hibernate双向多对多关联映射XML与注解版

小咪咪 2022-06-15 21:19 271阅读 0赞

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：

![20170507164724351][]

**(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:

![20170507170902781][]

role表:

![20170507170941631][]

user\_role表:

![20170507171018563][]

示例:[http://download.csdn.net/detail/u011781521/9835781][http_download.csdn.net_detail_u011781521_9835781]

**(2)注解版**

Role类:

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
            (?, ?)

示例:[http://download.csdn.net/detail/u011781521/9835795][http_download.csdn.net_detail_u011781521_9835795]

[20170507164724351]: /images/20220616/eb31203208cb4f1892d53423cf2733f8.png
[20170507170902781]: /images/20220616/a6899e2ba0a9424dacf364aa07f1c40e.png
[20170507170941631]: /images/20220616/b09ef24df24d481a87e5dc999146a970.png
[20170507171018563]: /images/20220616/de5e3a7cc39248488bc1351c19c0970e.png
[http_download.csdn.net_detail_u011781521_9835781]: http://download.csdn.net/detail/u011781521/9835781
[http_download.csdn.net_detail_u011781521_9835795]: http://download.csdn.net/detail/u011781521/9835795