Hibernate，JPA注解@ManyToMany

@ManyToMany默认处理机制，当双向多对多关联中没有定义任何物理映射时, Hibernate根据以下规则生成相应的值：

关联表名: 主表表名+_下划线+从表表名；

关联到主表的外键名：从表用于关联的属性名+_下划线+主表中的主键列名；

关联到从表的外键名：主表用于关联的属性名+_下划线+从表的主键列名， 以上规则对于双向一对多关联同样有效。

用例代码如下：

• 数据库DDL语句

1，CAT表

 create table CAT
 (
   id          VARCHAR2(32 CHAR) not null,
   create_time TIMESTAMP(6),
   update_time TIMESTAMP(6),
   cat_name    VARCHAR2(255 CHAR),
   first_name  VARCHAR2(255 CHAR),
   last_name   VARCHAR2(255 CHAR),
   version     NUMBER(10) not null
 )

2，HOBBY表

 create table HOBBY
 (
   id          VARCHAR2(32 CHAR) not null,
   create_time TIMESTAMP(6),
   update_time TIMESTAMP(6),
   name        VARCHAR2(255 CHAR),
   cat_id      VARCHAR2(32 CHAR)
 )

• hibernate.cfg.xml

 <?xml version="1.0" encoding="utf-8" ?>
 <!DOCTYPE hibernate-configuration
  PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
  "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 <hibernate-configuration>
     <session-factory>
         <!-- 数据库驱动配置 -->
         <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
         <property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
         <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>
         <property name="connection.username">wxuatuser</property>
         <property name="connection.password">xlh</property>
         <property name="show_sql">true</property>
         <!-- 自动执行DDL属性是update，不是true -->
         <property name="hbm2ddl.auto">update</property>
         <!-- hibernate实体类 -->

         <mapping class="b11_ManyToMany.Cat"/>
         <mapping class="b11_ManyToMany.Hobby"/>

     </session-factory>
 </hibernate-configuration>

• java类

实体类 - 基类

package model;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
import org.hibernate.annotations.GenericGenerator;
/**
 * 实体类 - 基类
 */
@MappedSuperclass
public class BaseEntity implements Serializable {

    private static final long serialVersionUID = -6718838800112233445L;

    private String id;// ID
    private Date create_time;// 创建日期
    private Date update_time;// 修改日期
    @Id
    @Column(length = 32, nullable = true)
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid")
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    @Column(updatable = false)
    public Date getCreate_time() {
        return create_time;
    }
    public void setCreate_time(Date create_time) {
        this.create_time = create_time;
    }
    public Date getUpdate_time() {
        return update_time;
    }
    public void setUpdate_time(Date update_time) {
        this.update_time = update_time;
    }
    @Override
    public int hashCode() {
        return id == null ? System.identityHashCode(this) : id.hashCode();
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass().getPackage() != obj.getClass().getPackage()) {
            return false;
        }
        final BaseEntity other = (BaseEntity) obj;
        if (id == null) {
            if (other.getId() != null) {
                return false;
            }
        } else if (!id.equals(other.getId())) {
            return false;
        }
        return true;
    }
}

实体类

Cat.java

 package b11_ManyToMany;

 import java.util.Set;
 import javax.persistence.AttributeOverride;
 import javax.persistence.AttributeOverrides;
 import javax.persistence.Column;
 import javax.persistence.Embedded;
 import javax.persistence.Entity;
 import javax.persistence.FetchType;
 import javax.persistence.ManyToMany;
 import javax.persistence.Version;
 import model.BaseEntity;
 import org.hibernate.annotations.Cascade;
 import org.hibernate.annotations.DynamicInsert;
 import org.hibernate.annotations.DynamicUpdate;

 @Entity
 @DynamicInsert
 @DynamicUpdate
 public class Cat extends BaseEntity{
     /**
      * 实体类
      */
     private static final long serialVersionUID = -2776330321385582872L;

     private Set<Hobby> hobby;
     private String cat_name;
     private Name name;
     private int version;

     @Version
     public int getVersion() {
         return version;
     }

     public void setVersion(int version) {
         this.version = version;
     }

     public String getCat_name() {
         return cat_name;
     }

     public void setCat_name(String cat_name) {
         this.cat_name = cat_name;
     }

     @Embedded
     @AttributeOverrides({
             @AttributeOverride(name = "first_name", column = @Column(name = "first_name")),
             @AttributeOverride(name = "last_name", column = @Column(name = "last_name")) })
     public Name getName() {
         return name;
     }

     public void setName(Name name) {
         this.name = name;
     }
     /*
      * mappedBy属性：
      * 如果关系是单向的，则该关联提供程序确定拥有该关系的字段。
      * 如果关系是双向的，则将关联相反（非拥有）方上的 mappedBy 元素设置为拥
      * 有此关系的字段或属性的名称
      */
     @ManyToMany( fetch = FetchType.EAGER)
     @Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE})
     public Set<Hobby> getHobby() {
         return hobby;
     }

     public void setHobby(Set<Hobby> hobby) {
         this.hobby = hobby;
     }
 }

Hobby.java

 package b11_ManyToMany;
 import java.util.Set;
 import javax.persistence.Entity;
 import javax.persistence.FetchType;
 import javax.persistence.ManyToMany;
 import model.BaseEntity;

