Hibernate学习4—关联关系一对多映射

package com.cy.model;

public class Student {
    private long id;
    private String name;
    private Class c;
    
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    
    public Class getC() {
        return c;
    }
    public void setC(Class c) {
        this.c = c;
    }
    
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + "]";
    }
    
    
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.cy.model">
    <class name="Student" table="t_student">
        <id name="id" column="stuId">
            <generator class="identity"></generator>
        </id>
        <property name="name" column="stuName"></property>
        <!-- 
            属性名是c；
            表的外键的列名是classId，关联类com.cy.model.Class
         -->
        <many-to-one name="c" column="classId" class="com.cy.model.Class"></many-to-one>
    </class>
</hibernate-mapping>

package com.cy.service;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

public class StudentTest2 {

    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
        System.out.println("类初始化前调用...");
    }

    @AfterClass
    public static void tearDownAfterClass() throws Exception {
        System.out.println("类初始化后调用...");
    }

    @Before
    public void setUp() throws Exception {
        System.out.println("测试方法前调用...");
    }

    @After
    public void tearDown() throws Exception {
        System.out.println("测试方法后调用...");
    }

    @Test
    public void test() {
        System.out.println("测试方法...");
    }
    
    
    /*
     *  打印如下：
           类初始化前调用...
        测试方法前调用...
        测试方法...
        测试方法后调用...
        类初始化后调用...
     */
}

package com.cy.service;


import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.cy.model.Class;
import com.cy.model.Student;
import com.cy.util.HibernateUtil;

public class StudentTest3 {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession();    
        session.beginTransaction();    
    }

    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit();    
        session.close();    
    }

    @Test
    public void testSaveClassAndStudentWithCascade() {
        Class c = new Class();    //临时对象,还没有被持久化
        c.setName("08计本");
        
        Student s1 = new Student();
        s1.setName("张三");
        s1.setC(c);
        Student s2 = new Student();
        s2.setName("李四");
        s2.setC(c);
        
        session.save(s1);    //(cascade为none) student持久化对象引用了一个临时对象，保存抛出异常，保存失败。
        session.save(s2);
    }

}

<hibernate-mapping package="com.cy.model">
    <class name="Student" table="t_student">
        <id name="id" column="stuId">
            <generator class="identity"></generator>
        </id>
        <property name="name" column="stuName"></property>
        <!-- 
            属性名是c；
            表的外键的列名是classId，关联类com.cy.model.Class
         -->
        <many-to-one name="c" column="classId" class="com.cy.model.Class" cascade="save-update"></many-to-one>
    </class>
</hibernate-mapping>