JPA（六）之联合主键

为什么80%的码农都做不了架构师？>>>   

1.顾名思义：复合主键就是指多个主键联合形成一个主键组合

2.背景介绍：比如原则上航线是由出发地及目的地确定，所以，如果要设置航线的id可以用出发地和目的地来表示。

3.persistence.xml内容不变

4.实体bean

  主键类：

 

package com.sinoi.bean;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Embeddable;

@Embeddable
public class AirlinePK implements Serializable{
	@Column(length=3, nullable=false)
	private String startCity;
	@Column(length=3, nullable=false)
	private String endCity;

	public AirlinePK(String startCity, String endCity) {
		this.startCity = startCity;
		this.endCity = endCity;
	}
	
	public String getStartCity() {
		return startCity;
	}
	public void setStartCity(String startCity) {
		this.startCity = startCity;
	}
	public String getEndCity() {
		return endCity;
	}
	public void setEndCity(String endCity) {
		this.endCity = endCity;
	}
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((endCity == null) ? 0 : endCity.hashCode());
		result = prime * result
				+ ((startCity == null) ? 0 : startCity.hashCode());
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		AirlinePK other = (AirlinePK) obj;
		if (endCity == null) {
			if (other.endCity != null)
				return false;
		} else if (!endCity.equals(other.endCity))
			return false;
		if (startCity == null) {
			if (other.startCity != null)
				return false;
		} else if (!startCity.equals(other.startCity))
			return false;
		return true;
	}
	
	
}

 

航线类：

package com.sinoi.bean;

import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

@Entity
public class Airline {
	@EmbeddedId
	private AirlinePK id;
	@Column(length=10, nullable=false)
	private String name;
	
	public Airline() {}
	
	public Airline(String startCity, String endCity, String name) {
		this.id = new AirlinePK(startCity, endCity);
		this.name = name;
	}
	
	public AirlinePK getId() {
		return id;
	}
	public void setId(AirlinePK id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
}

 

5.测试

 

package junit.test;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.Test;

import com.sinoi.bean.Airline;


public class UnitTest {
	@Test
	public void save() {
		EntityManagerFactory factory = Persistence.createEntityManagerFactory("unitname");
		EntityManager manager = factory.createEntityManager();
		manager.getTransaction().begin();
		
		manager.persist(new Airline("PEK", "SHA", "PeToShang"));
		
		manager.getTransaction().commit();
		manager.close();
		factory.close();
	}
}

 

 

转载于:https://my.oschina.net/beanGo/blog/168993