hibernate多映射 数据无法查询

Question

班级类

package hibernate;

import java.io.Serializable;

import java.util.HashSet;

import java.util.Set;

public class Grade implements Serializable {

private int gid;

private String sname;

private String gdesc;

private Set<student1> students=new HashSet<student1>();

public Grade(int gid, String sname, String gdesc, Set<student1> students) {

super();

this.gid = gid;

this.sname = sname;

this.gdesc = gdesc;

this.students = students;

}

public Grade() {

super();

}

public int getGid() {

return gid;

}

public void setGid(int gid) {

this.gid = gid;

}

public String getSname() {

return sname;

}

public void setSname(String sname) {

this.sname = sname;

}

public String getGdesc() {

return gdesc;

}

public void setGdesc(String gdesc) {

this.gdesc = gdesc;

}

public Set<student1> getStudents() {

return students;

}

public void setStudents(Set<student1> students) {

this.students = students;

}

public Grade(String sname, String gdesc) {

super();

this.sname = sname;

this.gdesc = gdesc;

}

}

学生类

package hibernate;

import java.io.Serializable;

public class student1 implements Serializable{

private int sid;

private String sname;

private String sex;

public int getSid() {

return sid;

}

public void setSid(int sid) {

this.sid = sid;

}

public String getSname() {

return sname;

}

public void setSname(String sname) {

this.sname = sname;

}

public String getSex() {

return sex;

}

public void setSex(String sex) {

this.sex = sex;

}

public student1(String sname, String sex) {

super();

this.sname = sname;

this.sex = sex;

}

}

班级hbm类

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!-- Generated 2017-3-25 22:16:53 by Hibernate Tools 3.5.0.Final -->

<hibernate-mapping>

    <class name="hibernate.Grade" table="grade1">

        <id name="gid" type="int">

            <column name="GID" />

            <generator class="increment" />

        </id>

        <property name="sname" type="java.lang.String">

            <column name="SNAME" />

        </property>

        <property name="gdesc" type="java.lang.String">

            <column name="GDESC" />

        </property>

        <set name="students" table="student1" inverse="false" lazy="true">

            <key>

                <column name="gid" />

            </key>

            <one-to-many class="hibernate.student1" />

        </set>

    </class>

</hibernate-mapping>

  学生hbm

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!-- Generated 2017-3-25 22:16:53 by Hibernate Tools 3.5.0.Final -->

<hibernate-mapping>

    <class name="hibernate.student1" table="student1">

        <id name="sid" type="int">

            <column name="SID" />

            <generator class="increment" />

        </id>

        <property name="sname" type="java.lang.String">

            <column name="SNAME" />

        </property>

        <property name="sex" type="java.lang.String">

            <column name="SEX" />

        </property>

    </class>

</hibernate-mapping>

配置文档

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-configuration PUBLIC

"-//Hibernate/Hibernate Configuration DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

    <property name="connection.username">root</property>

    <property name="connection.password">123456</property>

    <property name="connection.driver_name">com.mysql.jdbc.Driver</property>

    <property name="connection.url">jdbc:mysql://localhost:3306/student3?useUnicode=true&amp;characterEncoding=UTF-8</property>

     <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect </property> 

     

     <property name="show_sql">true</property>

     <property name="format_sql">true</property>

     <property name="hbm2ddl.auto">create</property>

    <mapping resource="student1.hbm.xml"/>

     <mapping resource="Grade.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

测试类

package hibernate;

import java.util.Date;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

import org.hibernate.cfg.Configuration;

import org.hibernate.service.ServiceRegistry;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

public class StudentsTest {

  private SessionFactory sessionFactory;

  private Session session;

  private Transaction transaction;

@Before

public void init(){

//创建配置对象

Configuration config=new Configuration().configure();

config.addClass(Grade.class);

config.addClass(student1.class);

//创建服务注册对象

ServiceRegistry serviceRegistry =new StandardServiceRegistryBuilder().applySettings(config.getProperties()).build();

//创建会话工厂对象

sessionFactory=config.buildSessionFactory(serviceRegistry);

//会话对象

session=sessionFactory.openSession();

//开启事物

transaction=session.beginTransaction();

}

@After

public void destroy(){

transaction.commit();

transaction.commit();//提交事物

session.close();//关闭会话

sessionFactory.close();//关闭会话工厂

}

@Test

public void testSaveStudent(){

Grade g=new Grade("java二班","java软件开发一班");

student1 stu1=new student1("王五","男");

student1 stu2=new student1("赵六","男");

g.getStudents().add(stu1);

g.getStudents().add(stu2);

session.save(g);

session.save(stu1);

session.save(stu2);

}

@Test

public void testsearchGrade(){

Grade grade=(Grade)session.get(Grade.class, 1);

System.out.println(grade);

}

只要测试 testsearchGrade() 方法 数据表就会把以前的数据清空