hibernate单向多对多映射(many-to-many)XML与注解版

￡神魔★判官ぃ 2022-06-16 03:56 152阅读 0赞

多对多关联映射需要新增加一张表才完成基本映射,他的实例场景如下:

用户与他的角色(一个用户拥有多个角色，一个角色还可以属于多个用户)

![20170504175206805][]

多对多关联映射,需要一个中间表,两个表中的主键放到第三张做一个关联,用第三张表来解决可能会造成数据冗余的问题,多对多的关联映射,在实体类中,跟一对多一样,也是用集合来表示的。

单向关联映射则是只能由A端去操作B端，B端不能操作A端的数据。而双向关联映射则是A，B两端都可以操作另一端的数据。

**(1)XML版**

SQL文件为:

CREATE TABLE `user` (
      `id` varchar(255) NOT NULL,
      `uname` varchar(255) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
    CREATE TABLE `role` (
      `id` varchar(255) NOT NULL,
      `rname` varchar(255) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
    CREATE TABLE `user_role` (
      `userid` varchar(255) DEFAULT NULL,
      `roleid` varchar(255) DEFAULT NULL
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Role实体类：

package Hibernate_demo1.Demo9.Entity;
    
    import java.util.Set;
    
    public class Role {
    	
    	private String id;
    	private String rname;
    
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getRname() {
    		return rname;
    	}
    	public void setRname(String rname) {
    		this.rname = rname;
    	}
    	
    	
    
    }

User实体类:

package Hibernate_demo1.Demo9.Entity;
    
    import java.util.Set;
    
    public class User {
    
    	private String id;
    	private String uname;
    	private Set<Role> roles;  //角色集合,一个用户可以有多个角色
    	
    	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;
    	}
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getName() {
    		return uname;
    	}
    	public void setName(String name) {
    		this.uname = name;
    	}
    }

Role.hbm.xml映射文件:

User.hbm.xml 映射文件:

<?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.Demo9.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.Demo9.Entity.Role" column="roleid"/>  
            </set>  
        </class>  
    </hibernate-mapping>

测试类如下:

package Hibernate_demo1.Demo9;
    
    import java.util.HashSet;
    import java.util.Set;
    
    import org.hibernate.Session;
    
    import Hibernate_demo1.Demo9.Entity.Role;
    import Hibernate_demo1.Demo9.Entity.User;
    import Hibernate_demo1.Demo9.Util.HibernateUtils;
    
    public class App 
    {
        public static void main( String[] args )
        {
        	Session session = null;
        	try{  
        		  
        	    session = HibernateUtils.getSession();
        	    session.beginTransaction();  
        	      
        	    //创建三个角色
        	    Role ro1=new Role();
        	    ro1.setRname("程序员");
        	    //保存角色
        	    session.save(ro1);
        	    
        	    Role ro2=new Role();
        	    ro2.setRname("产品经理");
        	    //保存角色
        	    session.save(ro2);
        	    
        	    
        	    Role ro3=new Role();
        	    ro3.setRname("CEO");
        	    //保存角色
        	    session.save(ro3);
        	    
        	    
        	    //创建两个用户
        	    User use1=new User();
        	    use1.setName("小明");
        	    
        	    User use2=new User();
        	    use2.setName("小黑");
        	    
        	    
        	    Set<Role> su=new HashSet();
        	    su.add(ro1);
        	    su.add(ro2);
        	    //给小明设置角色为(程序员,产品经理)
        	    use1.setRoles(su);
        	    
        	    Set<Role> su1=new HashSet();
        	    su1.add(ro3);
        	    
        	    //给小黑设置角色为(CEO)
        	    use2.setRoles(su1);
        	    
        	    session.save(use1);
        	    session.save(use2);
        	    
        	    session.getTransaction().commit();  
        	}catch(Exception e){  
        	    e.printStackTrace();  
        	    session.getTransaction().rollback();  
        	}finally{  
        	    HibernateUtils.closeSession(session);  
        	}
        }
    }

执行结果如下:

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_role
            (userid, roleid) 
        values
            (?, ?)
    Hibernate: 
        insert 
        into
            user_role
            (userid, roleid) 
        values
            (?, ?)
    Hibernate: 
        insert 
        into
            user_role
            (userid, roleid) 
        values
            (?, ?)

