Hibernate的那些事-manyToOne注解映射(Map集合)

1：多对一的一方：

package collections.map;

import java.util.HashMap;

import java.util.Map;

import javax.persistence.CascadeType;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.MapKey;

import javax.persistence.OneToMany;

import javax.persistence.Table;

@Entity

@Table(name = "t_map_group")

public class Group {

 private int id;

 private String name;

 private Map<Integer,User> users = new HashMap<Integer,User>();

 @Id

 @GeneratedValue

 public int getId() {

  return id;

 }

 public void setId(int id) {

  this.id = id;

 }

 public String getName() {

  return name;

 }

 public void setName(String name) {

  this.name = name;

 }
 @OneToMany(mappedBy = "group", cascade = { CascadeType.ALL })

 @MapKey(name="id")

 public Map<Integer, User> getUsers() {

  return users;

 }

 public void setUsers(Map<Integer, User> users) {

  this.users = users;

 }

 

 

}

2：多对一的多方：

package collections.map;

import javax.persistence.CascadeType;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

import javax.persistence.Table;

@Entity

@Table(name = "t_map_user")

public class User {

 private int id;

 private String name;

 private Group group;

 @ManyToOne(cascade = CascadeType.ALL)

 /*@ManyToOne就是要生成一个外键去关联它的关联类

  * 如果没有下面这个注解也会将在User实体对应的数据表中产生一个外键字段，它是参照Group的主键*/

 @JoinColumn(name="groupid")
 public Group getGroup() {

  return group;

 }

 public void setGroup(Group group) {

  this.group = group;

 }

 @Id

 @GeneratedValue

 public int getId() {

  return id;

 }

 public void setId(int id) {

  this.id = id;

 }

 public String getName() {

  return name;

 }

 public void setName(String name) {

  this.name = name;

 }

}

3：在映射文件的配置：

<mapping class="collections.map.Group" />

  <mapping class="collections.map.User" />

4：使用Junit进行测试

package collections.map;

import java.util.Map;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

//import org.hibernate.tool.hbm2ddl.SchemaExport;

import org.junit.AfterClass;

import org.junit.BeforeClass;

import org.junit.Test;

public class TestMapJunit {

 /**

  * @param args

  */

 

 private static SessionFactory sessionFactory;

 @BeforeClass

 public static void beforClass(){

 new SchemaExport(new AnnotationConfiguration().//生成表结构

   configure()).create(false, true);

  

  sessionFactory = new AnnotationConfiguration ().configure()

  .buildSessionFactory();

  

 }

 @AfterClass

 public static void afterClass(){

  if(sessionFactory!=null){

   sessionFactory.close();

  }

  

 }

 @Test

 public void testSavaEntity(){

 Session session =sessionFactory.getCurrentSession();

 session.beginTransaction();

 

 Group group=new Group();

 group.setName("kewen");

 User user =new User();

 user.setName("myDog");

 user.setGroup(group);

 User user1 =new User();

 user1.setName("myCat");

 user1.setGroup(group);

 

 group.getUsers().put(user.getId(), user);

 group.getUsers().put(user1.getId(), user1);

 

 session.save(group);

 session.save(user);

 session.save(user1);

 session.getTransaction().commit();

  

 }

 @Test

 public void loadGroupAndUser(){

  
4000
sessionFactory = new AnnotationConfiguration ().configure()

  .buildSessionFactory();

  Session session=sessionFactory.getCurrentSession();

  session.beginTransaction();

  Group g=(Group)session.load(Group.class, 1);

  

  

  for(Map.Entry<Integer,User> entry:g.getUsers().entrySet()){

   System.out.println(entry.getValue().getId()+entry.getValue().getName());

  }

  session.getTransaction().commit();

  

  

 }
 public static  void main(String [] args){

  

  beforClass();

 }

}