详解hibernate双向多对多关联映射XML与注解版

时间：2022-05-12 01:46:49

双向多对多关联映射原理:

假设，一个员工可能有多个角色，一个角色可能有多个员工，从员工或角色的角度看，这就是多对多的关系，不管从哪一个角度看，都是多对多的联系。多对多关联映射关系一般采用中间表的形式来实现，即新增一种包含关联双方主键的表。实现多对多关联关系，在数据库底层通过添加中间表指定关联关系，而在hibernate框架在双方的实体中添加一个保存对方的集合，在双方的映射文件中使用<set>元素和<many-to-many>元素进行关联关系的配置。

如下图所示：

详解hibernate双向多对多关联映射XML与注解版

(1)XML版

Role类:

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package Hibernate_demo1.Demo15.Entity;
 
import java.util.Set;
 
public class Role {
   
  private String id;
  private String rame;
  private Set<User> users;
   
   
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
  public String getRame() {
    return rame;
  }
  public void setRame(String rame) {
    this.rame = rame;
  }
  public Set<User> getUsers() {
    return users;
  }
  public void setUsers(Set<User> users) {
    this.users = users;
  }
}

User类:

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package Hibernate_demo1.Demo15.Entity;
 
import java.util.Set;
 
public class User {
 
  private String id;
  private String uname;
  private Set<Role> roles;
 
   
 
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
  public String getUname() {
    return uname;
  }
  public void setUname(String uname) {
    this.uname = uname;
  }
  public Set<Role> getRoles() {
    return roles;
  }
  public void setRoles(Set<Role> roles) {
    this.roles = roles;
  }
   
   
}

Role.hbm.xml映射类:

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<?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="Hibernate_demo1.Demo15.Entity.Role" table="role"> 
    <id name="id" type="java.lang.String"> 
      <column name="id"/>
      <generator class="uuid"> 
      </generator> 
    </id> 
    <property name="rame" column="rname"/>
     
    <set name="users" table="user_role"> 
      <key column="roleid"></key> 
      <many-to-many class="Hibernate_demo1.Demo15.Entity.User" column="userid"></many-to-many> 
    </set> 
  </class> 
</hibernate-mapping> 

User.hbm.xml映射类:

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<?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="Hibernate_demo1.Demo15.Entity.User" table="user"> 
    <id name="id"> 
      <generator class="uuid"> 
      </generator> 
    </id> 
     
    <property name="uname" column="uname"/> 
      
     <set name="roles" table="user_role">
      <key column="userid"/>
      <many-to-many class="Hibernate_demo1.Demo15.Entity.Role" column="roleid" />  
    </set>
  </class> 
</hibernate-mapping> 

测试类:

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package Hibernate_demo1.Demo15;
 
import java.util.HashSet;
import java.util.Set;
 
import org.hibernate.Session;
 
import Hibernate_demo1.Demo15.Entity.Role;
import Hibernate_demo1.Demo15.Entity.User;
import Hibernate_demo1.Demo15.Util.HibernateUtils;
 
 
 
public class App 
{
  public static void main( String[] args )
  {
     
    Session session = null;
    try{ 
        
      session = HibernateUtils.getSession();
      session.beginTransaction(); 
       
 
      Role r1 = new Role();
      r1.setRame("数据录入人员");
      session.save(r1);
       
      Role r2 = new Role();
      r2.setRame("商务主管");
      session.save(r2);
       
      Role r3 = new Role();
      r3.setRame("商务经理");
      session.save(r3);
       
      Role r4 = new Role();
      r4.setRame("项目会计");
      session.save(r4);
       
      User u1 = new User();
      u1.setUname("张三");
      Set<Role> u1Roles = new HashSet<Role>();
      u1Roles.add(r1);
      u1Roles.add(r2);
      u1.setRoles(u1Roles);
      session.save(u1);
       
      User u2 = new User();
      u2.setUname("李四");
      Set<Role> u2Roles = new HashSet<Role>();
      u2Roles.add(r1);
      u2Roles.add(r2);
      u2Roles.add(r3);
      u2.setRoles(u2Roles);
      session.save(u2);
       
      User u3 = new User();
      u3.setUname("王五");
      Set<Role> u3Roles = new HashSet<Role>();
      u3Roles.add(r3);
      u3Roles.add(r4);
      u3.setRoles(u3Roles);
      session.save(u3);
       
       
      session.getTransaction().commit(); 
    }catch(Exception e){ 
      e.printStackTrace(); 
      session.getTransaction().rollback(); 
    }finally{ 
      HibernateUtils.closeSession(session); 
    }
  }
}

