Hibernate 使用 Annotation 4（一对多单向关联）

Group.java代码：

?
?
User.java代码：
?
?
RelationsTest.java代码：
<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration>    <session-factory>        <!-- Database connection settings -->        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>        <property name="connection.username">root</property>        <property name="connection.password">root</property>        <!-- JDBC connection pool (use the built-in) -->        <property name="connection.pool_size">100</property>        <!-- SQL dialect -->        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>        <!-- Enable Hibernate's automatic session context management -->        <property name="current_session_context_class">thread</property>        <!-- Disable the second-level cache  -->        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>         <!-- Echo all executed SQL to stdout -->        <property name="show_sql">true</property>         <property name="format_sql">true</property>        <!-- Drop and re-create the database schema on startup -->        <!--<property name="hbm2ddl.auto">create</property>--><mapping class="com.jlee04.one2moneydanxiang.User"/><mapping class="com.jlee04.one2moneydanxiang.Group"/>    </session-factory></hibernate-configuration>
?