hibernate多對多（ManyToMany）注解開發

hibernate多對多注解開發小Demo。上代碼

Student.java

package com.it.hibernate.domain;

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

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
@Entity
@Table(name="c_student")
public class Student {
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	@Id
	//@Column(name="s_id")
	private Integer id;
	@Column(name="s_name")
	private String name;
	@ManyToMany(targetEntity=Teacher.class)
	// 使用JoinTabl來描述中間表，并描述中間表中外鍵與Student,Teacher的映射關系
	// joinColumns它是用來描述Student與中間表中的映射關系
	// inverseJoinColums它是用來描述Teacher與中間表中的映射關系
	@JoinTable(name="s_t",
	joinColumns={@JoinColumn(name="c_s_id",referencedColumnName="id")},
	inverseJoinColumns={@JoinColumn(name="c_t_id",referencedColumnName="id")}
			)
	private Set<Teacher> t = new HashSet<Teacher>();
	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Student(Integer id, String name, Set<Teacher> t) {
		super();
		this.id = id;
		this.name = name;
		this.t = t;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Set<Teacher> getT() {
		return t;
	}
	public void setT(Set<Teacher> t) {
		this.t = t;
	}
	
	

}
           

Teacher.java

package com.it.hibernate.domain;

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

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;
import org.hibernate.annotations.GenericGenerator;
@Entity
@Table(name="c_teacher")
public class Teacher {
	@Id
	@GenericGenerator(name="myuuid",strategy="uuid")
	@GeneratedValue(generator="myuuid") //引入自定義主鍵生成政策
	//@Column(name="t_id")
	private String id;
	@Column(name="t_name")
	private String name;
	@ManyToMany(targetEntity=Student.class,mappedBy="t") //讓student維護外鍵表
	@Cascade(CascadeType.ALL)
	private Set<Student> students = new HashSet<Student>();
	public Teacher() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Teacher(String id, String name, Set<Student> students) {
		super();
		this.id = id;
		this.name = name;
		this.students = students;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Set<Student> getStudents() {
		return students;
	}
	public void setStudents(Set<Student> students) {
		this.students = students;
	}
	
	
	
	

}
           

1、測試級聯儲存

@Test
	public void test1() {
		// 獲得持久化接口對象，并開啟事務
		Session session = HibernateUtils.openSession();
		session.beginTransaction();
		// 操作
		Teacher t1 = new Teacher();
		t1.setName("張老師");
		Teacher t2 = new Teacher();
		t2.setName("李老師");

		Student s1 = new Student();
		s1.setName("張學生");
		Student s2 = new Student();
		s2.setName("李學生");

		// 維護外鍵(不執行外鍵維護的話，中間表沒有資料)
		s1.getT().add(t1);
		s2.getT().add(t2);
		// 級聯儲存
		t1.getStudents().add(s1);
		t2.getStudents().add(s2);
		session.save(t1);
		session.save(t2);
		// 送出事務，并關閉持久化接口對象
		session.getTransaction().commit();
		session.close();
           

結果：

2、測試級聯删除

@Test
	public void del() {
		// 獲得持久化接口對象，并開啟事務
		Session session = HibernateUtils.openSession();
		session.beginTransaction();
		// 操作
		Student s = session.get(Student.class, 1);
		
		session.delete(s);
		// 送出事務，并關閉持久化接口對象
		session.getTransaction().commit();
		session.close();
	}
           

結果：

    總結：執行級聯删除的時候（雙向設定級聯.all），執行删除某一個元素，隻會删除該元素在其本身表中的資料和中間表中的級聯資料。