Hibernate应用One2Many

Hibernate应用One2Many

size=x-large]1、一对多或多对一（Group&Person 单向）[/size]
一个团队对应多名成员或多名成员对应一个团队，从单向来操作（主要看Annotation注解@）：

package com.sean.model.one2many;

import java.util.Set;

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

/**
 * 一对多：团队对象
 * 
 * @author Sean 2013-2-26
 * 
 */
@Entity
@Table(name = "p_group")
public class Group {

	private int id;
	private String name;
	private Set<Person> pset;
	
	@OneToMany
	public Set<Person> getPset() {
		return pset;
	}

	public void setPset(Set<Person> pset) {
		this.pset = pset;
	}

	@Id
	@GeneratedValue
	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;
	}

}

注意：@Table(name = "p_group")这里配置了与数据库不同的表名，原因是Hibernate在建立SQL语句时会将我们的Group类名，误解为Group By SQL语句，所以如果这里不这样配置一下就会报错。

package com.sean.model.one2many;

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

/**
 * 一对多：成员对象
 * 
 * @author Sean 2013-2-26
 * 
 */
@Entity
public class Person {

	private int id;
	private String name;
	private Group group;

	public Group getGroup() {
		return group;
	}

	public void setGroup(Group group) {
		this.group = group;
	}

	@Id
	@GeneratedValue
	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;
	}

}

从这里可以看出一对多或多对一，只需要对为一的那边设置@OneToMany，可想而知，双向的操作就是对为多的那边设置@ManyToOne就可以了，请看下面。

2、一对多或多对一（Group&Person 双向）
一个团队对应多名成员或多名成员对应一个团队，从双向来操作（主要看Annotation注解@）：

Group类：

package com.sean.model.one2many;

import java.util.Set;

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

/**
 * 一对多：团队对象
 * 
 * @author Sean 2013-2-26
 * 
 */
@Entity
@Table(name = "p_group")
public class Group {

	private int id;
	private String name;
	private Set<Person> pset;
	
	@OneToMany
	public Set<Person> getPset() {
		return pset;
	}

	public void setPset(Set<Person> pset) {
		this.pset = pset;
	}

	@Id
	@GeneratedValue
	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;
	}

}

Person类：

package com.sean.model.one2many;

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

/**
 * 一对多：成员对象
 * 
 * @author Sean 2013-2-26
 * 
 */
@Entity
public class Person {

	private int id;
	private String name;
	private Group group;
         @ManyToOne
	public Group getGroup() {
		return group;
	}

	public void setGroup(Group group) {
		this.group = group;
	}

	@Id
	@GeneratedValue
	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;
	}

}

评论

1 楼 jeson0725 2013-05-15