hibernate存取囄��C�Z��

路易 — Thu, 28 Dec 2006 11:26:00 GMT

一般网站在处理用户上传囄��旉��常采用两种�{�略�Q�一是直接把囄��存入数据库中的Blob字段�Q�二是数据库中只存储囄��的在服务器上的�\径信息，囄��存放在分门别�cȝ��文�g中，使用的时候从数据库读取�\径信息到��面img元素卛_��Q�在此不讨论两种�Ҏ��的优劣，我只是写了个hibernate的例子来实现�W�一�U�策略．例子很简单，t_user表主要两个字�D�，name和photo�Q�其中photo字段�c�d��为Blob�Q�在此例中数据库我采用mysql�Q�oracle的Blob字段比较�Ҏ��Q�你必须自定义类型，具体的请自行搜烦�Q�这斚w��的资料很多．

//User.java　　

package com.denny_blue.hibernate;

import java.io.Serializable;
import java.sql.Blob;

public class User implements Serializable{
private Integer id;
private String name;
private Blob photo;
/**
  * @return the id
  */
public User(){
}
public Integer getId() {
  return id;
}
/**
  * @param id the id to set
  */
public void setId(Integer id) {
  this.id = id;
}
/**
  * @return the name
  */
public String getName() {
  return name;
}
/**
  * @param name the name to set
  */
public void setName(String name) {
  this.name = name;
}
/**
  * @return the photo
  */
public Blob getPhoto() {
  return photo;
}
/**
  * @param photo the photo to set
  */
public void setPhoto(Blob photo) {
  this.photo = photo;
}

}

�c�User有３个属性，id,name,photo�Q�相应的getter和setter�Ҏ��以及一个无参构造函敎ͼ�应该注意的是photo的类型java.sql.Blob

相应的user.hbm.xml应该如下�Q?br />

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
" http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd ">

package="com.denny_blue.hibernate">

         table="t_user"
        dynamic-update="true"
        dynamic-insert="true"
        batch-size="3">
        column="id"
      type="java.lang.Integer">





对应的hibernate.cfg.xml配置文�g�Q�不再列出，请参照hibernate文档自行讑֮��Q?br />
�Q��O�Q�做了这一步，我们写个��试�c�L��q�行单元��试�Q?br />
package com.denny_blue.test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Blob;

import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.denny_blue.hibernate.User;

import junit.framework.TestCase;

public class HibernateTest extends TestCase {
        private Session session;
protected void setUp() throws Exception {
  try{
   Configuration config=new Configuration().configure();
   SessionFactory sf=config.buildSessionFactory();
   session=sf.openSession();
  }catch(HibernateException e){
   e.printStackTrace();
  }
}

protected void tearDown() throws Exception {
  try{
   session.close();
  }catch(HibernateException e){
   e.printStackTrace();
  }
}

public void testSave()throws FileNotFoundException,IOException{
  User user=new User();
  user.setName("jordan");
  FileInputStream in=new FileInputStream("C:\\test.gif");
  Blob photo=Hibernate.createBlob(in);
  user.setPhoto(photo);
  Transaction tx=null;
  try{
  tx=session.beginTransaction();
  session.saveOrUpdate(user);
  tx.commit();
  }catch(HibernateException e){
   if(tx!=null)
    tx.rollback();
   e.printStackTrace();
  }finally{
   in.close();
  }
}
public void testLoad()throws Exception{
  try{
   User user=(User)session.load(User.class, new Integer(1));
   Blob photo=user.getPhoto();
   InputStream in=photo.getBinaryStream();
   FileOutputStream out=new FileOutputStream("C:\\out\\test2.gif");
   byte [] buf=new byte[1024];
   int len;
   while((len=in.read(buf))!=-1){
    out.write(buf, 0, len);
   }
   in.close();
   out.close();
  }catch(HibernateException e){
   e.printStackTrace();
  }
}

}
我们��d��C盘目录下的test.gif�q�存储到数据库中�Q�然后再取出来写入C:\out目录�Q�此时你可以查看下数据表中photo昄��为blob,表示已经成功存入�Q�值的注意的代码片�D�就是：

FileInputStream in=new FileInputStream("C:\\test.gif");
  Blob photo=Hibernate.createBlob(in);
我们�q�里是从��盘中读取图片，实际应用中你可以利用上传�l��g得到囄��的２�q�制数据��，�q�利用Hibernate.createBlob�Ҏ��来构造相应的Blob对象�Q�而取囄��则��?br />
InputStream in=photo.getBinaryStream();

�q�只是个��单的��试�c�，如果我想从数据库中取出图片�ƈ现实在页面上该如何做呢？其实也很��单，我们先要写一个servlet�Q�在它的service�Ҏ��中取出图片，�qӞ��画＂到指定页面上�Q?br />
package com.easyjf.asp.action;

import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Blob;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import com.denny)blue.hibernate.User;

public class Test extends HttpServlet {

/**
  * Destruction of the servlet.

  */
private Session session;
public void destroy() {
  try{
   session.close();
  }catch(HibernateException e){
   e.printStackTrace();
  }
}

/**
  * Initialization of the servlet.

  *
  * @throws ServletException if an error occure
  */
public void init() throws ServletException {
  try{
   Configuration config=new Configuration().configure();
   SessionFactory sf=config.buildSessionFactory();
   session=sf.openSession();
  }catch(HibernateException e){
   e.printStackTrace();
  }
}
    public void doGet(HttpServletRequest request,HttpServletResponse response)
    {
     try{
   User user=(User)session.load(User.class, new Integer(1));
   Blob photo=user.getPhoto();
   InputStream in=photo.getBinaryStream();
   OutputStream out=response.getOutputStream();
   byte [] buf=new byte[1024];
   int len;
   while((len=in.read(buf))!=-1){
    out.write(buf, 0, len);
   }
   in.close();
   out.close();
  }catch(Exception e){
   e.printStackTrace();
  }
    }

}

通过response.getOutputStream取得输出��，其他��׃��上段代码一��_��servlet写好了，怎么在页面调用呢�Q�那��更��单啦�Q�直接在��面的img标签的src属性上调用该servlet卛_��Q�如�Q?br />

路易 2006-12-28 19:26 发表评论

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hibernate存取囄����C�Z��

hibernate存取囄��C�Z��