hibernate中java.util.Date类型映射

秒速五厘米 2021-09-12 04:14 237阅读 0赞

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在Hibernate中对于java.util.Date类型的映射为：

<table> 
 <tbody> 
  <tr> 
   <td>java类型</td> 
   <td>Hibernate类型</td> 
   <td>Mysql类型</td> 
  </tr> 
  <tr> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      java.util.Date、java.sql.Date 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      date 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      DATE 
    </div> </td> 
  </tr> 
  <tr> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      java.util.Date、java.sql.Time 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      time 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      TIME 
    </div> </td> 
  </tr> 
  <tr> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      java.util.Date、java.sql.Timestamp 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      timestamp 
    </div> </td> 
   <td style="padding-bottom:0cm; padding-left:0cm; padding-right:0cm; padding-top:0cm"> 
    <div>
      TIMESTAMP 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

![Image 1][]

如果使用timestamp作为Date类型映射时，具体代码如下：

Java代码

1.  public class User \{   
2.      private String userPK;   
3.      private String userID;   
4.      private String password;   
5.      private String nickname;   
6.      private boolean state;   
7.      private boolean role;   
8.      private Date registerDate;   
9.      private int points;   
10.     public String getUserPK() \{   
11.         return userPK;   
12.     \}   
13.     private void setUserPK(String userPK) \{   
14.         this.userPK = userPK;   
15.     \}   
16.     public String getUserID() \{   
17.         return userID;   
18.     \}   
19.     public void setUserID(String userID) \{   
20.         this.userID = userID;   
21.     \}   
22.     public String getPassword() \{   
23.         return password;   
24.     \}   
25.     public void setPassword(String password) \{   
26.         this.password = password;   
27.     \}   
28.     public String getNickname() \{   
29.         return nickname;   
30.     \}   
31.     public void setNickname(String nickname) \{   
32.         this.nickname = nickname;   
33.     \}   
34.     public Date getRegisterDate() \{   
35.         return registerDate;   
36.     \}   
37.     public void setRegisterDate(Date registerDate) \{   
38.         this.registerDate = registerDate;   
39.     \}   
40.     public int getPoints() \{   
41.         return points;   
42.     \}   
43.     public void setPoints(int points) \{   
44.         this.points = points;   
45.     \}   
46.     public void setState(boolean state) \{   
47.         this.state = state;   
48.     \}   
49.     public boolean getState()\{   
50.         return this.state;   
51.     \}   
52.     public void setRole(boolean role) \{   
53.         this.role = role;   
54.     \}   
55.     public boolean getRole()\{   
56.         return this.role;   
57.     \}   
58. \}

public class User {
    	private String userPK;
    	private String userID;
    	private String password;
    	private String nickname;
    	private boolean state;
    	private boolean role;
    	private Date registerDate;
    	private int points;
    	public String getUserPK() {
    		return userPK;
    	}
    	private void setUserPK(String userPK) {
    		this.userPK = userPK;
    	}
    	public String getUserID() {
    		return userID;
    	}
    	public void setUserID(String userID) {
    		this.userID = userID;
    	}
    	public String getPassword() {
    		return password;
    	}
    	public void setPassword(String password) {
    		this.password = password;
    	}
    	public String getNickname() {
    		return nickname;
    	}
    	public void setNickname(String nickname) {
    		this.nickname = nickname;
    	}
    	public Date getRegisterDate() {
    		return registerDate;
    	}
    	public void setRegisterDate(Date registerDate) {
    		this.registerDate = registerDate;
    	}
    	public int getPoints() {
    		return points;
    	}
    	public void setPoints(int points) {
    		this.points = points;
    	}
    	public void setState(boolean state) {
    		this.state = state;
    	}
    	public boolean getState(){
    		return this.state;
    	}
    	public void setRole(boolean role) {
    		this.role = role;
    	}
    	public boolean getRole(){
    		return this.role;
    	}
    }

映射代码：

Xml代码

1.  <?xml version="1.0"?>  
2.  <!DOCTYPE hibernate-mapping PUBLIC   
3.      "-//Hibernate/Hibernate Mapping DTD 3.0//EN"   
4.      "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">  
5.  <hibernate-mapping package="org.brucefeng.sinter.domain">  
6.    <class name="User" table="sinter\_user">  
7.      <id name="userPK" column="userpk" unsaved-value="null">  
8.          <generator class="uuid.hex"></generator>  
9.      </id>  
10.     <property name="userID" type="string" column="userid" unique="true"></property>  
11.     <property name="password" type="string" column="password"></property>  
12.     <property name="nickname" type="string" column="name"></property>  
13.     <property name="state" type="boolean" column="state"></property>  
14.     <property name="role" type="boolean" column="role"></property>  
15.     <property name="points" type="integer" column="points"></property>  
16.     <property name="registerDate" type="timestamp" column="registerdate"></property>  
17.   </class>  
18. </hibernate-mapping>

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
    	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    <hibernate-mapping package="org.brucefeng.sinter.domain">
      <class name="User" table="sinter_user">
      	<id name="userPK" column="userpk" unsaved-value="null">
      		<generator class="uuid.hex"></generator>
      	</id>
      	<property name="userID" type="string" column="userid" unique="true"></property>
      	<property name="password" type="string" column="password"></property>
      	<property name="nickname" type="string" column="name"></property>
      	<property name="state" type="boolean" column="state"></property>
      	<property name="role" type="boolean" column="role"></property>
      	<property name="points" type="integer" column="points"></property>
      	<property name="registerDate" type="timestamp" column="registerdate"></property>
      </class>
    </hibernate-mapping>

Java代码

1.  User testUser = new User();   
2.    
3.  testUser.setRegisterDate(new Date);   
4.    
5.  session.save(testUser);

User testUser = new User();
    
    testUser.setRegisterDate(new Date);
    
    session.save(testUser);

存储结束之后，由数据库中重新查询出此对象：

Java代码

1.  User savedUser = session.load(User.class,id);

User savedUser = session.load(User.class,id);

而此时

testUser.getRegisterDate.equals(savedUser.getRegisterDate)返回值为false;

此时可发现test.getRegisterDate().class为java.util.Date，savedUser.getRegisterDate().class为java.sql.Timestamp。查看java的文档可知

java doc 写道

The Timestamp.equals(Object) method never returns true when passed an object that isn't an instance of java.sql.Timestamp, because the nanos component of a date is unknown. As a result, the Timestamp.equals(Object) method is not symmetric with respect to the java.util.Date.equals(Object) method.

也就是说Timestamp和Date类型并不能进行相等比较的。当然在程序中比较两个时间点的相等性是不切合实际的，但如果一些特殊应用需要比较的话，可以使用其他方法解决。例如：

Java代码

1.  public void setRegisterDate(Date registerDate) \{   
2.          this.registerDate = new Date(registerDate.getTime());   
3.      \}

public void setRegisterDate(Date registerDate) {
    		this.registerDate = new Date(registerDate.getTime());
    	}

这样即可顺利转变类型及值了。但是Hibernate中并没有对java.util.Date类型进行很好的映射，个人也觉得可以不采用Date类型记录时间，可适当考虑Calendar类型。

[Image 1]: