Hibernate中，Many2One映射关系的XML实现方式

短命女 2022-09-24 00:24 101阅读 0赞

**注意: 在一对多和多对一的映射中，都可以实现，在多的一方的表里面增加一个外键。**

1、在Hibernate中，Many2One映射关系的XML实现方式

2、Student.java的代码

public class Student {
    	private int id;
    	private int age;
    	private String name;
    
    	// 持有多的一方为外键
    	private ClassRoom classRoom;
    
    	// get set

3、Student.hbm.xml的配置文件

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC 
    	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    	"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="com.hibernate.entity">
    
    	<class name="Student" table="student">
    
    		
    		<id name="id" column="id">
    			
    			<generator class="native" />
    		</id>
    
    		
    		<property name="name" column="name"></property>
    		<property name="age" column="age"></property>
    
    		
    		
    		<many-to-one name="classRoom" column="classid" />
    	</class>
    
    </hibernate-mapping>

4、ClassRoom.java的代码

public class ClassRoom {
    	private int id;
    	private String classRoomName;
    
    	// get set
    }

5、ClassRoom.hbm.xml的映射文件

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC 
    	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    	"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="com.hibernate.entity">
    
    	<class name="ClassRoom" table="classroom">
    		
    		<id name="id" column="id">
    			
    			<generator class="native" />
    		</id>
    		
    		<property name="classRoomName" column="classRoomName"></property>
    	</class>
    
    </hibernate-mapping>

6、hibernate.cfg.xml的配置

6.1  将Student.hbm.xml和ClassRoom.hbm.xml，加入到hibernate.cfg.xml的配置文件里面

<mapping resource="com/hibernate/entity/Student.hbm.xml" />
    		<mapping resource="com/hibernate/entity/ClassRoom.hbm.xml" />

6.2  hibernate.cfg.xml的配置的完整内容

<!DOCTYPE hibernate-configuration PUBLIC
    	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
    	
    	<session-factory>
    
    		
    		<property name="hibernate.connection.driver_class">
    			com.mysql.jdbc.Driver
    		</property>
    		<property name="hibernate.connection.url">
    			jdbc:mysql:///hibernate
    		</property>
    		<property name="hibernate.connection.username">root</property>
    		<property name="hibernate.connection.password">1234</property>
    		
    		<property name="hibernate.dialect">
    			org.hibernate.dialect.MySQL5Dialect
    		</property>
    
    
    		
    		
    		<property name="hibernate.show_sql">true</property>
    		
    		<property name="hibernate.format_sql">true</property>
    		
    		<property name="hibernate.hbm2ddl.auto">update</property>
    
    		
    		<mapping resource="com/hibernate/entity/Student.hbm.xml" />
    		<mapping resource="com/hibernate/entity/ClassRoom.hbm.xml" />
    	</session-factory>
    </hibernate-configuration>

7、测试代码

public class HibernateTest {
    
    	@Test
    	public void testmany2one() {
    
    		Student stu1 = new Student();
    		stu1.setAge(18);
    		stu1.setName("18");
    
    		Student stu2 = new Student();
    		stu2.setAge(19);
    		stu2.setName("19");
    
    		ClassRoom classRoom = new ClassRoom();
    		classRoom.setClassRoomName("计算机技术");
    		// 增加Student和ClassRoom的注册关系
    		stu1.setClassRoom(classRoom);
    		stu2.setClassRoom(classRoom);
    		// 保存到数据库
    		IClassRoomDao roomDao = new ClassRoomDaoImpl();
    		IStudentDao studentDao = new StudentDaoImpl();
    
    		// 在保存一的一方
    		roomDao.add(classRoom);
    		// 先保存多的一方
    
    		studentDao.add(stu1);
    		studentDao.add(stu2);
    
    	}
    
    	@Test
    	public void test02() {
    		IStudentDao studentDao = new StudentDaoImpl();
    		System.out.println(studentDao.load(1).getClassRoom());
    	}
    
    }

8、测试的运行结果

![20160721194950522][]

9、代码下载

[代码下载][Link 1]

[20160721194950522]: /images/20220720/16cfbf915b2642f29cf80868531d4baa.png
[Link 1]: http://pan.baidu.com/s/1boAmEab