多对多单向外键关联

1、在其中一方引入另一方的集合并在其get方法上加上注解@ManyToMany默认会生成一张以两个对象名称组合的中间表

2、中间表的名称和字段名称都可以修改

多对多的案例太多此次拿着最常见的Student和Teacher进行举例

1、创建Teacher做主控

package cn.yinghuo.model;

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

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;

import org.hibernate.annotations.GenericGenerator;

/**
 * 多对多单向外键关联
 * 主控
 */
	@Entity
	public class Teacher {
		public String tid;
		public String tname;
		public Set<Student> students = new HashSet<>();
		
	@ManyToMany
	@JoinTable(name="t_s",
		joinColumns={@JoinColumn(name="tid")},
		inverseJoinColumns={@JoinColumn(name="sid")}
	)

	public Set<Student> getStudents() {
		return students;
	}
	public void setStudents(Set<Student> students) {
		this.students = students;
	}
	
	@Id
	@GeneratedValue(generator="uuid")
	@GenericGenerator(name = "uuid", strategy = "uuid")
	public String getTid() {
		return tid;
	}
	public void setTid(String tid) {
		this.tid = tid;
	}
	public String getTname() {
		return tname;
	}
	public void setTname(String tname) {
		this.tname = tname;
	}
}

2、创建Student做被控

package cn.yinghuo.model;

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

import org.hibernate.annotations.GenericGenerator;

/**
 * 多对多单向外键关联
 * 被控
 */
	@Entity
	public class Student {
		public String sid;
		public String sname;
	
	@Id
	@GeneratedValue(generator="uuid")
	@GenericGenerator(name = "uuid", strategy = "uuid")
	public String getSid() {
		return sid;
	}
	public void setSid(String sid) {
		this.sid = sid;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
}

3、创建测试类

package cn.yinghuo.action;
/**
 * 测试类
 */
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
 
public class Main {
	public static void main(String[] args) {
		schemaExport();
	}
	
	// schemaExport()生成数据库表
	// 第一个true是在控制台打印出DDL，如果是false没什么影响只是不再打印出DDL(数据库定义语言)
	// 第二个true是创建表,反之false则不创建
	public static void schemaExport() {
		new SchemaExport(new Configuration().configure()).create(true, true);
	}
}

4、在XML中引入映射文件

5、查看模型