 @Entity
 public class Hobby extends BaseEntity {
     /**
      * 实体类
      */
     private static final long serialVersionUID = 4921844599282935594L;

     private String name;
     private Set<Cat> cat;

     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }

     @ManyToMany(fetch=FetchType.LAZY,mappedBy = "hobby")
     public Set<Cat> getCat() {
         return cat;
     }
     public void setCat(Set<Cat> cat) {
         this.cat = cat;
     }
 }

组件类

 package b11_ManyToMany;
 import java.io.Serializable;
 import javax.persistence.Embeddable;

 @Embeddable
 public class Name implements Serializable {
     /**
      * 嵌入式组建
      */
     private static final long serialVersionUID = -2776330321385582872L;

     private String first_name;
     private String last_name;
     public String getFirst_name() {
         return first_name;
     }
     public void setFirst_name(String first_name) {
         this.first_name = first_name;
     }
     public String getLast_name() {
         return last_name;
     }
     public void setLast_name(String last_name) {
         this.last_name = last_name;
     }
 }

Dao

 package daoUtil;
 import org.hibernate.HibernateException;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.Transaction;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.service.ServiceRegistryBuilder;

 public class HibernateUtil {

     private static final SessionFactory sessionFactory;

     static {
         try {
             Configuration cfg = new Configuration().configure();
             ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                     .applySettings(cfg.getProperties()).buildServiceRegistry();
             sessionFactory = cfg.buildSessionFactory(serviceRegistry);
         } catch (Throwable ex) {
             throw new ExceptionInInitializerError(ex);
         }
     }

     public static Session getSession() throws HibernateException {
         return sessionFactory.openSession();
     }

     public static Object save(Object obj){
         Session session = HibernateUtil.getSession();
         Transaction tx = null;
         try {
             tx = session.beginTransaction();
             session.save(obj);
             tx.commit();
         } catch (RuntimeException e) {
             if (tx != null) {
                 tx.rollback();
             }
             throw e;
         } finally {
             session.close();
         }
         return obj;
     }

     public static void delete(Class<?> clazz,String id){
         Session session = HibernateUtil.getSession();
         Transaction tx = null;
         try {
             tx = session.beginTransaction();
             Object obj = session.get(clazz,id);
             session.delete(obj);
             tx.commit();
         } catch (RuntimeException e) {
             if (tx != null) {
                 tx.rollback();
             }
             throw e;
         } finally {
             session.close();
         }
     }
 }

main

 package b11_ManyToMany;
 import java.util.HashSet;
 import java.util.Set;
 import daoUtil.HibernateUtil;

 public class Test_ManyToMany {

     private Cat save(){

         Cat cat1 = new Cat();
         Cat cat2 = new Cat();
         cat1.setCat_name("b11_ManyToMany1");
         cat1.setName(new Name());

         cat2.setCat_name("b11_ManyToMany2");
         cat2.setName(new Name());

         Set<Hobby> hobbies = new HashSet<Hobby>();

         Hobby hobby1 = new Hobby();
         hobby1.setName("足球");
         hobbies.add(hobby1);

         Hobby hobby2 = new Hobby();
         hobby2.setName("篮球");
         hobbies.add(hobby2);

         cat1.setHobby(hobbies);
         cat2.setHobby(hobbies);

         HibernateUtil.save(cat1);
         HibernateUtil.save(cat2);
         System.out.println(cat1.getId());
         System.out.println(cat2.getId());
         return cat1;
     }

     public static void main(String[] args) {
         // 通过cat加载hobby
         Cat cat = new Test_ManyToMany().save();

         Cat cat1 = (Cat)HibernateUtil.getSession().get(Cat.class, cat.getId());
         System.out.println(cat1.getId());

         Set<Hobby> hobbies = cat1.getHobby();
         for (Hobby hobby : hobbies) {
             System.out.println(hobby.getName());
         }
         // delete
 //        HibernateUtil.delete(Cat.class,"402880854c75601d014c75602f9f0000");

         // 通过hobby加载cat
 //        Hobby hobby = (Hobby)HibernateUtil.getSession().get(Hobby.class, "402880854c75601d014c75602fbb0001");
 //        System.out.println(hobby.getId());
 //
 //        Set<Cat> cats = hobby.getCat();
 //        for (Cat cat2 : cats) {
 //            System.out.println(cat2.getCat_name());
 //        }
     }
 }

环境：JDK1.6，MAVEN，tomcat，eclipse

源码地址：http://files.cnblogs.com/files/xiluhua/hibernate%40ManyToMany.rar