Hibernate，JPA注解@Entity

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mb5fe948249bc3d 2015-03-23 14:41:00

文章标签 hibernate JPA注解 java 实体类 oracle 文章分类 代码人生

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：

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 )

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="a1_Entity.Cat"/>
19         
20     </session-factory>
21 </hibernate-configuration>

java类

实体类 - 基类

1 package model;
 2 import java.io.Serializable;
 3 import java.util.Date;
 4 import javax.persistence.Column;
 5 import javax.persistence.GeneratedValue;
 6 import javax.persistence.Id;
 7 import javax.persistence.MappedSuperclass;
 8 import org.hibernate.annotations.GenericGenerator;
 9 
10 /**
11  * 实体类 - 基类
12  */
13 @MappedSuperclass
14 public class BaseEntity implements Serializable {
15 
16     private static final long serialVersionUID = -6718838800112233445L;
17 
18     private String id;// ID
19     private Date create_time;// 创建日期
20     private Date update_time;// 修改日期
21     @Id
22     @Column(length = 32, nullable = true)
23     @GeneratedValue(generator = "uuid")
24     @GenericGenerator(name = "uuid", strategy = "uuid")
25     public String getId() {
26         return id;
27     }
28     public void setId(String id) {
29         this.id = id;
30     }
31     @Column(updatable = false)
32     public Date getCreate_time() {
33         return create_time;
34     }
35     public void setCreate_time(Date create_time) {
36         this.create_time = create_time;
37     }
38     public Date getUpdate_time() {
39         return update_time;
40     }
41     public void setUpdate_time(Date update_time) {
42         this.update_time = update_time;
43     }
44     @Override
45     public int hashCode() {
46         return id == null ? System.identityHashCode(this) : id.hashCode();
47     }
48     @Override
49     public boolean equals(Object obj) {
50         if (this == obj) {
51             return true;
52         }
53         if (obj == null) {
54             return false;
55         }
56         if (getClass().getPackage() != obj.getClass().getPackage()) {
57             return false;
58         }
59         final BaseEntity other = (BaseEntity) obj;
60         if (id == null) {
61             if (other.getId() != null) {
62                 return false;
63             }
64         } else if (!id.equals(other.getId())) {
65             return false;
66         }
67         return true;
68     }
69 }

实体类

1 package a1_Entity;
 2 import javax.persistence.Entity;
 3 
 4 import model.BaseEntity;
 5 
 6 @Entity
 7 public class Cat extends BaseEntity{
 8     /**
 9      * 实体类
10      */
11     private static final long serialVersionUID = -2776330321385582872L;
12     
13     private String cat_name;
14 
15     public String getCat_name() {
16         return cat_name;
17     }
18 
19     public void setCat_name(String cat_name) {
20         this.cat_name = cat_name;
21     }
22 }

Dao

1 package daoUtil;
 2 
 3 import org.hibernate.HibernateException;
 4 import org.hibernate.Session;
 5 import org.hibernate.SessionFactory;
 6 import org.hibernate.Transaction;
 7 import org.hibernate.cfg.Configuration;
 8 import org.hibernate.service.ServiceRegistry;
 9 import org.hibernate.service.ServiceRegistryBuilder;
10 
11 public class HibernateUtil {
12 
13     private static final SessionFactory sessionFactory;
14 
15     static {
16         try {
17             Configuration cfg = new Configuration().configure();
18             ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
19                     .applySettings(cfg.getProperties()).buildServiceRegistry();
20             sessionFactory = cfg.buildSessionFactory(serviceRegistry);
21         } catch (Throwable ex) {
22             // Log exception!
23             throw new ExceptionInInitializerError(ex);
24         }
25     }
26 
27     public static Session getSession() throws HibernateException {
28         return sessionFactory.openSession();
29     }
30 
31     public static Object save(Object obj){
32         Session session = HibernateUtil.getSession();
33         Transaction tx = null;
34         try {
35             tx = session.beginTransaction();
36             session.save(obj);
37             tx.commit();
38         } catch (RuntimeException e) {
39             if (tx != null) {
40                 tx.rollback();
41             }
42             throw e;
43         } finally {
44             session.close();
45         }
46         return obj;
47     }
48     
49     public static void delete(Class<?> clazz,String id){
50         Session session = HibernateUtil.getSession();
51         Transaction tx = null;
52         try {
53             tx = session.beginTransaction();
54             Object obj = session.get(clazz,id);
55             session.delete(obj);
56             tx.commit();
57         } catch (RuntimeException e) {
58             if (tx != null) {
59                 tx.rollback();
60             }
61             throw e;
62         } finally {
63             session.close();
64         }
65     }
66 }

main

1 package a1_Entity;
 2 
 3 import daoUtil.HibernateUtil;
 4 
 5 public class Test_Entity {
 6 
 7     public static void main(String[] args) {
 8         Cat cat = new Cat();
 9         cat.setId("1");
10         cat.setCat_name("test1@Entity");
11         HibernateUtil.save(cat);
12     }
13 }