Hibernat之关系的处理多对多

第一步：编写两个pojo，比如一个学生表一个课程表  这里使用注解。

需要

课程表:

package com.qcf.pox;

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

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;

@Entity
public class Course {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    @ManyToMany(mappedBy="courses")
    private Set<Student2> student2s=new HashSet<Student2>();
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Student2> getStudent2s() {
        return student2s;
    }
    public void setStudent2s(Set<Student2> student2s) {
        this.student2s = student2s;
    }
    public Course(int id, String name, Set<Student2> student2s) {
        super();
        this.id = id;
        this.name = name;
        this.student2s = student2s;
    }
    public Course() {
        super();
    }
    
}

 

学生表：

 

package com.qcf.pox;

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

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;

@Entity
public class Student2 {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    @ManyToMany(cascade=CascadeType.ALL)
    private Set<Course> courses=new HashSet<Course>();
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Course> getCourses() {
        return courses;
    }
    public void addCourses(Course courses) {
        this.courses.add(courses);
    }
    public Student2(int id, String name, Set<Course> courses) {
        super();
        this.id = id;
        this.name = name;
        this.courses = courses;
    }
    public Student2() {
        super();
    }
    
}

 

 

第二步：在hibernate.cfg.xml文件中引入这两个po类

 

        <mapping class="com.qcf.pox.Student2"/>
        <mapping class="com.qcf.pox.Course"/>

 

 

 

第三步：编写测试代码

 

package com.qcf.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;

import com.qcf.pox.Course;
import com.qcf.pox.Student2;

public class TestManyToMany {
    public static void main(String[] args) {
        Configuration configuration=new AnnotationConfiguration().configure();
        SessionFactory factory=configuration.buildSessionFactory();
        Session session=factory.openSession();
        Transaction transaction=session.beginTransaction();
        
        //创建两个课程
        Course course=new Course();
        course.setName("java");
        Course course2=new Course();
        course2.setName("C#");
        
        //创建两个学生
        Student2 student=new Student2();
        student.setName("zhangsan");
        Student2 student2=new Student2();
        student2.setName("lisi");
        
        student.addCourses(course);
        student.addCourses(course2);
        
        student2.addCourses(course);
        student2.addCourses(course2);
        
        session.save(student);
        session.save(student2);
        
        transaction.commit();
        session.close();
        
    }

}

 

执行成功后的结果：