执行结果:

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Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user
    (uname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user
    (uname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user
    (uname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)

数据库内容为:

user表:

详解hibernate双向多对多关联映射XML与注解版

role表:

详解hibernate双向多对多关联映射XML与注解版

user_role表:

详解hibernate双向多对多关联映射XML与注解版

(2)注解版

Role类:

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package Hibernate_demo1.Demo16.Entity;
 
import java.util.HashSet;
import java.util.Set;
 
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
 
import org.hibernate.annotations.GenericGenerator;
 
@Entity
@Table(name="role")
public class Role {
   
  @Id
    @GenericGenerator(name="uuidGenerator", strategy="uuid")
    @GeneratedValue(generator="uuidGenerator")
  private String id;
   
  @Column(name="rname")
  private String rame;
   
  @ManyToMany(cascade=CascadeType.REFRESH,mappedBy="roles")
  private Set<User> users=new HashSet<User>();
   
   
   
   
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
  public String getRame() {
    return rame;
  }
  public void setRame(String rame) {
    this.rame = rame;
  }
  public Set<User> getUsers() {
    return users;
  }
  public void setUsers(Set<User> users) {
    this.users = users;
  }
}

User类:

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package Hibernate_demo1.Demo16.Entity;
 
import java.util.HashSet;
import java.util.Set;
 
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
import javax.persistence.JoinColumn;
 
import org.hibernate.annotations.GenericGenerator;
 
@Entity
@Table(name="user")
public class User {
 
  @Id
    @GenericGenerator(name="uuidGenerator", strategy="uuid")
    @GeneratedValue(generator="uuidGenerator")
  private String id;
   
  @Column(name="uname")
  private String uname;
   
  /*
   * @ManyToMany表示多对多关联，对于这种关联极少数情况会使用级联删除，我这里设置的是级联刷新；
   * 因为有中间表的存在这里使用@JoinTable来设置关联表后面的name配置的是关联表的名称
   * inverseJoinColumn配置的是关系被维护一方主键对应的中间表字段
   * joinColumn配置的是关系维护方主键对应的中间表字段。
   */
  @ManyToMany(cascade=CascadeType.REFRESH)
  @JoinTable(name="user_role",inverseJoinColumns=@JoinColumn(name="roleid"),joinColumns=@JoinColumn(name="userid"))
  private Set<Role> roles=new HashSet<Role>();
 
   
 
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
  public String getUname() {
    return uname;
  }
  public void setUname(String uname) {
    this.uname = uname;
  }
  public Set<Role> getRoles() {
    return roles;
  }
  public void setRoles(Set<Role> roles) {
    this.roles = roles;
  }
   
   
}

测试类:

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package Hibernate_demo1.Demo16;
 
import java.util.HashSet;
import java.util.Set;
 
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
 
import Hibernate_demo1.Demo16.Entity.Role;
import Hibernate_demo1.Demo16.Entity.User;
 
 
public class Test {
 
  public static void main(String[] args) {
     
 
    SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); 
    Session session = sessionFactory.getCurrentSession(); 
    Transaction tx = session.beginTransaction(); 
     
   
    //创建两个用户
    User us1=new User();
    us1.setUname("小明");
     
    User us2=new User();
    us2.setUname("小黑");
     
    //创建用户集合
    Set<User> su=new HashSet<User>();
    su.add(us1);
    su.add(us2);
     
     
    //创建两个角色
    Role ro1=new Role();
    ro1.setRame("程序员");
    ro1.setUsers(su);
     
    Role ro2=new Role();
    ro2.setRame("技术经理");
    ro2.setUsers(su);
     
     
    //创建角色集合
    Set<Role> sr=new HashSet<Role>();
    sr.add(ro1);
    sr.add(ro2);
     
    //往用户添加角色集合
    us1.setRoles(sr);
    us2.setRoles(sr);
     
    //保存用户和角色
    session.save(us1);
    session.save(us2);
    session.save(ro1);
    session.save(ro2);
     
     
    tx.commit();
    session.close();
  }
 
}

执行结果如下:

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Hibernate: 
  insert 
  into
    user
    (uname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user
    (uname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    role
    (rname, id) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)
Hibernate: 
  insert 
  into
    user_role
    (userid, roleid) 
  values
    (?, ?)

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。

原文链接：http://blog.csdn.net/u011781521/article/details/71335507?utm_source=tuicool&utm_medium=referral

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