hibernate复合主键的操作
摘自：http://www.blogjava.net/alex/archive/2006/11/09/80231.html
基于业务需求，您会需要使用两个字段来作复合主键，例如在User数据表中，您也许会使用"name"与"phone"两个字段来定义复合主键。
假设您这么建立User表格：
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
CREATE
TABLE
user
(
name VARCHAR ( 100 ) NOT NULL ,
phone VARCHAR ( 50 ) NOT NULL ,
age INT ,
PRIMARY KEY (name, phone)
);
name VARCHAR ( 100 ) NOT NULL ,
phone VARCHAR ( 50 ) NOT NULL ,
age INT ,
PRIMARY KEY (name, phone)
);
在表格中，"name"与"age"被定义为复合主键，在映像时，您可以让User类别直接带有"name"与"age"这两个属性，而Hibernate要求复合主键类别要实作Serializable接口，并定义equals()与hashCode()方法：
User.java
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
package
onlyfun.caterpillar;
import java.io.Serializable;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
// 复合主键类的对应类别必须实作Serializable接口
public class User implements Serializable {
private String name;
private String phone;
private Integer age;
public User() {
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this .age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this .phone = phone;
}
// 必须重新定义equals()与hashCode()
public boolean equals(Object obj) {
if (obj == this ) {
return true ;
}
if ( ! (obj instanceof User)) {
return false ;
}
User user = (User) obj;
return new EqualsBuilder()
.append( this .name, user.getName())
.append( this .phone, user.getPhone())
.isEquals();
}
public int hashCode() {
return new HashCodeBuilder()
.append( this .name)
.append( this .phone)
.toHashCode();
}
}
import java.io.Serializable;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
// 复合主键类的对应类别必须实作Serializable接口
public class User implements Serializable {
private String name;
private String phone;
private Integer age;
public User() {
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this .age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this .phone = phone;
}
// 必须重新定义equals()与hashCode()
public boolean equals(Object obj) {
if (obj == this ) {
return true ;
}
if ( ! (obj instanceof User)) {
return false ;
}
User user = (User) obj;
return new EqualsBuilder()
.append( this .name, user.getName())
.append( this .phone, user.getPhone())
.isEquals();
}
public int hashCode() {
return new HashCodeBuilder()
.append( this .name)
.append( this .phone)
.toHashCode();
}
}
equals()与hashCode()方法被用作两笔不同数据的识别依据；接着您可以使用<composite-id>在映射文件中定义复合主键与对象的属性对应：
User.hbm.xml
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
<?
xml version="1.0" encoding="utf-8"
?>
<! DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
< hibernate-mapping >
< class name ="onlyfun.caterpillar.User" table ="user" >
< composite-id >
< key-property name ="name"
column ="name"
type ="java.lang.String" />
< key-property name ="phone"
column ="phone"
type ="java.lang.String" />
</ composite-id >
< property name ="age" column ="age" type ="java.lang.Integer" />
</ class >
</ hibernate-mapping >
<! DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
< hibernate-mapping >
< class name ="onlyfun.caterpillar.User" table ="user" >
< composite-id >
< key-property name ="name"
column ="name"
type ="java.lang.String" />
< key-property name ="phone"
column ="phone"
type ="java.lang.String" />
</ composite-id >
< property name ="age" column ="age" type ="java.lang.Integer" />
</ class >
</ hibernate-mapping >
在储存数据方面，复合主键的储存没什么区别，现在的问题在于如何依据复合主键来查询数据，例如使用load()方法，您可以创建一个User实例，并设定复合主键对应的属性，接着再透过load()查询对应的数据，例如：
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
User user
=
new
User();
user.setName( " bush " );
user.setPhone( " 0970123456 " );
Session session = sessionFactory.openSession();
// 以实例设定复合主键并加载对应的数据
user = (User) session.load(User. class , user);
System.out.println(user.getAge() + " \t " +
user.getName() + " \t " +
user.getPhone());
session.close();
user.setName( " bush " );
user.setPhone( " 0970123456 " );
Session session = sessionFactory.openSession();
// 以实例设定复合主键并加载对应的数据
user = (User) session.load(User. class , user);
System.out.println(user.getAge() + " \t " +
user.getName() + " \t " +
user.getPhone());
session.close();
