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详解hibernate双向多对多关联映射XML与注解版

程序员文章站 2024-02-25 17:42:57
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...

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:

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:

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:

<?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:

<?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:

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:

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:

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:

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:

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:

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。