Hibernate Gossip: 複合主鍵（二）

来源：互联网发布：德云色淘宝店网址编辑：程序博客网时间：2024/04/28 21:57

可以將主鍵的資訊獨立為一個類別，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();
 }
}

現在User類別的主鍵資訊被分離出來了，例如：

User.java

package onlyfun.caterpillar;

import java.io.Serializable;

public class User implements Serializable {
    private UserPK userPK; // 主鍵
    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;
    }
}

在映射文件方面，需要指定主鍵類的資訊，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>

在查詢資料時，必須指定主鍵資訊，例如：

UserPK pk = new UserPK();
pk.setName("bush");
pk.setPhone("0970123456");

Session session = sessionFactory.openSession();
// 以主鍵類實例設定複合主鍵並載入對應的資料
User user = (User) session.load(User.class, pk);

System.out.println(user.getAge() + "/t" +
                          user.getUserPK().getName() + "/t" +
                          user.getUserPK().getPhone());
session.close();