"
            outputfilename="libamo2-ddl.sql"
            delimiter=";"
            format="true"/>       
    </hibernatetool>
</target>

Hibernate文档中的相关链接

复合ID
组件作为复合ID

推荐答案

在休眠文档中查找'composite-id'元素.以下内容可能至少会给您一个意图-将您的 id 元素替换为:

Look in the hibernate docs for the 'composite-id' element. The following may at least give you the intent -- replace your id element with:

<composite-id>
    <key-property name="username"/>
    <key-property name="role"/>
</composite-id>

请注意，强烈建议 将ID设置为一个单独的类(组件")，该类实现hashCode并正确地等于它，并且是可序列化的.否则，您将只有非常尴尬的方法来使用 session.get()或 session.load()查找对象.

Note that it's strongly recommended to instead make your ID a separate class ('component') that implements hashCode and equals properly, and that is Serializable. Otherwise you'll have only very awkward ways to lookup your object using session.get() or session.load().

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