心得6-hibernate级联之多对多单双向剖析

多对多: 学生与课程,以下主要从案例出发，由案例具体解析

单向多对多
Student.hbm.xml

<?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.hbsi.many2many">

    <class name="Student" table="student">
        <id name="id">
           <generator class="native"/>
        </id>
        <property name="name" column="name"/>
        
        <set name="course" table="student_course" cascade="save-update">
          <key column="student_id"/>
          <many-to-many column="course_id" class="Course" />
        </set>
    </class>
    
</hibernate-mapping>

Course.hbm.xml

<?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.hbsi.many2many">
  
    <class name="Course" table="course">
        <id name="id">
           <generator class="native"/>
        </id>
        <property name="name" column="name"/>

    </class>
</hibernate-mapping>

测试类
package com.hbsi.many2many;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.junit.Test;

import com.hbsi.utils.HibernateSessionFactory;

public class TestApp {
	
	Session session = HibernateSessionFactory.getSession();
	@Test
	public void add(){
		
		session.beginTransaction();
		
		Student student1 = new Student();
		student1.setName("keven");
		
		Student student2 = new Student();
		student2.setName("jie");
		
		Course course1 = new Course();
		course1.setName("english");
		
		Course course2 = new Course();
		course2.setName("chinese");
		
		Set<Course> courses = new HashSet<Course>();
		courses.add(course1);
		courses.add(course2);
		
		student1.setCourse(courses);
		
		session.save(student1);
		session.save(student2);
		session.save(course1);
		session.save(course2);
		
		session.getTransaction().commit();
		HibernateSessionFactory.closeSession();
		
	}

	@Test
	public void find(){
		Student student = (Student) session.get(Student.class,1);
		Set<Course> courses = student.getCourse();
		for(Course course : courses){
			System.out.println(student.getName()+"---"+course.getName());
		}
	}
}


双向多对多
Student.hbm.xml

<?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.hbsi.many2manyboth">

    <class name="Student" table="studentboth">
        <id name="id">
           <generator class="native"/>
        </id>
        <property name="name" column="name"/>
        
        <set name="course" table="student_courseboth" cascade="save-update">
          <key column="student_id"/>
          <many-to-many column="course_id" class="Course" />
        </set>
    </class>
    
</hibernate-mapping>

Course.hbm.xml
 
<?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.hbsi.many2manyboth">
  
    <class name="Course" table="courseboth">
        <id name="id">
           <generator class="native"/>
        </id>
        <property name="name" column="name"/>

	<set name="student" table="student_courseboth" cascade="save-update">
	  <key column="course_id"/>
	  <many-to-many class="Student" column="student_id"/>
	</set>
    </class>
</hibernate-mapping>

测试类

package com.hbsi.many2manyboth;

import java.util.HashSet;
import java.util.Set;
import org.hibernate.Session;
import org.junit.Test;
import com.hbsi.utils.HibernateSessionFactory;

public class TestApp {
	
	Session session = HibernateSessionFactory.getSession();
	@Test
	public void add(){
		
		session.beginTransaction();
		
		Student student1 = new Student();
		student1.setName("keven");
		
		Student student2 = new Student();
		student2.setName("jie");
		
		Course course1 = new Course();
		course1.setName("english");
		
		Course course2 = new Course();
		course2.setName("chinese");		
		
		/*达到的添加功能一样，可以从多方的任何一方添加
		 * Set<Course> courses = new HashSet<Course>();
		courses.add(course1);
		courses.add(course2);
		
		student1.setCourse(courses);
		student2.setCourse(courses);*/
		
		Set<Student> students = new HashSet<Student>();
		students.add(student1);
		students.add(student2);
		
		course1.setStudent(students);
		course2.setStudent(students);
		
		session.save(student1);
		session.save(student2);
		session.save(course1);
		session.save(course2);
		
		session.getTransaction().commit();
		HibernateSessionFactory.closeSession();
		
	}
	@Test
	public void find(){
		Student student = (Student) session.get(Student.class,1);
		Set<Course> courses = student.getCourse();
		for(Course course : courses){
			System.out.println(student.getName()+"---"+course.getName());
		}
		Course course1 = (Course) session.get(Course.class,1);
		Set<Student> students = course1.getStudent();
		for(Student student1 : students){
			System.out.println(course1.getName()+"---"+student1.getName());
		}
	}

}