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Hibernate Gossip: 复合主键（二）

可以将主键的信息独立为一个类别，例如：

UserPK.java

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();
    }
}

现在User类别的主键信息被分离出来了，例如：

User.java

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;
    }
}

在映像文件方面，需要指定主键类的信息，例如：

User.hbm.xml

<?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>

在查询数据时，必须指定主键信息，例如：

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();