hibernate学习五之one-to-many双向关联

hibernate学习5之one-to-many双向关联
一对多双向关联映射：
* 在一一端的集合上使用<key>，在对方表中加入一个外键指向一一端
* 在多一端采用<many-to-one>

<!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><property name="hibernate.connection.url">jdbc:mysql://localhost/hibernate_one2many_1</property><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password">bjsxt</property><property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property><property name="hibernate.show_sql">true</property><mapping resource="com/bjsxt/hibernate/Classes.hbm.xml"/><mapping resource="com/bjsxt/hibernate/Student.hbm.xml"/></session-factory></hibernate-configuration>

public class Student {private int id;private String name;private Classes classes;//多对一，多个学生对应一个班级//setter，getter}

import java.util.Set;public class Classes {private int id;private String name;private Set students; //一对多//setter，getter}

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.bjsxt.hibernate.Student" table="t_student"><id name="id"><generator column="classesid"/></class></hibernate-mapping>

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.bjsxt.hibernate"><class name="Classes" table="t_classes"><id name="id"><generator inverse="true" cascade="all"><key column="classesid"/><one-to-many name="code">import java.util.HashSet;import java.util.Iterator;import java.util.Set;import junit.framework.TestCase;import org.hibernate.Session;public class One2ManyTest extends TestCase {public void testSave1() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Student student1 = new Student();student1.setName("10");session.save(student1);Student student2 = new Student();student2.setName("祖儿");session.save(student2);Set students = new HashSet();students.add(student1);students.add(student2);Classes classes = new Classes();classes.setName("尚学堂");classes.setStudents(students);//可以正确保存session.save(classes);session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}public void testSave2() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Classes classes = new Classes();classes.setName("尚学堂");session.save(classes);Student student1 = new Student();student1.setName("10");student1.setClasses(classes);session.save(student1);Student student2 = new Student();student2.setName("祖儿");student2.setClasses(classes);session.save(student2);session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}public void testSave3() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Classes classes = new Classes();classes.setName("尚学堂");Student student1 = new Student();student1.setName("10");student1.setClasses(classes);Student student2 = new Student();student2.setName("祖儿");student2.setClasses(classes);Set students = new HashSet();students.add(student1);students.add(student2);classes.setStudents(students);//可以正确保存session.save(classes);session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}public void testLoad1() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Classes classes = (Classes)session.load(Classes.class, 1);System.out.println("classes.name=" + classes.getName());Set students = classes.getStudents();for (Iterator iter=students.iterator(); iter.hasNext();) {Student student = (Student)iter.next();System.out.println("student.name=" + student.getName());}session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}public void testLoad2() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Student student = (Student)session.load(Student.class, 1);System.out.println("student.name=" + student.getName());System.out.println("student.classes.name=" + student.getClasses().getName());session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}}