JPA 系列教程21-JPA2.0-@MapKeyColumn

@MapKeyColumn

用@JoinColumn注解和@MapKeyColumn处理一对多关系

ddl语句

CREATE TABLE `t_employee` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

CREATE TABLE `t_employee_map` (
  `Employee_id` bigint(20) NOT NULL,
  `emp_value` varchar(255) DEFAULT NULL,
  `emp_key` varchar(255) NOT NULL,
  PRIMARY KEY (`Employee_id`,`emp_key`),
  CONSTRAINT `FK_k06nikcsc4pc9oasboix6uagw` FOREIGN KEY (`Employee_id`) REFERENCES `t_employee` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Employee

package com.jege.jpa;

import java.util.HashMap;
import java.util.Map;

import javax.persistence.CollectionTable;
import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MapKeyColumn;
import javax.persistence.Table;

/**
 * @author JE哥
 * @email 1272434821@qq.com
 * @description:pojo模型
 */
@Entity
@Table(name = "t_employee")
public class Employee {
  @Id
  @GeneratedValue
  private Long id;
  private String name;
  @ElementCollection
  // 生成的表的主键Map.key+EmployeeMap_id
  @CollectionTable(name = "t_employee_map")
  @MapKeyColumn(name = "emp_key")
  @Column(name = "emp_value")
  private Map<String, String> others = new HashMap<String, String>();

  public Employee() {

  }

  public Employee(String name) {
    this.name = name;
  }

  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Map<String, String> getOthers() {
    return others;
  }

  public void setOthers(Map<String, String> others) {
    this.others = others;
  }



}

JPA2Test

package com.jege.jpa;

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;

public class JPA2Test {

  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();// Session
  }

  @Test
  public void persist() throws Exception {
    Employee employee = new Employee();
    employee.setName("je-ge");

    employee.getOthers().put("home", "beijing");
    employee.getOthers().put("work", "shanghai");
    entityManager.getTransaction().begin();
    entityManager.persist(employee);
    entityManager.getTransaction().commit();
  }

  @Test
  public void find() throws Exception {
    persist();
    entityManager.clear();

    Employee employee = entityManager.find(Employee.class, 1L);
    System.out.println(employee.getName());
    System.out.println(employee.getOthers());
  }

  @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();
  }

}