hibernate映射文件中的id标签以及联合主键

hibernate映射文件中的id标签以及联合主键

一、id标签

       被映射的类必须定义对应数据库表主键字段。大多数类有一个JavaBeans风格的属性， 为每一个实例包含唯一的标识。<id> 元素定义了该属性到数据库表主键字段的映射

 

二、联合场景

学生表Student是由id和name联合形成主键

三、联合主键类的编写

      1）实现java.io.Serializable接口

      2）必须重写equals() 和 hashCode() 方法

 

package com.linys.model;

/**
 * StudentId entity. @author MyEclipse Persistence Tools
 */

public class StudentId implements java.io.Serializable {

	// Fields

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private Integer id;
	private String name;

	// Constructors

	/** default constructor */
	public StudentId() {
	}

	/** full constructor */
	public StudentId(Integer id, String name) {
		this.id = id;
		this.name = name;
	}

	// Property accessors

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public boolean equals(Object other) {
		if ((this == other))
			return true;
		if ((other == null))
			return false;
		if (!(other instanceof StudentId))
			return false;
		StudentId castOther = (StudentId) other;

		return ((this.getId() == castOther.getId()) || (this.getId() != null
				&& castOther.getId() != null && this.getId().equals(
				castOther.getId())))
				&& ((this.getName() == castOther.getName()) || (this.getName() != null
						&& castOther.getName() != null && this.getName()
						.equals(castOther.getName())));
	}

	public int hashCode() {
		int result = 17;

		result = 37 * result + (getId() == null ? 0 : this.getId().hashCode());
		result = 37 * result
				+ (getName() == null ? 0 : this.getName().hashCode());
		return result;
	}

}

三、学生类的编写

 

package com.linys.model;

/**
 * Student entity. @author MyEclipse Persistence Tools
 */

public class Student implements java.io.Serializable {

	// Fields

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private StudentId id;
	private Integer age;

	// Constructors

	/** default constructor */
	public Student() {
	}

	/** minimal constructor */
	public Student(StudentId id) {
		this.id = id;
	}

	/** full constructor */
	public Student(StudentId id, Integer age) {
		this.id = id;
		this.age = age;
	}

	// Property accessors

	public StudentId getId() {
		return this.id;
	}

	public void setId(StudentId id) {
		this.id = id;
	}

	public Integer getAge() {
		return this.age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}

}

 

四、映射文件

Student.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">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="com.linys.model.Student" table="student">
        <composite-id name="id" class="com.linys.model.StudentId">
            <key-property name="id" type="java.lang.Integer">
                <column name="id" />
                
            </key-property>
            <key-property name="name" type="java.lang.String">
                <column name="name" length="50" />
            </key-property>
        </composite-id>
        <property name="age" type="java.lang.Integer">
            <column name="age" />
        </property>
    </class>
</hibernate-mapping>

 

其中：

<composite-id 指定联合主键的信息

 <key-property 指定在StudentId类中的联合信息

五、测试类

 

 

package com.linys.model;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

public class TestUniPk {

	static SessionFactory sf;

	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
		sf = new Configuration().configure().buildSessionFactory();

	}

	@Test
	public void testUniPk(){
		StudentId stuId=new StudentId();
		//stuId.setId(1);
		stuId.setName("linys");
		
		Student stu=new Student();
		stu.setAge(23);
		stu.setId(stuId);
		
		Session session =sf.openSession();
		Transaction tr=session.beginTransaction();
		session.save(stu);
		tr.commit();
		session.save(stu);
		
		
	}
	@AfterClass
	public static void tearDownAfterClass() throws Exception {
		sf.close();
	}

}