Hibernate，JPA注解@Entity

通过@Entity注解将一个类声明为一个实体bean(即一个持久化POJO类), @Id注解则声明了该实体bean的标识属性. 其他的映射定义是隐式的.

就是说一个持久化POJO类，除了主键ID需要@Id显示注解，其他列都可以不做任何注解。

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)

 )

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="a1_Entity.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 a1_Entity;

 import javax.persistence.Entity;

 import model.BaseEntity;

 @Entity

 public class Cat extends BaseEntity{

     /**

      * 实体类

      */

     private static final long serialVersionUID = -2776330321385582872L;

     private String cat_name;

     public String getCat_name() {

         return cat_name;

     }

     public void setCat_name(String cat_name) {

         this.cat_name = cat_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) {

             // Log exception!

             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 a1_Entity;

 import daoUtil.HibernateUtil;

 public class Test_Entity {

     public static void main(String[] args) {

         Cat cat = new Cat();

         cat.setId("1");

         cat.setCat_name("test1@Entity");

         HibernateUtil.save(cat);

     }

 }

环境：JDK1.6，MAVEN

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

巴特西

Hibernate，JPA注解@Entity

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