Hibernate(三)一对多关系

Hibernate(三)一对多关系（源码）

 

链接：http://pan.baidu.com/s/1o8k04NS 密码：0eht

 

 

 

1.所依赖的包

 

2.建表语句

create table grade
(
gid int primary key,
gname varchar(20) not null,
gdesc varchar(50)
);
create table student
(
sid int primary key,
sname varchar(20) not null,
sex char(2),
gid int
);
alter table student add constraint fk_student_gid foreign key (gid)
references grade(gid);

 

3.配置文件Hibernate.cfg.xml

<!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="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
<property name="hibernate.connection.url"> jdbc:mysql://localhost:3306/hibernate</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>

<!-- 指定映射文件的路径 -->
<mapping resource="com/imooc/entity/Grade.hbm.xml" />
<mapping resource="com/imooc/entity/Student.hbm.xml" />
</session-factory>
</hibernate-configuration>

 

4.工具类

package com.imooc.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
private static SessionFactory sessionFactory;
private static Session session;

static {
// 创建Configuration对象，读取hibernate.cfg.xml文件，完成初始化
Configuration config = new Configuration().configure();
StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder()
.applySettings(config.getProperties());
StandardServiceRegistry ssr=ssrb.build();
sessionFactory=config.buildSessionFactory(ssr);
}

//获取SessionFactory
public static SessionFactory getSessionFactory(){
return sessionFactory;
}

//获取Session
public static Session getSession(){
session=sessionFactory.openSession();
return session;
}

//关闭Session
public static void closeSession(Session session){
if(session!=null){
session.close();
}
}
}

 

5.班级类Grade.java

package com.imooc.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Grade implements Serializable {
private int gid;
private String gname;
private String gdesc;
private Set<Student> students=new HashSet<Student>();

public int getGid() {
return gid;
}

public void setGid(int gid) {
this.gid = gid;
}

public String getGname() {
return gname;
}

public void setGname(String gname) {
this.gname = gname;
}

public String getGdesc() {
return gdesc;
}

public void setGdesc(String gdesc) {
this.gdesc = gdesc;
}

public Grade() {
super();
}

public Set<Student> getStudents() {
return students;
}

public void setStudents(Set<Student> students) {
this.students = students;
}

public Grade(int gid, String gname, String gdesc) {
super();
this.gid = gid;
this.gname = gname;
this.gdesc = gdesc;
}

public Grade(String gname, String gdesc) {
super();
this.gname = gname;
this.gdesc = gdesc;
}

}

 

6.班级映射文件Grade.hbm.xml

<?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>
<class name="com.imooc.entity.Grade" table="grade">
<id name="gid" column="gid" type="java.lang.Integer">
<generator class="increment"></generator>
</id>
<property name="gname" type="java.lang.String">
<column name="gname" length="20" not-null="true"></column>
</property>
<property name="gdesc">
<column name="gdesc"></column>
</property>
<!-- 配置一对多关联关系 设置inverse属性为true 由多方维护关联关系-->
<set name="students" table="student" inverse="true" cascade="save-update">
<key column="gid"></key>
<one-to-many class="com.imooc.entity.Student"/>
</set>
</class>
</hibernate-mapping>

 

7.student.java类

package com.imooc.entity;

import java.io.Serializable;

public class Student implements Serializable {
private int sid;
private String sname;
private String sex;
// 在多方定义一个一方的引用
private Grade grade;

public Student(String sname, String sex) {
super();
this.sname = sname;

this.sex = sex;
}

public Grade getGrade() {
return grade;
}
public void setGrade(Grade grade) {
this.grade = grade;
}

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 Student() {
super();
}

}

 

8.student.hbm.xml映射

<?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>
<class name="com.imooc.entity.Student" table="student">
<id name="sid" column="sid" type="java.lang.Integer">
<generator class="increment"></generator>
</id>
<property name="sname" type="java.lang.String">
<column name="sname" length="20" not-null="true"></column>
</property>
<property name="sex">
<column name="sex"></column>
</property>
<!-- 配置多对一关联关系 -->
<many-to-one name="grade" class="com.imooc.entity.Grade" column="gid" cascade="all"></many-to-one>
</class>
</hibernate-mapping>

 

9测试类

package com.imooc.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.imooc.entity.Grade;
import com.imooc.entity.Student;
import com.imooc.util.HibernateUtil;

/*
* 单向一对多关系关系（班级--->学生）
* 建立关联关系后，可以方便的从一个对象导航到另一个对象
* 注意关联的方向
*/
public class Test {
private static Student stu1;
private static Student stu2;

public static void main(String[] args) {
add();
// findStudentsByGrade();
// update();
// delete();

}

// 将学生添加到班级
public static void add() {
Grade g = new Grade("Java一班", "Java软件开发一班");
stu1 = new Student("张三", "男");
stu2 = new Student("穆女神", "女");

// 如果希望在学生表中添加对应的班级编号，需要在班级中添加学生，建立关联关系
g.getStudents().add(stu1);
g.getStudents().add(stu2);

Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
session.save(g);
session.save(stu1);
session.save(stu2);
tx.commit();
HibernateUtil.closeSession(session);
}

// 查询班级中包含的学生
public static void findStudentsByGrade() {
Session session = HibernateUtil.getSession();
Grade grade = (Grade) session.get(Grade.class, 1);
System.out.println(grade.getGname() + "," + grade.getGdesc());

/*
* Set<Student> students=grade.getStudents(); for(Student stu:students){
* System.out.println(stu.getSname()+","+stu.getSex()); }
*/
}

// 修改学生信息
public static void update() {
Grade g = new Grade("Java二班", "Java软件开发二班");

Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
Student stu = (Student) session.get(Student.class, 1);
// g.getStudents().add(stu);
session.save(g);
tx.commit();
HibernateUtil.closeSession(session);
}

// 删除学生信息
public static void delete() {
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
Student stu = (Student) session.get(Student.class, 2);
session.delete(stu);
tx.commit();
HibernateUtil.closeSession(session);
}
}

 

10测试类2

package com.imooc.test;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.imooc.entity.Grade;
import com.imooc.entity.Student;
import com.imooc.util.HibernateUtil;

/*
* 单向多对一（学生--->班级）
*/
public class Test02 {
public static void main(String[] args) {
// save();
findGradeByStudent();
}

//保存
public static void save(){
Grade g=new Grade("Java一班","Java软件开发一班");
Student stu1=new Student("慕女神", "女");
Student stu2=new Student("小慕慕", "男");

//设置关联关系inverse
g.getStudents().add(stu1);
g.getStudents().add(stu2);
stu1.setGrade(g);
stu2.setGrade(g);

Session session=HibernateUtil.getSession();
Transaction tx=session.beginTransaction();
session.save(g);//级联操作
// session.save(stu1);
// session.save(stu2);
tx.commit();
HibernateUtil.closeSession(session);
}

//查询
public static void findGradeByStudent(){
Session session = HibernateUtil.getSession();
Student str=(Student) session.get(Student.class,2);
System.out.println(str.getSid()+""+str.getSname()+""+str.getSex());

//获取学生所在班级信息
Grade grade = str.getGrade();
System.out.println(grade.getGid()+""+grade.getGname()+""+grade.getGdesc());
HibernateUtil.closeSession(session);
}
}