JPA 系列教程13-复合主键-@EmbeddedId+@Embeddable

2023-01-04 20:19:48

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和复合主键-2个@Id+@IdClass一样

Airline

package com.jege.jpa.embedded;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

import javax.persistence.Table;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:复合主键-@EmbeddedId

 */

@Entity

@Table(name = "t_airline")

public class Airline {

  @EmbeddedId

  private AirlinePK pk;

  private String name;

  public Airline() {

  }

  public Airline(AirlinePK pk, String name) {

    this.pk = pk;

    this.name = name;

  }

  public Airline(String startCity, String endCity, String name) {

    pk = new AirlinePK(startCity, endCity);

    this.name = name;

  }

  public AirlinePK getPk() {

    return pk;

  }

  public void setPk(AirlinePK pk) {

    this.pk = pk;

  }

  public String getName() {

    return name;

  }

  public void setName(String name) {

    this.name = name;

  }

  @Override

  public String toString() {

    return "Airline [pk=" + pk + ", name=" + name + "]";

  }

}

AirlinePK

package com.jege.jpa.embedded;

import java.io.Serializable;

import javax.persistence.Column;

import javax.persistence.Embeddable;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:复合主键-@Embeddable

 */

@Embeddable

public class AirlinePK implements Serializable {

  private static final long serialVersionUID = 2836348182939717563L;

  @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;

  }

  @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;

  }

  @Override

  public String toString() {

    return "AirlinePK [startCity=" + startCity + ", endCity=" + endCity + "]";

  }

}

MainTest

package com.jege.jpa.embedded;

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;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:复合主键@EmbeddedId+@Embeddable测试

 */

public class MainTest {

  private static EntityManagerFactory entityManagerFactory = null;

  private EntityManager entityManager = null;

  @BeforeClass

  public static void setUpBeforeClass() throws Exception {

    entityManagerFactory = Persistence.createEntityManagerFactory("com.jege.jpa");

  }

  @Before

  public void setUp() throws Exception {

    entityManager = entityManagerFactory.createEntityManager();

  }

  @Test

  public void persist() {

    Airline airline = new Airline("PEK", "SHA", "北京飞上海");

    airline.setName("北京飞上海");

    entityManager.getTransaction().begin();

    entityManager.persist(airline);

    entityManager.getTransaction().commit();

  }

  @Test

  public void find() {

    persist();

    AirlinePK pk = new AirlinePK("PEK", "SHA");

    Airline airline = entityManager.find(Airline.class, pk);

    System.out.println(airline);

  }

  @After

  public void tearDown() throws Exception {

    if (entityManager != null && entityManager.isOpen())

      entityManager.close();

  }

  @AfterClass

  public static void tearDownAfterClass() throws Exception {

    if (entityManagerFactory != null && entityManagerFactory.isOpen())

      entityManagerFactory.close();

  }

}

http://blog.csdn.net/je_ge/article/details/53678164