Hibernate,JPA注解@ManyToMany
@ManyToMany默认值,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
1 create table CAT 2 ( 3 id VARCHAR2(32 CHAR) not null, 4 create_time TIMESTAMP(6), 5 update_time TIMESTAMP(6), 6 cat_name VARCHAR2(255 CHAR), 7 first_name VARCHAR2(255 CHAR), 8 last_name VARCHAR2(255 CHAR), 9 version NUMBER(10) not null 10 )
2,HOBBY表
1 create table HOBBY 2 ( 3 id VARCHAR2(32 CHAR) not null, 4 create_time TIMESTAMP(6), 5 update_time TIMESTAMP(6), 6 name VARCHAR2(255 CHAR), 7 cat_id VARCHAR2(32 CHAR) 8 )
- hibernate.cfg.xml
1 <?xml version="1.0" encoding="utf-8" ?> 2 <!DOCTYPE hibernate-configuration 3 PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" 4 "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 5 <hibernate-configuration> 6 <session-factory> 7 <!-- 数据库驱动配置 --> 8 <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property> 9 <property name="connection.driver_class">oracle.jdbc.OracleDriver</property> 10 <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property> 11 <property name="connection.username">wxuatuser</property> 12 <property name="connection.password">xlh</property> 13 <property name="show_sql">true</property> 14 <!-- 自动执行DDL属性是update,不是true --> 15 <property name="hbm2ddl.auto">update</property> 16 <!-- hibernate实体类 --> 17 18 <mapping class="b11_ManyToMany.Cat"/> 19 <mapping class="b11_ManyToMany.Hobby"/> 20 21 </session-factory> 22 </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
1 package b11_ManyToMany; 2 3 import java.util.Set; 4 import javax.persistence.AttributeOverride; 5 import javax.persistence.AttributeOverrides; 6 import javax.persistence.Column; 7 import javax.persistence.Embedded; 8 import javax.persistence.Entity; 9 import javax.persistence.FetchType; 10 import javax.persistence.ManyToMany; 11 import javax.persistence.Version; 12 import model.BaseEntity; 13 import org.hibernate.annotations.Cascade; 14 import org.hibernate.annotations.DynamicInsert; 15 import org.hibernate.annotations.DynamicUpdate; 16 17 @Entity 18 @DynamicInsert 19 @DynamicUpdate 20 public class Cat extends BaseEntity{ 21 /** 22 * 实体类 23 */ 24 private static final long serialVersionUID = -2776330321385582872L; 25 26 private Set<Hobby> hobby; 27 private String cat_name; 28 private Name name; 29 private int version; 30 31 @Version 32 public int getVersion() { 33 return version; 34 } 35 36 public void setVersion(int version) { 37 this.version = version; 38 } 39 40 public String getCat_name() { 41 return cat_name; 42 } 43 44 public void setCat_name(String cat_name) { 45 this.cat_name = cat_name; 46 } 47 48 @Embedded 49 @AttributeOverrides({ 50 @AttributeOverride(name = "first_name", column = @Column(name = "first_name")), 51 @AttributeOverride(name = "last_name", column = @Column(name = "last_name")) }) 52 public Name getName() { 53 return name; 54 } 55 56 public void setName(Name name) { 57 this.name = name; 58 } 59 /* 60 * mappedBy属性: 61 * 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。 62 * 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 63 * 有此关系的字段或属性的名称 64 */ 65 @ManyToMany( fetch = FetchType.EAGER) 66 @Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE}) 67 public Set<Hobby> getHobby() { 68 return hobby; 69 } 70 71 public void setHobby(Set<Hobby> hobby) { 72 this.hobby = hobby; 73 } 74 }
Hobby.java
1 package b11_ManyToMany; 2 import java.util.Set; 3 import javax.persistence.Entity; 4 import javax.persistence.FetchType; 5 import javax.persistence.ManyToMany; 6 import model.BaseEntity; 7 8 @Entity 9 public class Hobby extends BaseEntity { 10 /** 11 * 实体类 12 */ 13 private static final long serialVersionUID = 4921844599282935594L; 14 15 private String name; 16 private Set<Cat> cat; 17 18 public String getName() { 19 return name; 20 } 21 public void setName(String name) { 22 this.name = name; 23 } 24 25 @ManyToMany(fetch=FetchType.LAZY,mappedBy = "hobby") 26 public Set<Cat> getCat() { 27 return cat; 28 } 29 public void setCat(Set<Cat> cat) { 30 this.cat = cat; 31 } 32 }
组件类
1 package b11_ManyToMany; 2 import java.io.Serializable; 3 import javax.persistence.Embeddable; 4 5 @Embeddable 6 public class Name implements Serializable { 7 /** 8 * 嵌入式组建 9 */ 10 private static final long serialVersionUID = -2776330321385582872L; 11 12 private String first_name; 13 private String last_name; 14 public String getFirst_name() { 15 return first_name; 16 } 17 public void setFirst_name(String first_name) { 18 this.first_name = first_name; 19 } 20 public String getLast_name() { 21 return last_name; 22 } 23 public void setLast_name(String last_name) { 24 this.last_name = last_name; 25 } 26 }
Dao
1 package daoUtil; 2 import org.hibernate.HibernateException; 3 import org.hibernate.Session; 4 import org.hibernate.SessionFactory; 5 import org.hibernate.Transaction; 6 import org.hibernate.cfg.Configuration; 7 import org.hibernate.service.ServiceRegistry; 8 import org.hibernate.service.ServiceRegistryBuilder; 9 10 public class HibernateUtil { 11 12 private static final SessionFactory sessionFactory; 13 14 static { 15 try { 16 Configuration cfg = new Configuration().configure(); 17 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder() 18 .applySettings(cfg.getProperties()).buildServiceRegistry(); 19 sessionFactory = cfg.buildSessionFactory(serviceRegistry); 20 } catch (Throwable ex) { 21 throw new ExceptionInInitializerError(ex); 22 } 23 } 24 25 public static Session getSession() throws HibernateException { 26 return sessionFactory.openSession(); 27 } 28 29 public static Object save(Object obj){ 30 Session session = HibernateUtil.getSession(); 31 Transaction tx = null; 32 try { 33 tx = session.beginTransaction(); 34 session.save(obj); 35 tx.commit(); 36 } catch (RuntimeException e) { 37 if (tx != null) { 38 tx.rollback(); 39 } 40 throw e; 41 } finally { 42 session.close(); 43 } 44 return obj; 45 } 46 47 public static void delete(Class<?> clazz,String id){ 48 Session session = HibernateUtil.getSession(); 49 Transaction tx = null; 50 try { 51 tx = session.beginTransaction(); 52 Object obj = session.get(clazz,id); 53 session.delete(obj); 54 tx.commit(); 55 } catch (RuntimeException e) { 56 if (tx != null) { 57 tx.rollback(); 58 } 59 throw e; 60 } finally { 61 session.close(); 62 } 63 } 64 }
main
1 package b11_ManyToMany; 2 import java.util.HashSet; 3 import java.util.Set; 4 import daoUtil.HibernateUtil; 5 6 public class Test_ManyToMany { 7 8 private Cat save(){ 9 10 Cat cat1 = new Cat(); 11 Cat cat2 = new Cat(); 12 cat1.setCat_name("b11_ManyToMany1"); 13 cat1.setName(new Name()); 14 15 cat2.setCat_name("b11_ManyToMany2"); 16 cat2.setName(new Name()); 17 18 Set<Hobby> hobbies = new HashSet<Hobby>(); 19 20 Hobby hobby1 = new Hobby(); 21 hobby1.setName("足球"); 22 hobbies.add(hobby1); 23 24 Hobby hobby2 = new Hobby(); 25 hobby2.setName("篮球"); 26 hobbies.add(hobby2); 27 28 cat1.setHobby(hobbies); 29 cat2.setHobby(hobbies); 30 31 HibernateUtil.save(cat1); 32 HibernateUtil.save(cat2); 33 System.out.println(cat1.getId()); 34 System.out.println(cat2.getId()); 35 return cat1; 36 } 37 38 public static void main(String[] args) { 39 // 通过cat加载hobby 40 Cat cat = new Test_ManyToMany().save(); 41 42 Cat cat1 = (Cat)HibernateUtil.getSession().get(Cat.class, cat.getId()); 43 System.out.println(cat1.getId()); 44 45 Set<Hobby> hobbies = cat1.getHobby(); 46 for (Hobby hobby : hobbies) { 47 System.out.println(hobby.getName()); 48 } 49 // delete 50 // HibernateUtil.delete(Cat.class,"402880854c75601d014c75602f9f0000"); 51 52 // 通过hobby加载cat 53 // Hobby hobby = (Hobby)HibernateUtil.getSession().get(Hobby.class, "402880854c75601d014c75602fbb0001"); 54 // System.out.println(hobby.getId()); 55 // 56 // Set<Cat> cats = hobby.getCat(); 57 // for (Cat cat2 : cats) { 58 // System.out.println(cat2.getCat_name()); 59 // } 60 } 61 }
环境:JDK1.6,MAVEN,tomcat,eclipse
源码地址:http://files.cnblogs.com/files/xiluhua/hibernate%40ManyToMany.rar
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