hibernate 多对一
业务逻辑：
Teacher类和Student类，假定为多对一的关系。
1. 数据库schema
Teachers表:
create table TEACHERS
(
ID NUMBER(10) not null,
TEACHERNAME VARCHAR2(15)
)
alter table TEACHERS
add constraint DERE primary key (ID)
Students表：
create table STUDENTS
(
ID NUMBER(10) not null,
STUDENTNAME VARCHAR2(15),
TEACHER_ID NUMBER(10)
)
alter table STUDENTS
add constraint RERE primary key (ID)
alter table STUDENTS
add constraint FFF foreign key (TEACHER_ID)
references TEACHERS (ID);
2. Teacher.Java和Student.java
Teacher.java
package mypack;
public class Teacher {
//教师id
private Long id;
//教师名称
private String teacherName;
/**
* 缺省构造函数
*/
public Teacher() {
}
/**
* 得到教师id
* @return Long 教师id
*/
public Long getId() {
return id;
}
/**
* 设置教师id
* @param id Long 教师id
*/
public void setId(Long id) {
this.id = id;
}
/**
* 得到教师名称
* @return String 教师名称
*/
public String getTeacherName() {
return teacherName;
}
/**
* 设置教师名称
* @param teacherName String 教师名称
*/
public void setTeacherName(String teacherName) {
this.teacherName = teacherName;
}
/**
* 构造函数
* @param teacherName String
*/
public Teacher(String teacherName) {
this.teacherName = teacherName;
}
}
Student.java
package mypack;
public class Student {
//学生id
private Long id;
//学生名称
private String studentName;
//教师类
private Teacher teacher;
/**
* 缺省构造函数
*/
public Student() {
}
/**
* 得到学生id
* @return Long 学生id
*/
public Long getId() {
return id;
}
/**
* 设置学生id
* @param id Long 学生id
*/
public void setId(Long id) {
this.id = id;
}
/**
* 得到学生名称
* @return String 学生名称
*/
public String getStudentName() {
return studentName;
}
/**
* 设置学生名称
* @param studentName String 学生名称
*/
public void setStudentName(String studentName) {
this.studentName = studentName;
}
/**
* 得到教师对象
* @return Teacher 教师对象
*/
public Teacher getTeacher() {
return teacher;
}
/**
* 设置教师对象
* @param teacher Teacher 教师对象
*/
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
/**
* 构造函数
* @param string String
* @param teacher Teacher
*/
public Student(String studentName, Teacher teacher) {
this.studentName = studentName;
this.teacher = teacher;
}
}
3. hibernate.properties
## Oracle
hibernate.dialect net.sf.hibernate.dialect.Oracle9Dialect
hibernate.dialect net.sf.hibernate.dialect.OracleDialect
hibernate.connection.driver_class oracle.jdbc.driver.OracleDriver
hibernate.connection.username jbcm
hibernate.connection.passWord jbcm
hibernate.connection.url jdbc:oracle:thin:@localhost:1521:wsy
4. Teacher.hbm.xml和Student.hbm.xml
Teacher.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping >
<class name="mypack.Teacher" table="teachers" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="teacherName" type="string" >
<column name="teacherName" length="15" />
</property>
</class>
</hibernate-mapping>
Student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping >
<class name="mypack.Student" table="students" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="studentName" type="string" >
<column name="studentName" length="15" />
</property>
<many-to-one
name="teacher"
column="teacher_id"
class="mypack.Teacher"
cascade="save-update"
/>
</class>
</hibernate-mapping>
5. 数据库操作类
BusinessService.java
package mypack;
import net.sf.hibernate.*;
import net.sf.hibernate.cfg.Configuration;
import java.util.*;
public class BusinessService{
//session工厂类
public static SessionFactory sessionFactory;
//实始化session工厂
static{
try{
//建立配置类，添加Student类和Teacher类
Configuration config = new Configuration();
config.addClass(Student.class)
.addClass(Teacher.class);
//得到sessionFactory对象
sessionFactory = config.buildSessionFactory();
}catch(Exception e){e.printStackTrace();}
}
/**
* 通过学生类，查找教师类
* @param student Student
* @throws Exception
* @return List
*/
public List findTeacherByStudent(Student student) throws Exception{
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
List orders=(List)session.find("from Student as o where o.teacher.id="+student.getId());
tx.commit();
return orders;
}catch (Exception e) {
if (tx != null) {
tx.rollback();
}
throw e;
} finally {
session.close();
}
}
/**
* 查找指定id的学生类
* @param student_id long
* @throws Exception
* @return Student
*/
public Student findStudent(long student_id) throws Exception{
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
Student student=(Student)session.load(Student.class,new Long(student_id));
tx.commit();
return student;
}catch (Exception e) {
if (tx != null) {
//发生错误，回滚
tx.rollback();
}
throw e;
} finally {
//没有错误，关闭session
session.close();
}
}
/**
* 级连保存Teacher对象和Student对象
* @throws Exception
*/
public void saveTeacherAndStudentWithCascade() throws Exception{
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
Teacher teacher=new Teacher("myTeacher");
Student student1=new Student("student1",teacher);
Student student2=new Student("student2",teacher);
session.save(student1);
session.save(student2);
tx.commit();
}catch (Exception e) {
if (tx != null) {
//发生错误，回滚
tx.rollback();
}
e.printStackTrace();
} finally {
// 没有错误，关闭session
session.close();
}
}
/**
* 保存教师和学生对象
* @throws Exception
*/
public void saveTeacherAndStudent() throws Exception{
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
Teacher teacher=new Teacher("teacher1");
session.save(teacher);
Student student1=new Student("student001",teacher);
Student student2=new Student("student002",teacher);
session.save(student1);
session.save(student2);
//提交事务
tx.commit();
}catch (Exception e) {
if (tx != null) {
//发生错误，回滚
tx.rollback();
}
throw e;
} finally {
// 没有错误，关闭session
session.close();
}
}
/**
* 输出学生对象集合
* @param students List
*/
public void printStudents(List students){
for (Iterator it = students.iterator(); it.hasNext();) {
Student student=(Student)it.next();
System.out.println("OrderNumber of "+student.getTeacher().getTeacherName()+ " :"+student.getStudentName());
}
}
/**
* 测试方法
* @throws Exception
*/
public void test() throws Exception{
saveTeacherAndStudent();
// saveTeacherAndStudentWithCascade();
// Student student=findStudent(1);
// List students=findTeacherByStudent(student);
// printStudents(students);
}
public static void main(String args[]) throws Exception {
new BusinessService().test();
sessionFactory.close();
}
}
目录结构示意：
Classes
Hibernate.property
/mypack
Teacher.java
Student.java
BusinessService.java
Teacher.hbm.xml
Student.hbm.xml
参考资料：精通Hibernate:Java对象持久化技术详解 孙卫琴
