Hibernate注解@Entity

浏览数：48 / 时间：2015年06月09日

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。

写了个main程序测试：代码如下：

数据库DDL语句：

1 create table CAT
2 (
3   id          VARCHAR2(32) not null,
4   CAT_NAME    VARCHAR2(32),
5   create_time DATE,
6   update_time DATE
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 
 6 <hibernate-configuration>
 7     <session-factory>
 8         <!-- 数据库驱动配置 -->
 9         <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
10         <property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
11         <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>
12         <property name="connection.username">wxuatuser</property>
13         <property name="connection.password">xlh</property>
14         <property name="show_sql">true</property>
15         
16         <!-- hibernate实体类 -->
17         <mapping class="test1.Cat"/>
18     </session-factory>
19 </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 test1;
 2 
 3 import javax.persistence.Entity;
 4 import model.BaseEntity;
 5 /**
 6  * 实体类
 7  */
 8 @Entity
 9 public class Cat extends BaseEntity{
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 
23 }

main入口

 1 package test1;
 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 import test1.Cat;
11 
12 public class HibernateUtil {
13 
14     private static final SessionFactory sessionFactory;
15 
16     static {
17         try {
18             Configuration cfg = new Configuration().configure();
19             ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
20                     .applySettings(cfg.getProperties()).buildServiceRegistry();
21             sessionFactory = cfg.buildSessionFactory(serviceRegistry);
22         } catch (Throwable ex) {
23             // Log exception!
24             throw new ExceptionInInitializerError(ex);
25         }
26     }
27 
28     public static Session getSession() throws HibernateException {
29         return sessionFactory.openSession();
30     }
31 
32     public static void main(String[] args) {
33         Session session = HibernateUtil.getSession();
34         Transaction tx = null;
35         try {
36             tx = session.beginTransaction();
37             Cat cat = new Cat();
38             cat.setCat_name("cat5");
39             session.save(cat);
40             tx.commit();
41         } catch (RuntimeException e) {
42             if (tx != null) {
43                 tx.rollback();
44             }
45             throw e;
46         } finally {
47             session.close();
48         }
49 
50     }
51 }