hibernate单向多对多映射(many-to-many)XML与注解版

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)

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:

<?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.Role" table="role">          <id name="id" type="java.lang.String">             <column name="id"/>            <generator class="uuid">              </generator>          </id>          <property name="rname" column="rname"/>      </class>  </hibernate-mapping>  

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"/>     <!--                    使用<set>标签映射集合(set)，标签中的name值为对象属性名(集合roles)                    而使用table属性是用于生成第三方表名称，例：table="user_role"                    但是第三方面中的字段是自动加入的，作为外键分别指向其它表。                       所以用<key>标签设置，例：<key column="userid"/>                     意思是：在第三方表(user_role)中加入一个外键并且指向当前的映射实体类所对应的表(user)                     使用<many-to-many>来指定此映射集合所对象的类(实例类)                     并且使用column属性加入一个外键指向Role实体类所对应的表(role)       -->          <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

User表

user_role表

示例: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:

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        (?, ?)

示例:http://download.csdn.net/detail/u011781521/9834643