Mysql中是blob类型，实体类定义为string，怎么取值

这个是mysql下存取blob字段的一个很简单的类，跟据自己的需要改改就行了 /** * 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:\downloads\luozsh

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())

}

}

}

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