Hibernate annotation 一对多，多对一

package com.hibernate.entity;

import java.io.Serializable;


@Entity
public class Tgroup implements Serializable {
  
  
  /**
   * 
   */
  private static final long serialVersionUID = 1158932874414375265L;

  private int id;
  
  private String name;
  
  private Set<Tuser> tUsers = new HashSet<Tuser>();

  @Id
  @GeneratedValue
  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  @OneToMany(mappedBy="tgroup")//如果不写mappedBy，那么tuser表中，将会有两个groupid,一个是groupid，一个是tgroup_id
  //一对多的时候，按经验，最好写mappedBy。"tGroup"是TUser表中的tGroup字段
  public Set<Tuser> gettUsers() {
    return tUsers;
  }

  public void settUsers(Set<Tuser> tUsers) {
    this.tUsers = tUsers;
  }
  
}

package com.hibernate.entity;

import java.io.Serializable;

@Entity
public class Tuser implements Serializable {

  /**
   * 
   */
  private static final long serialVersionUID = -635427302186865965L;
  
  
  private int id;
  
  private String name;
  
  private Tgroup tgroup;

  @Id
  @GeneratedValue
  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  
  @ManyToOne
  @JoinColumn(name="groupid")//这样，在Tuser表中，就有一个groupid的外键与Tgroup表的id关联
  public Tgroup getTgroup() {
    return tgroup;
  }

  public void setTgroup(Tgroup tgroup) {
    this.tgroup = tgroup;
  }

  
  
}

<?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">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

  <session-factory>
    <property name="dialect">
      org.hibernate.dialect.MySQLDialect
    </property>
    <property name="connection.url">
      jdbc:mysql://localhost/test
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password">root</property>
    <property name="connection.driver_class">
      com.mysql.jdbc.Driver
    </property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</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>
    <!--
      <mapping class="com.hibernate.entity.Husband" />
      <mapping class="com.hibernate.entity.Wife" />
    -->
    <mapping class="com.hibernate.entity.Tgroup" />
    <mapping class="com.hibernate.entity.Tuser" />
  </session-factory>

</hibernate-configuration>

package com.hibernate.test;


import org.hibernate.SessionFactory;

public class ORMappingTest {
  
  private static SessionFactory sessionFactory;

  @BeforeClass
  public static void setUpBeforeClass() throws Exception {
    sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
  }

  @AfterClass
  public static void tearDownAfterClass() throws Exception {
    sessionFactory.close();
  }
  
  @Test
  public void testSchemaExport() {
    new SchemaExport(new AnnotationConfiguration().configure()).create(true, true);
  }

}