复合主键

指多个主键联合形成一个主键组合

需求产生

比如航线一般是由出发地及目的地确定，如果要确定唯一的航线就可以用出发地和目的地一起来表示

ddl语句

同复合主键-2个@Id一样

Airline

package com.jege.jpa.composite;import java.io.Serializable;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.Table;/*** @author JE哥* @email 1272434821@qq.com* @description:复合主键-2个@Id+@IdClass*/
@Entity
@Table(name = "t_airline")
@IdClass(Airline.AirlinePK.class)
public class Airline {@Idprivate String startCity;@Idprivate String endCity;private String name;public String getName() {return name;}public void setName(String name) {this.name = name;}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;}@Overridepublic String toString() {return "Airline [startCity=" + startCity + ", endCity=" + endCity + ", name=" + name + "]";}// 必须static的classpublic static class AirlinePK implements Serializable {private static final long serialVersionUID = -7189167162738318201L;@Column(length = 3, nullable = false)private String startCity;@Column(length = 3, nullable = false)private String endCity;public AirlinePK() {}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;}@Overridepublic 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;}@Overridepublic 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;}@Overridepublic String toString() {return "AirlinePK [startCity=" + startCity + ", endCity=" + endCity + "]";}}}

MainTest

package com.jege.jpa.composite;import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;import com.jege.jpa.composite.Airline.AirlinePK;/*** @author JE哥* @email 1272434821@qq.com* @description:复合主键-2个@Id+@IdClass测试*/
public class MainTest {private static EntityManagerFactory entityManagerFactory = null;private EntityManager entityManager = null;@BeforeClasspublic static void setUpBeforeClass() throws Exception {entityManagerFactory = Persistence.createEntityManagerFactory("com.jege.jpa");}@Beforepublic void setUp() throws Exception {entityManager = entityManagerFactory.createEntityManager();}@Testpublic void persist() {Airline airline = new Airline();airline.setEndCity("SHA");airline.setStartCity("PEK");airline.setName("北京飞上海");entityManager.getTransaction().begin();entityManager.persist(airline);entityManager.getTransaction().commit();}@Testpublic void find() {persist();AirlinePK pk = new AirlinePK("PEK", "SHA");Airline airline = entityManager.find(Airline.class, pk);System.out.println(airline);}@Afterpublic void tearDown() throws Exception {if (entityManager != null && entityManager.isOpen())entityManager.close();}@AfterClasspublic static void tearDownAfterClass() throws Exception {if (entityManagerFactory != null && entityManagerFactory.isOpen())entityManagerFactory.close();}
}

其他关联项目

• JPA 系列教程11-复合主键-2个@Id
  http://blog.csdn.net/je_ge/article/details/53678085

源码地址

https://github.com/je-ge/jpa

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