可以将主键的信息独立为一个类别，例如：
UserPK.java
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
package
onlyfun.caterpillar;
import java.io.Serializable;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
public class UserPK implements Serializable {
private String name;
private String phone;
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this .phone = phone;
}
public boolean equals(Object obj) {
if (obj == this ) {
return true ;
}
if ( ! (obj instanceof User)) {
return false ;
}
UserPK pk = (UserPK) obj;
return new EqualsBuilder()
.append( this .name, pk.getName())
.append( this .phone, pk.getPhone())
.isEquals();
}
public int hashCode() {
return new HashCodeBuilder()
.append( this .name)
.append( this .phone)
.toHashCode();
}
}
import java.io.Serializable;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
public class UserPK implements Serializable {
private String name;
private String phone;
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this .phone = phone;
}
public boolean equals(Object obj) {
if (obj == this ) {
return true ;
}
if ( ! (obj instanceof User)) {
return false ;
}
UserPK pk = (UserPK) obj;
return new EqualsBuilder()
.append( this .name, pk.getName())
.append( this .phone, pk.getPhone())
.isEquals();
}
public int hashCode() {
return new HashCodeBuilder()
.append( this .name)
.append( this .phone)
.toHashCode();
}
}
现在User类别的主键信息被分离出来了，例如：
User.java
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
package
onlyfun.caterpillar;
import java.io.Serializable;
public class User implements Serializable {
private UserPK userPK; // 主键
private Integer age;
public User() {
}
public UserPK getUserPK() {
return userPK;
}
public void setUserPK(UserPK userPK) {
this .userPK = userPK;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this .age = age;
}
}
import java.io.Serializable;
public class User implements Serializable {
private UserPK userPK; // 主键
private Integer age;
public User() {
}
public UserPK getUserPK() {
return userPK;
}
public void setUserPK(UserPK userPK) {
this .userPK = userPK;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this .age = age;
}
}
在映像文件方面，需要指定主键类的信息，例如：
User.hbm.xml
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
<?
xml version="1.0" encoding="utf-8"
?>
<! DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
< hibernate-mapping >
< class name ="onlyfun.caterpillar.User" table ="user" >
< composite-id name ="userPK"
class ="onlyfun.caterpillar.UserPK"
unsaved-value ="any" >
< key-property name ="name"
column ="name"
type ="java.lang.String" />
< key-property name ="phone"
column ="phone"
type ="java.lang.String" />
</ composite-id >
< property name ="age" column ="age" type ="java.lang.Integer" />
</ class >
</ hibernate-mapping >
<! DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
< hibernate-mapping >
< class name ="onlyfun.caterpillar.User" table ="user" >
< composite-id name ="userPK"
class ="onlyfun.caterpillar.UserPK"
unsaved-value ="any" >
< key-property name ="name"
column ="name"
type ="java.lang.String" />
< key-property name ="phone"
column ="phone"
type ="java.lang.String" />
</ composite-id >
< property name ="age" column ="age" type ="java.lang.Integer" />
</ class >
</ hibernate-mapping >
在查询数据时，必须指定主键信息，例如：
<!--<br><br>Code highlighting produced by Actipro CodeHighlighter (freeware)<br>http://www.CodeHighlighter.com/<br><br>-->
UserPK pk
=
new
UserPK();
pk.setName( " bush " );
pk.setPhone( " 0970123456 " );
Session session = sessionFactory.openSession();
// 以主键类实例设定复合主键并加载对应的数据
User user = (User) session.load(User. class , pk);
System.out.println(user.getAge() + " \t " +
user.getUserPK().getName() + " \t " +
user.getUserPK().getPhone());
session.close();
pk.setName( " bush " );
pk.setPhone( " 0970123456 " );
Session session = sessionFactory.openSession();
// 以主键类实例设定复合主键并加载对应的数据
User user = (User) session.load(User. class , pk);
System.out.println(user.getAge() + " \t " +
user.getUserPK().getName() + " \t " +
user.getUserPK().getPhone());
session.close();