JPA嵌入式对象(又名组件)
在实体中可以定义一个嵌入式组件(embedded component), 甚至覆盖该实体中原有的列映射. 组件类必须在类一级定义@Embeddable注解. 在特定的实体的关联属性上使用@Embedded和@AttributeOverride注解可以覆盖该属性对应的嵌入式对象的列映射。
用例代码如下：
- 数据库DDL语句
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
)
- 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="a4_Embeddable.Cat"/> </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
package a4_Embeddable;
import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.Version;
import model.BaseEntity;
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 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;
}
}
组件类
package a4_Embeddable;
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 a4_Embeddable;
import daoUtil.HibernateUtil; public class Test_Embeddable { public static void main(String[] args) { Name name = new Name();
name.setFirst_name("first");
name.setLast_name("last"); Cat cat = new Cat();
cat.setCat_name("Tom");
cat.setName(name); HibernateUtil.save(cat); cat = (Cat)HibernateUtil.getSession().get(Cat.class, cat.getId());
System.out.println(cat.getName().getFirst_name());
}
}
环境：JDK1.6，MAVEN，tomcat，eclipse
源码地址：http://files.cnblogs.com/files/xiluhua/hibernate%40Embeddable.rar