Hibernate，JPA注解@DynamicInsert和@DynamicUpdate，Hibernate如何插入sysdate

@DynamicInsert属性:设置为true,设置为true,表示insert对象的时候,生成动态的insert语句,如果这个字段的值是null就不会加入到insert语句当中.默认false。

比如希望数据库插入日期或时间戳字段时，在对象字段为空的情况下，表字段能自动填写当前的sysdate。

@DynamicUpdate属性:设置为true,设置为true,表示update对象的时候,生成动态的update语句,如果这个字段的值是null就不会被加入到update语句中,默认false。

比如只想更新某个属性，但是却把整个对象的属性都更新了，这并不是我们希望的结果，我们希望的结果是：我更改了哪些字段，只要更新我修改的字段就够了。

 

@DynamicInsert

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) default sysdate,
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="a2_DynamicInsert_Update.Cat"/>
19         
20     </session-factory>
21 </hibernate-configuration>

• java类

实体类 - 基类 

1 package model;
 2 
 3 import java.io.Serializable;
 4 import java.util.Date;
 5 import javax.persistence.Column;
 6 import javax.persistence.GeneratedValue;
 7 import javax.persistence.Id;
 8 import javax.persistence.MappedSuperclass;
 9 import org.hibernate.annotations.GenericGenerator;
10 
11 /**
12  * 实体类 - 基类
13  */
14 @MappedSuperclass
15 public class BaseEntity implements Serializable {
16 
17     private static final long serialVersionUID = -6718838800112233445L;
18 
19     private String id;// ID
20     private Date create_time;// 创建日期
21     private Date update_time;// 修改日期
22     @Id
23     @Column(length = 32, nullable = true)
24     @GeneratedValue(generator = "uuid")
25     @GenericGenerator(name = "uuid", strategy = "uuid")
26     public String getId() {
27         return id;
28     }
29 
30     public void setId(String id) {
31         this.id = id;
32     }
33 
34     @Column(updatable = false)
35     public Date getCreate_time() {
36         return create_time;
37     }
40     public void setCreate_time(Date create_time) {
41         this.create_time = create_time;
42     }
43 
44     public Date getUpdate_time() {
45         return update_time;
46     }
47 
48     public void setUpdate_time(Date update_time) {
49         this.update_time = update_time;
50     }
51 
52     @Override
53     public int hashCode() {
54         return id == null ? System.identityHashCode(this) : id.hashCode();
55     }
56 
58     @Override
59     public boolean equals(Object obj) {
60         if (this == obj) {
61             return true;
62         }
63         if (obj == null) {
64             return false;
65         }
66         if (getClass().getPackage() != obj.getClass().getPackage()) {
67             return false;
68         }
69         final BaseEntity other = (BaseEntity) obj;
70         if (id == null) {
71             if (other.getId() != null) {
72                 return false;
73             }
74         } else if (!id.equals(other.getId())) {
75             return false;
76         }
77         return true;
78     }
79 }

实体类

1 package a2_DynamicInsert_Update;
 2 import javax.persistence.Entity;
 3 import model.BaseEntity;
 4 import org.hibernate.annotations.DynamicInsert;
 5 import org.hibernate.annotations.DynamicUpdate;
 6 
 7 @Entity
 8 @DynamicInsert
 9 @DynamicUpdate
10 public class Cat extends BaseEntity{
11     /**
12      * 实体类
13      */
14     private static final long serialVersionUID = -2776330321385582872L;
15     
16     private String cat_name;
17 
18     public String getCat_name() {
19         return cat_name;
20     }
21 
22     public void setCat_name(String cat_name) {
23         this.cat_name = cat_name;
24     }
25 }

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 a2_DynamicInsert_Update;
 2 import a2_DynamicInsert_Update.Cat;
 3 import daoUtil.HibernateUtil;
 4 
 5 public class Test_DynamicInsert {
 6 
 7     public static void main(String[] args) {
 8         Cat cat = new Cat();
 9         cat.setCat_name("test2@DynamicInsert");
10         HibernateUtil.save(cat);
11     }
12 }

@DynamicInsert注解下Hibernate日志打印SQL：

Hibernate: insert into Cat (cat_name, id) values (?, ?)

反之

Hibernate: insert into Cat (create_time, update_time, cat_name, id) values (?, ?, ?, ?)

 

@DynamicUpdate

写了个main程序测试：代码如下：

• 数据库DML语句：

insert into CAT (ID, CAT_NAME, CREATE_TIME, UPDATE_TIME)
values ('8a6cc5a34c456829014c45682a860000', 'test@555', SYSDATE, SYSDATE);

• hibernate.cfg.xml 同上
• java类

实体类,Dao 同上。

main

1 package a2_DynamicInsert_Update;
 2 import org.hibernate.Session;
 3 import org.hibernate.Transaction;
 4 import daoUtil.HibernateUtil;
 5 
 6 public class Test_DynamicUpdate {
 7 
 8     public static void main(String[] args) {
 9         Session session = HibernateUtil.getSession();
10         Transaction tx = null;
11         try {
12             tx = session.beginTransaction();
13             Cat cat = (Cat)session.get(Cat.class, "8a6cc5a34c6e7f32014c6e7f33500000");
14             cat.setCat_name("test@DynamicUpdate");
15             tx.commit();
16         } catch (RuntimeException e) {
17             if (tx != null) {
18                 tx.rollback();
19             }
20             throw e;
21         } finally {
22             session.close();
23         }
24         
25     }
26 }

Cat实体类@DynamicUpdate注解下Hibernate日志打印SQL：

说明：如果字段有更新，Hibernate才会对该字段进行更新

Hibernate: update Cat set update_time=? where id=?

反之Cat实体类去掉@DynamicUpdate

说明：不管字段有没有更新，Hibernate都会对该字段进行更新

Hibernate: update Cat set update_time=?, cat_name=? where id=?

 

Hibernate在执行更新操作前，会比对一下当前Session上下文中的对象与需要更新的对象数据是否一致，也就是说会确认数据有没有变化，没变化的话，无论写多少次session.update(cat)，都不会执行更新操作。