学步园

参考：http://hi.baidu.com/ohaozy/blog/item/ed486a33bc83cf48ac4b5f75.html

下面是我调试过的代码

1. 建类

Teacher.java

package com.sjtu.xw.pojo;<br /> import java.util.HashSet;<br /> import java.util.Set;<br /> public class Teacher {<br /> private long id;<br /> private String teaName;<br /> private Set students = new HashSet();<br /> public long getId() {<br /> return id;<br /> }<br /> public void setId(long id) {<br /> this.id = id;<br /> }<br /> public String getTeaName() {<br /> return teaName;<br /> }<br /> public void setTeaName(String teaName) {<br /> this.teaName = teaName;<br /> }</p> <p> public Set getStudents() {<br /> return students;<br /> }<br /> public void setStudents(Set students) {<br /> this.students = students;<br /> }<br /> public String toString() {<br /> return "Teacher:[teacherId=" + this.id + "/tteacherName="<br /> + this.teaName + "]";<br /> }<br /> }<br />  

Student.java

package com.sjtu.xw.pojo;<br /> public class Student {<br /> private long id;<br /> private String stuName;<br /> public long getId() {<br /> return id;<br /> }<br /> public void setId(long id) {<br /> this.id = id;<br /> }<br /> public String getStuName() {<br /> return stuName;<br /> }<br /> public void setStuName(String stuName) {<br /> this.stuName = stuName;<br /> }<br /> public String toString() {<br /> return "student:[studentId=" + this.id + "/tstudentName="<br /> + this.stuName + "]";<br /> }<br /> }<br />  

Student.hbm.xml

<?xml version="1.0"?><br /> <!DOCTYPE hibernate-mapping PUBLIC<br /> "-//Hibernate/Hibernate Mapping DTD 3.0//EN"<br /> "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><br /> <hibernate-mapping package="com.sjtu.xw.pojo"><br /> <class name="Student" table="student"><br /> <id name="id" column="id"><br /> <generator class="native"></generator><br /> </id><br /> <property name="stuName" column="studentName" length="30" /><br /> </class><br /> </hibernate-mapping> 

Teacher.hbm.xml

<?xml version="1.0"?><br /> <!DOCTYPE hibernate-mapping PUBLIC<br /> "-//Hibernate/Hibernate Mapping DTD 3.0//EN"<br /> "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><br /> <hibernate-mapping package="com.sjtu.xw.pojo"><br /> <class name="Teacher" table="teacher"><br /> <id name="id" column="id"><br /> <generator class="native"></generator><br /> </id><br /> <property name="teaName" column="teacherName" length="30" /></p> <p> <set name="students" fetch="join" lazy="false"><br /> <!--<br /> <set name="students"><br /> --><br /> <key column="teacherId"></key><br /> <!--<br /> 这里的column="teacherId" 是指明了在student表里有一个teacherId的列名，是指向teacher表的外键<br /> --><br /> <one-to-many class="Student" /><br /> </set><br /> </class><br /> </hibernate-mapping> 

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?><br /> <!DOCTYPE hibernate-configuration PUBLIC<br /> "-//Hibernate/Hibernate Configuration DTD 3.0//EN"<br /> "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><br /> <hibernate-configuration><br /> <session-factory><br /> <!-- Database connection settings --><br /> <property name="connection.driver_class">com.mysql.jdbc.Driver</property><br /> <property name="connection.url">jdbc:mysql://localhost:3306/coursems</property><br /> <property name="connection.username">root</property><br /> <property name="connection.password">root</property><br /> <property name="dialect">org.hibernate.dialect.MySQLDialect</property><br /> <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property><br /> <property name="show_sql">false</property><br /> <mapping resource="com/sjtu/xw/pojo/Student.hbm.xml"/><br /> <mapping resource="com/sjtu/xw/pojo/Teacher.hbm.xml"/><br /> </session-factory><br /> </hibernate-configuration> 

HibernateUtil.java

package com.sjtu.xw.util;</p> <p>import org.hibernate.SessionFactory;<br /> import org.hibernate.cfg.Configuration;<br /> public class HibernateUtil {<br /> private static final SessionFactory sessionFactory = buildSessionFactory();<br /> private static SessionFactory buildSessionFactory() {<br /> try {<br /> // Create the SessionFactory from hibernate.cfg.xml<br /> return new Configuration().configure().buildSessionFactory();<br /> }<br /> catch (Throwable ex) {<br /> // Make sure you log the exception, as it might be swallowed<br /> System.err.println("Initial SessionFactory creation failed." + ex);<br /> throw new ExceptionInInitializerError(ex);<br /> }<br /> }<br /> public static SessionFactory getSessionFactory() {<br /> return sessionFactory;<br /> }<br /> } 

Test.java

package com.sjtu.xw.test;<br /> import java.util.List;<br /> import org.hibernate.Session;<br /> import org.hibernate.SessionFactory;<br /> import org.hibernate.Transaction;<br /> import com.sjtu.xw.pojo.Student;<br /> import com.sjtu.xw.pojo.Teacher;<br /> import com.sjtu.xw.util.HibernateUtil;<br /> public class Test {<br /> public static void main(String[] args)<br /> {<br /> Test test=new Test();<br /> //test.addStudent();<br /> //test.addTeacher();<br /> test.test();<br /> }<br /> public void addStudent() {<br /> Student student = new Student();<br /> student.setStuName("student6");<br /> SessionFactory sf = HibernateUtil.getSessionFactory();<br /> Session session = sf.openSession();<br /> Transaction tx = session.beginTransaction();<br /> session.save(student);<br /> tx.commit();<br /> session.close();<br /> sf.close();<br /> }<br /> public void addTeacher() {<br /> Student student = new Student();<br /> student.setId(3);<br /> Teacher teacher = new Teacher();<br /> teacher.setTeaName("Teacher1");<br /> teacher.getStudents().add(student); // 把id为1的学生添加到教师对象<br /> // 保存这个教师的同时会更新student表<br /> SessionFactory sf = HibernateUtil.getSessionFactory();<br /> Session session = sf.openSession();<br /> Transaction tx = session.beginTransaction();<br /> session.save(teacher);<br /> tx.commit();<br /> session.close();<br /> sf.close();<br /> }<br /> public void test()<br /> {<br /> SessionFactory sf = HibernateUtil.getSessionFactory();<br /> Session session = sf.openSession();<br /> Transaction tx = session.beginTransaction();</p> <p> List list = session.createQuery("from Teacher t where t.id=1").list();<br /> //List list = session.createQuery("from Teacher t left join fetch t.students where t.id=1").list();</p> <p> Teacher t = (Teacher)list.get(0);</p> <p> System.out.println(t);//<br /> System.out.println(t.getStudents().iterator().next());<br /> for(int i=0;i<list.size();i++)<br /> {<br /> Teacher tt = (Teacher)list.get(i);<br /> System.out.println(tt);//<br /> System.out.println(tt.getStudents().iterator().next());<br /> }</p> <p> /*//未明白什么意思，和session有什么关系呢？<br /> * 上面这句话放在session结束前,student在用到的时候将会自动被查询出来，否则查询语句应改为:<br /> * from Teacher t left join fetch t.students where t.id=1<br /> * 或者设置teacher.hbm.xml里的set属性，加上：fetch="join" lazy="false":<br /> * <set name="students" fetch="join" lazy="false"><br /> * <key column="teacherId"></key> <one-to-many class="model.Student"/> </set><br /> */<br /> tx.commit();<br /> session.close();<br /> sf.close();<br /> }<br /> }