效果为:

Role表

![20170505164839407][]

User表

![20170505164922961][]

user\_role表

![20170505165036321][]

示例:[http://download.csdn.net/detail/u011781521/9834640][http_download.csdn.net_detail_u011781521_9834640]

**(2)注解版**

Role类

package Hibernate_demo1.Demo10.Entity;
    
    import java.util.Set;
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    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 rname;
    
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getRname() {
    		return rname;
    	}
    	public void setRname(String rname) {
    		this.rname = rname;
    	}
    }

User类

package Hibernate_demo1.Demo10.Entity;
    
    import java.util.Set;
    
    import javax.persistence.CascadeType;
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.JoinColumn;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinTable;
    import javax.persistence.ManyToMany;
    import javax.persistence.OrderBy;
    import javax.persistence.Table;
    
    
    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(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
        @JoinTable(name = "user_role", joinColumns = {@JoinColumn(name ="userid" )}, inverseJoinColumns = { @JoinColumn(name = "roleid") })
    	private Set<Role> roles;  //角色集合,一个用户可以有多个角色
    	
    	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;
    	}
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getName() {
    		return uname;
    	}
    	public void setName(String name) {
    		this.uname = name;
    	}
    	
    	
    }

测试类:

package Hibernate_demo1.Demo10;
    
    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.Demo10.Entity.Role;
    import Hibernate_demo1.Demo10.Entity.User;
    
    /**
     * Hello world!
     *
     */
    public class App 
    {
        public static void main( String[] args )
        {
        	SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();  
        	Session session = sessionFactory.getCurrentSession();  
        	Transaction tx = session.beginTransaction();  
            
    
        	//创建三个角色
    	    Role ro1=new Role();
    	    ro1.setRname("程序员");
    	    //保存角色
    	    session.save(ro1);
    	    
    	    Role ro2=new Role();
    	    ro2.setRname("产品经理");
    	    //保存角色
    	    session.save(ro2);
    	    
    	    
    	    Role ro3=new Role();
    	    ro3.setRname("CEO");
    	    //保存角色
    	    session.save(ro3);
    	    
    	    
    	    //创建两个用户
    	    User use1=new User();
    	    use1.setName("小明");
    	    
    	    User use2=new User();
    	    use2.setName("小黑");
    	    
    	    
    	    Set<Role> su=new HashSet();
    	    su.add(ro1);
    	    su.add(ro2);
    	    //给小明设置角色为(程序员,产品经理)
    	    use1.setRoles(su);
    	    
    	    Set<Role> su1=new HashSet();
    	    su1.add(ro3);
    	    
    	    //给小黑设置角色为(CEO)
    	    use2.setRoles(su1);
    	    
    	    session.save(use1);
    	    session.save(use2);
        	
            tx.commit();
            session.close();
        }
    }

执行结果如下:

示例:[http://download.csdn.net/detail/u011781521/9834643][http_download.csdn.net_detail_u011781521_9834643]

[20170504175206805]: /images/20220616/81e1a0954bfa45a884248c681f45119d.png
[20170505164839407]: /images/20220616/e1cb4dd7fcd24435ad959104da4dc434.png
[20170505164922961]: /images/20220616/c0cadd1fef3a4e899cdfb2b07359b4b8.png
[20170505165036321]: /images/20220616/2796f6c16e3541b0a6308a8d8ae001c2.png
[http_download.csdn.net_detail_u011781521_9834640]: http://download.csdn.net/detail/u011781521/9834640
[http_download.csdn.net_detail_u011781521_9834643]: http://download.csdn.net/detail/u011781521/9834643