Hibernate中的manytomany映射实例一（多对多双向）

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ccna_zhang 2022-09-05 16:49:07 博主文章分类：SSH ©著作权

文章标签 hibernate session user exception class 文章分类 虚拟化云计算

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1：User类

public class User {
  
 private int id;
 private String name;
 private Set roles; 
 public Set getRoles() {
  return roles;
 } public void setRoles(Set roles) {
  this.roles = roles;
 } 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;
 }
}Role类为：
public class Role {
 
 private int id;
 private String name; 
 private Set users; 
 public Set getUsers() {
  return users;
 } public void setUsers(Set users) {
  this.users = users;
 } 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;
 } 
}
2：User的配置文件为：<hibernate-mapping >
  <class name="com.bjsxt.hibernate.User" table="t_user">
     <id name="id">
         <generator class="native"/>
     </id>
     <property name="name"/>
     <set name="roles" table="t_user_role">
         <key column="userid"/>
         <many-to-many class="com.bjsxt.hibernate.Role" column="roleid"/>
     </set>
  </class>
</hibernate-mapping> 
Role的配置文件为：
<hibernate-mapping >
  <class name="com.bjsxt.hibernate.Role" table="t_role">
     <id name="id">
         <generator class="native"/>
     </id>
     <property name="name"/>
     <set name="users" table="t_user_role" order-by="userid">
          <key column="roleid"/>
          <many-to-many class="com.bjsxt.hibernate.User" column="userid"/>
     </set>    
  </class>
</hibernate-mapping>3：测试程序为：
public void testSave1(){   //首先保存Role，再保存User
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   Role r1 = new Role();
   r1.setName("数据录入人员");
   session.save(r1);
   
   Role r2 = new Role();
   r2.setName("商务主管");
   session.save(r2);
   
   Role r3 = new Role();
   r3.setName("大区经理");
   session.save(r3);
   
   User u1 = new User();
   u1.setName("10");
   
   Set u1Roles = new HashSet();
   u1Roles.add(r1);
   u1Roles.add(r2);
   u1.setRoles(u1Roles);
   
   User u2 = new User();
   u2.setName("aaa");
   Set u2Roles = new HashSet();
   u2Roles.add(r2);
   u2Roles.add(r3);
   u2.setRoles(u2Roles);
   
   User u3 = new User();
   u3.setName("kjj");
   Set u3Roles = new HashSet();
   u3Roles.add(r1);
   u3Roles.add(r2);
   u3Roles.add(r3);
   u3.setRoles(u3Roles);
   
   session.save(u1);
   session.save(u2);
   session.save(u3);
  
   session.getTransaction().commit();
   
  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
 } 
//首先加载User，根据User来加载Role
 public void testLoad1(){
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   User user = (User)session.load(User.class,1);
   System.out.println(user.getName());
   
   for(Iterator iter = user.getRoles().iterator();iter.hasNext();){
    Role role = (Role)iter.next();
    System.out.println("role.name"+role.getName());
   }
   session.getTransaction().commit(); 
  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
 }
 //首先加载Role，再根据Role来加载User
 public void testLoad2(){
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   Role role = (Role) session.load(Role.class,1);
   System.out.println("role.name"+role.getName());
   for(Iterator iter = role.getUsers().iterator();iter.hasNext(); ){
    User student = (User)iter.next();
    System.out.println("student.name:"+student.getName());
   }
   session.getTransaction().commit(); 
  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
 }
}总结：
hibernate多对多关联映射(双向User<----->Role)
具体映射方式：
   <set name="roles" table="t_user_role">
            <key column="userid"/>
            <many-to-many class="com.bjsxt.hibernate.Role" column="roleid"/>
   </set>