Hibernate----@Annotation----一对多----级联

一对多,双向,"一"的一方

 

 package com.pegasus.domain;

 import java.util.HashSet;
 import java.util.Set;

 import javax.persistence.CascadeType;
 import javax.persistence.Entity;
 import javax.persistence.FetchType;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.OneToMany;
 import javax.persistence.Table;

 //在实体类的类名前
 //标注是实体
 //对应的表名
 //相当于xml的
 //<class name="com.pegasus.domain.Group" table="t_group"></class>
 @Entity
 @Table(name="t_group")
 public class Group {
     private int id;
     private String name;
     private Set<User> users = new HashSet<User>();

     //在主键的get方法前
     //标注主键,以及生成主键策略
     //相当于<id name="id"><generator class="native"></generator></id>
     @Id
     @GeneratedValue
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }

     //在一般属性的get方法前
     //一般的列名前不需要标注
     //相当于<property name="name"></property>
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }

     //在一对多"一"的一方关联的集合前
     //使用@OneToMany标注,并标明"mappedBy",即关联的"多"的一方所对应的类的属性
 //mapped by 即 inverse=true 由多一方控制

 mapped用于指定在双向关系中两个实体中被哪个实体是被关联处理的.   在你的department和employee的一对多关系中,当你指定department中的mappedBy后,你的关系只能被employee来主动维护.也就是employee级联的处理department.
     //cascade参数标明级联的方式,如果不需要级联可以省略
     //相当于<set name="users">
     //             <key column="groupId"></key>
     //             <one-to-many class="com.pegasus.domain.User"/>
         //         </set>
     @OneToMany(mappedBy="group",
         cascade={CascadeType.ALL}
         )

     public Set<User> getUsers() {
         return users;
     }
     public void setUsers(Set<User> users) {
         this.users = users;
     }
 }

 

 一对多,双向,"多"的一方

 

 package com.pegasus.domain;

 import javax.persistence.CascadeType;
 import javax.persistence.Entity;
 import javax.persistence.FetchType;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.ManyToOne;
 import javax.persistence.Table;
 //在实体类的类名前
 //标注是实体
 //对应的表名
 //相当于xml的
 //<class name="com.pegasus.domain.User" table="t_user"></class>
 @Entity
 @Table(name="t_user")
 public class User {
     private int id;
     private String name;
     private Group group;

     //在主键的get方法前
     //标注主键,以及生成主键策略
     //相当于<id name="id"><generator class="native"></generator></id>
     @Id
     @GeneratedValue
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }

     //在一般属性的get方法前
     //一般的列名前不需要标注
     //相当于<property name="name"></property>
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     //在一对多"多"的一方关联的属性get方法前
     //使用@ManyToOne标注
     //cascade参数标明级联的方式,如果不需要级联可以省略
     //相当于<many-to-one name="group" column="groupId"></many-to-one>
     @ManyToOne(cascade={CascadeType.ALL})
     public Group getGroup() {
         return group;
     }
     public void setGroup(Group group) {
         this.group = group;
     }
 }

 单元测试类

 

 package com.pegasus.domain;

 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.cfg.AnnotationConfiguration;
 import org.hibernate.tool.hbm2ddl.SchemaExport;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;

 public class HibernateORMappingTest {
     private static SessionFactory sessionFactory;

     @BeforeClass
     public static void beforeClass() {
         new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
         sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
     }
     @AfterClass
     public static void afterClass() {
         sessionFactory.close();
     }
     /**级联保存*/
     @Test
     public void testSaveUser() {
         System.out.print("begin to testSaveUser()");
         User u = new User();
         u.setName("u1");
         Group g = new Group();
         g.setName("g1");
         u.setGroup(g);
         Session s = sessionFactory.getCurrentSession();
         s.beginTransaction();
         //s.save(g);
         s.save(u);
         s.getTransaction().commit();
     }

 //  @Test
 //  public void testSaveGroup() {
 //      System.out.print("begin to testSaveGroup()");
 //      User u1 = new User();
 //      u1.setName("u1");
 //      User u2 = new User();
 //      u2.setName("u2");
 //      Group g = new Group();
 //      g.setName("g1");
 //      g.getUsers().add(u1);
 //      g.getUsers().add(u2);
 //      u1.setGroup(g);
 //      u2.setGroup(g);
 //      Session s = sessionFactory.getCurrentSession();
 //      s.beginTransaction();
 //      s.save(g);
 //      s.getTransaction().commit();
 //  }
     /**级联查询*/
     @Test
     public void testGetUser() {
         System.out.print("begin to testGetUser()");
 //      testSaveGroup();

         Session s = sessionFactory.getCurrentSession();
         s.beginTransaction();
         User u = (User)s.get(User.class, 1);

         s.getTransaction().commit();
         System.out.println(u.getGroup().getName());
     }

 //  @Test
 //  public void testDeleteUser() {
 //      System.out.print("begin to testDeleteUser()");
 //      testSaveGroup();
 //
 //      Session s = sessionFactory.getCurrentSession();
 //      s.beginTransaction();
 //      //User u = (User)s.load(User.class, 1);
 //      //u.setGroup(null);
 //      //s.delete(u);
 //      s.createQuery("delete from User u where u.id = 1").executeUpdate();
 //      s.getTransaction().commit();
 //
 //  }

     /**级联修改*/
     @Test
     public void testUpdateUser() {
         System.out.print("begin to testUpdateUser()");
 //      testSaveGroup();

         Session s = sessionFactory.getCurrentSession();
         s.beginTransaction();
         User u = (User)s.get(User.class, 1);

         s.getTransaction().commit();

         u.setName("user");
         u.getGroup().setName("group");

         Session s2 = sessionFactory.getCurrentSession();
         s2.beginTransaction();
         s2.update(u);

         s2.getTransaction().commit();
     }

     /**级联删除*/
     @Test
     public void testDeleteGroup() {
         System.out.print("begin to testDeleteGroup()");
         testSaveGroup();

         Session s = sessionFactory.getCurrentSession();
         s.beginTransaction();
         //User u = (User)s.load(User.class, 1);
         //u.setGroup(null);
         //s.delete(u);
         Group g = (Group)s.load(Group.class, 1);
         s.delete(g);
         //s.createQuery("delete from User u where u.id = 1").executeUpdate();
         s.getTransaction().commit();

     }


 //  @Test
 //  public void testSchemaExport() {
 //      new SchemaExport(new AnnotationConfiguration().configure()).create(true, true);
 //  }

 //  public static void main(String[] args) {
 //      beforeClass();
 //  }
 }

 hibernate.cfg.xml

 

 <?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>


         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
         <property name="connection.url">jdbc:mysql://localhost/hibtest</property>
         <property name="connection.username">root</property>
         <property name="connection.password">123</property>
         <property name="dialect">org.hibernate.dialect.MySQLDialect</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> -->

         <!-- Drop and re-create the database schema on startup
         <property name="hbm2ddl.auto">update</property>
          -->
         <!--

         <mapping resource="com/pegasus/domain/Group.hbm.xml"/>
          <mapping resource="com/pegasus/domain/User.hbm.xml"/>
          -->
          <mapping class="com.pegasus.domain.Group"/>
         <mapping class="com.pegasus.domain.User"/>

     </session-factory>

 </hibernate-configuration>