java对blob的存取

此实现为用java访问mysql的blob,对图片进行存取

/**
 * Title:         BlobPros.java
 * Project:       test
 * Description:  把图片存入mysql中的blob字段，并取出
 * Call Module:  mtools数据库中的tmp表 
 * File:         C:downloadsluozsh.jpg
 * Copyright:    Copyright (c) 2003-2003
 * Company:      uniware
 * Create Date:  2002.12.5
 * @Author:      ChenQH
 * @version 1.0 版本*     
 *
 *  Revision history
 *  Name         Date     Description
 *  ----      ----        -----------
 * Chenqh   2003.12.5        对图片进行存取
 *
 * note:         要把数据库中的Blob字段设为longblob       
 *
 */

//package com.uniware;

import java.io.*;
import java.util.*;
import java.sql.*;

public class BlobPros
{
    private static final String URL = "jdbc:mysql://10.144.123.63:3306/mtools?user=wind&password=123&useUnicode=true";
    private Connection conn = null;
    private PreparedStatement pstmt = null;
    private ResultSet rs = null;
    private File file = null;
   
    public BlobPros()
    {
    }

    /**
    * 向数据库中插入一个新的BLOB对象(图片)
    * @param infile 要输入的数据文件
    * @throws java.lang.Exception
    */
   public void blobInsert(String infile) throws Exception
   {
       FileInputStream fis = null;  
           try
           {
               Class.forName("org.gjt.mm.mysql.Driver").newInstance();
               conn = DriverManager.getConnection(URL);
           
               file = new File(infile);
               fis = new FileInputStream(file);
               //InputStream fis = new FileInputStream(infile);
         pstmt = conn.prepareStatement("insert into tmp(descs,pic) values(?,?)");
         pstmt.setString(1,file.getName());    //把传过来的第一个参数设为文件名
               //pstmt.setBinaryStream(2,fis,(int)file.length());   //这种方法原理上会丢数据，因为file.length()返回的是long型
         pstmt.setBinaryStream(2,fis,fis.available());  //第二个参数为文件的内容
         pstmt.executeUpdate();
      }
           catch(Exception ex)
           {
          System.out.println("[blobInsert error : ]" + ex.toString());
           }
        finally
        {
               //关闭所打开的对像//
               pstmt.close();
               fis.close();
               conn.close();
           }
    }
   

    /**
    * 从数据库中读出BLOB对象
    * @param outfile 输出的数据文件
    * @param picID 要取的图片在数据库中的ID
    * @throws java.lang.Exception
    */

    public void blobRead(String outfile,int picID) throws Exception
    {
        FileOutputStream fos = null;
        InputStream is = null;
        byte[] Buffer = new byte[4096];
 
            try
            {
                Class.forName("org.gjt.mm.mysql.Driver").newInstance();
                conn = DriverManager.getConnection(URL);
                pstmt = conn.prepareStatement("select pic from tmp where id=?");
                pstmt.setInt(1,picID);         //传入要取的图片的ID
                rs = pstmt.executeQuery();
                rs.next();
                     
                file = new File(outfile);
                if(!file.exists())
                {
                    file.createNewFile();     //如果文件不存在，则创建
                }
                fos = new FileOutputStream(file);
                is = rs.getBinaryStream("pic");
                int size = 0;
               /* while(size != -1)
                {
                    size = is.read(Buffer);    //从数据库中一段一段的读出数据
                    //System.out.println(size);
                    if(size != -1)            //-1表示读到了文件末
                        fos.write(Buffer,0,size);
                }  */
                while((size = is.read(Buffer)) != -1)
    {
                    //System.out.println(size);
                    fos.write(Buffer,0,size);
    }
                              
         }
            catch(Exception e)
            {
                System.out.println("[OutPutFile error : ]" + e.getMessage());
            }
            finally
            {
                //关闭用到的资源
                fos.close();
                rs.close();
                pstmt.close();
                conn.close();
            }
    }
    
    public static void main(String[] args)
    {
        try
        {
           
            BlobPros blob = new BlobPros();
            //blob.blobInsert("C:Downloadsluozsh1.jpg");          
            blob.blobRead("c:/downloads/1.jpg",47);
        }
        catch(Exception e)
        {
            System.out.println("[Main func error: ]" + e.getMessage());
        }
    }
}