hibernate中大对象的存储

Dear 丶 2022-06-12 03:50 151阅读 0赞

有时候我们的实体类中某一个属性里面的放的数据量稍多的时候，使用String已经不能满足需要了，例如，简介或者是图片等，里面的值可能很大，这个时候，就需要使用大对象来存放数据，当然像图片之类的，大部分情况下，是将图片本身存放在图片服务器上，数据库中只放一个这个图片所在服务器的地址即可，但是免不了有一些情况，我们不会单独放大数据放入磁盘，而是直接存到数据库中，这个时候就用到了Blob和Clob这两个大对象，接下来我们就来学习一下这个两个对象在hibernate中的使用。

新建一个java项目，取名为：07hibernate\_bigObject

项目结构如图：

![Center][]

需要的jar包，请参见《[Hibernate环境搭建和配置][Hibernate]》

新建一个实体类student，代码如下：

package com.robert.pojo;
    
    import java.sql.Blob;
    import java.sql.Clob;
    
    public class Student {
    
    	private int id ;
    	private String name ;
    	private int age ;
    	//存放大数据，可以存放4G内容
    	private Blob image ;
    	private Clob introduce ;
    	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 int getAge() {
    		return age;
    	}
    	public void setAge(int age) {
    		this.age = age;
    	}
    	public Blob getImage() {
    		return image;
    	}
    	public void setImage(Blob image) {
    		this.image = image;
    	}
    	public Clob getIntroduce() {
    		return introduce;
    	}
    	public void setIntroduce(Clob introduce) {
    		this.introduce = introduce;
    	}
    	
    	
    }

其中image用来存放图片的二进制文件，

introduce用来存放学生的简介信息

Student.hbm.xml配置文件的代码：

<?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="Student" table="student">
    		<id name="id">
    			<generator class="native"></generator>
    		</id>
    		<property name="name"></property>
    		<property name="age"></property>
    		<property name="image" type="blob"></property>
    		<property name="introduce" type="clob"></property>
    		
    	</class>
    </hibernate-mapping>

其中，image和introduce都需要指定type

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/Student.hbm.xml" />
    
    </session-factory>
    </hibernate-configuration>

HibernateUtil类代码：

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测试类代码：

package com.robert.test;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    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.Student;
    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();
    			
    			Student stu = new Student() ;
    			stu.setName("嘻嘻") ;
    			stu.setAge(23) ;
    			String fileStr = "C:/Users/Public/Pictures/Sample Pictures/shamo.jpg" ;
    			Blob blob=new SerialBlob(getByteFromFile(fileStr)) ;
    			Clob clob = new SerialClob("tttt".toCharArray()) ;
    			stu.setImage(blob) ;
    			stu.setIntroduce(clob);
    			
    			session.save(stu);
    			tx.commit();
    			
    		} catch (HibernateException e) {
    			if(tx!=null) {
    				tx.rollback();
    			}
    			e.printStackTrace();
    			throw e ;
    		}finally {
    			HibernateUtil.closeSession() ;
    		}
    	}
    
    	/**
    	 * 读取磁盘中文件，返回字节码
    	 * @param fileStr
    	 * @return
    	 * @throws IOException
    	 */
    	private byte[] getByteFromFile(String fileStr) throws IOException {
    		FileInputStream fis = new FileInputStream(new File(fileStr)) ;
    		byte[] read = new byte[1024] ;
    		int len = 0 ;
    		StringBuffer sb = new StringBuffer() ;
    		while ((len = fis.read(read))!=-1) {
    			sb.append(read.toString()) ;
    		}
    		return sb.toString().getBytes();
    	}	
    }

[Center]: /images/20220612/3dfa3303a81843d58c917de631d2ca76.png
[Hibernate]: http://blog.csdn.net/u011159417/article/details/75014665