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

CREATE TABLE `t_airline` (

  `startCity` varchar(3) NOT NULL,

  `endCity` varchar(3) NOT NULL,

  `name` varchar(255) DEFAULT NULL,

  PRIMARY KEY (`startCity`,`endCity`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

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.Table;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:复合主键-2个@Id

 */

@Entity

@Table(name = "t_airline")

public class Airline implements Serializable {

  private static final long serialVersionUID = -906357110051689484L;

  @Id

  @Column(length = 3)

  private String startCity;

  @Id

  @Column(length = 3)

  private String endCity;

  private String 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;

  }

  public String getName() {

    return name;

  }

  public void setName(String name) {

    this.name = name;

  }

  @Override

  public String toString() {

    return "Airline [startCity=" + startCity + ", endCity=" + endCity + ", name=" + name + "]";

  }

}

MainTest

package com.jege.jpa.composite;

import javax.persistence.EntityManager;

import javax.persistence.EntityManagerFactory;

import javax.persistence.Persistence;

import javax.persistence.PersistenceException;

import org.junit.Test;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:复合主键-2个@Id测试

 */

public class MainTest {

  @Test

  public void crud() {

    EntityManagerFactory entityManagerFactory = null;

    EntityManager entityManager = null;

    try {

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

      entityManager = entityManagerFactory.createEntityManager();

      Airline airline = new Airline();

      airline.setStartCity("PEK");

      airline.setEndCity("SHA");

      airline.setName("bj to sh");// 新建状态

      entityManager.getTransaction().begin();

      entityManager.persist(airline);// 托管状态

      airline.setName("北京飞上海");

      entityManager.getTransaction().commit();

      Airline airline1 = new Airline();

      airline1.setStartCity("PEK");

      airline1.setEndCity("SHA");

      // hibernate:瞬时状态，持久状态(托管)，游离(脱管)状态

      airline1 = entityManager.find(Airline.class, airline1);

      System.out.println("name:" + airline1.getName());

      entityManager.getTransaction().begin();

      entityManager.remove(airline1);

      entityManager.getTransaction().commit();

      // airline1变为删除状态

      entityManager.getTransaction().begin();

      entityManager.persist(airline1);

      entityManager.getTransaction().commit();

    } catch (PersistenceException e) {

      e.printStackTrace();

      entityManager.getTransaction().rollback();

      throw e;

    } finally {

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

    entityManager.close();// 游离状态

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

    entityManagerFactory.close();

    }

  }

}

源码地址

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

如果觉得我的文章对您有帮助,请打赏支持。您的支持将鼓励我继续创作!谢谢！