hibernate组件映射

客官°小女子只卖身不卖艺 2022-06-12 04:22 207阅读 0赞

我们有时候有一张数据库表，但是这个数据库表中有几列的数据都是类似的，可以使用一个独立的实体类来表示，这个就叫做组件映射，即有个实体类或者多个实体类对应一张数据库表，遇到这个组件映射的情况我们该怎么配置hibernate的实体类配置文件呢？今天就来说说这个问题---组件映射。

新建一个新的java项目，名称为：07hibernate\_component

结构如图：

![Center][]

需要的jar可以参见《[Hibernate环境搭建和配置][Hibernate]》

新建一个实体类Teacher，代码如下：

package com.robert.pojo;
    
    public class Teacher {
    
    	private int id ;
    	private String name ;
    	private String sex ;
    	private Address address ;
    	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;
    	}
    	public String getSex() {
    		return sex;
    	}
    	public void setSex(String sex) {
    		this.sex = sex;
    	}
    	public Address getAddress() {
    		return address;
    	}
    	public void setAddress(Address address) {
    		this.address = address;
    	}
    	
    	
    }

Teacher类对应的额组件是Address（也就是Teacher的地址组件），代码如图：

package com.robert.pojo;
    
    public class Address {
    
    	private String addr1 ;
    	private String addr2 ;
    	private String addr3 ;
    	public String getAddr1() {
    		return addr1;
    	}
    	public void setAddr1(String addr1) {
    		this.addr1 = addr1;
    	}
    	public String getAddr2() {
    		return addr2;
    	}
    	public void setAddr2(String addr2) {
    		this.addr2 = addr2;
    	}
    	public String getAddr3() {
    		return addr3;
    	}
    	public void setAddr3(String addr3) {
    		this.addr3 = addr3;
    	}
    	
    }

Teacher.hbm.xml配置文件代码：

<?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.robert.pojo">
    	<class name="Teacher">
    		<id name="id">
    			<generator class="native"></generator>
    		</id>
    		<property name="name"></property>
    		<property name="sex"></property>
    		
    		<component name="address" class="Address">
    			<property name="addr1"></property>
    			<property name="addr2"></property>
    			<property name="addr3"></property>
    		</component>
    	</class>
    </hibernate-mapping>

Teacher.hbm.xml中配置文件和Teacher、Address关系如图：

![Center 1][]

hibernate.cfg.xml配置文件代码：

<!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="connection.driver_class">
    		com.mysql.jdbc.Driver
    	</property>
    	<property name="connection.url">jdbc:mysql:///hibernate4</property>
    	<property name="connection.username">root</property>
    	<property name="connection.password">root</property>
    	
    	<property name="hibernate.dialect">
    		org.hibernate.dialect.MySQL5Dialect
    	</property>
    	
    	<property name="show_sql">true</property>
    	
    	<property name="format_sql">true</property>
    	
    	<property name="hbm2ddl.auto">update</property>
    
    	
    	<mapping resource="com/robert/pojo/Teacher.hbm.xml" />
    
    </session-factory>
    </hibernate-configuration>

HibernateUtil代码如下：

package com.robert.util;
    
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
    import org.hibernate.cfg.Configuration;
    
    public class HibernateUtil {
    
    	private static Configuration cfg = null;
    	private static SessionFactory factory = null;
    	private static Session session = null ;
    	
    	static {
    		init();
    	}
    
    	public static void init() {
    		cfg = new Configuration().configure();
    		factory = cfg.buildSessionFactory(new StandardServiceRegistryBuilder()
    				.applySettings(cfg.getProperties()).build());
    	}
    
    	public static Session getSession() {
    		if (factory != null){
    			return session = factory.openSession();
    		}
    		
    
    		init();
    		return session = factory.openSession();
    	}
    	
    	public static void closeSession() {
    		if(session!=null && session.isOpen())
    			session.close();
    	}
    
    }

HIbernateTest测试类的代码如下：

package com.robert.test;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.sql.Blob;
    import java.sql.Clob;
    import java.sql.SQLException;
    
    import javax.sql.rowset.serial.SerialBlob;
    import javax.sql.rowset.serial.SerialClob;
    import javax.sql.rowset.serial.SerialException;
    
    import org.hibernate.HibernateException;
    import org.hibernate.Session;
    import org.hibernate.Transaction;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.tool.hbm2ddl.SchemaExport;
    import org.junit.Test;
    
    import com.robert.pojo.Address;
    import com.robert.pojo.Teacher;
    import com.robert.util.HibernateUtil;
    
    public class HibernateTest {
    
    	/**
    	 * 根据*.hbm.xml文件对应的生成数据库表
    	 */
    	@Test
    	public void testCreateDB() {
    		Configuration cfg = new Configuration().configure();
    		SchemaExport se = new SchemaExport(cfg);
    		// 第一个参数：是否生成ddl脚本
    		// 第二个参数：是否执行到数据库中
    		se.create(true, true);
    	}
    
    	/**
    	 * @throws HibernateException
    	 * @throws SerialException
    	 * @throws SQLException
    	 * @throws IOException
    	 */
    	@Test
    	public void testSave() throws HibernateException, SerialException,
    			SQLException, IOException {
    		Session session = null;
    		Transaction tx = null;
    		try {
    			session = HibernateUtil.getSession();
    			tx = session.beginTransaction();
    
    			Teacher t = new Teacher();
    			t.setName("老张");
    			t.setSex("男");
    			Address address = new Address();
    			address.setAddr1("北京朝阳");
    			address.setAddr2("东城区");
    			address.setAddr3("西城区");
    			t.setAddress(address) ;
    			
    			session.save(t);
    			
    			tx.commit();
    
    		} catch (HibernateException e) {
    			if (tx != null) {
    				tx.rollback();
    			}
    			e.printStackTrace();
    			throw e;
    		} finally {
    			HibernateUtil.closeSession();
    		}
    	}
    
    }

使用Junit4执行数据库表生成语句，如图：

![Center 2][]

使用Junit4实行testSave方法，将数据存入数据库表Teacher中，如图：

![Center 3][]

数据库表中的数据如图：

![Center 4][]

[Center]: /images/20220612/c272f8ce70fb4127981ce35aa80d6650.png
[Hibernate]: http://blog.csdn.net/u011159417/article/details/75014665
[Center 1]: /images/20220612/b28064f09f8345a0abec5fbbb732bb69.png
[Center 2]: /images/20220612/cfb05a25d3204ee3805285aede8454b0.png
[Center 3]: /images/20220612/72272fea43d7445fb26fe77ef0ebbbff.png
[Center 4]: /images/20220612/92c633423f554bd4881f8635d6d2be5e.png