如何用JAVA将二进制文件转换成BASE64格式保存到MySQL的Blob字段里并读出下载

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/wilsonyun/article/details/77867438

由于需求要将上传的文件以BASE64的方式保存到MySQL的Blob字段，并可以读取Blob字段下载生成文件，方法如下：

1、下载用于BASE64编码转换的sun.misc.BASE64Decoder和sun.misc.BASE64Encoder的支持库（jar)，放到运行库中。

2.   实现代码如下：

package com.pszx.venus;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;



import com.pszx.venus.DBConnector;
import com.sun.org.apache.xml.internal.security.utils.Base64;



public class upLoadFileToDB {
	
	public void upLoadFile() throws Exception{
		String fileName = "d:\\finish3.png";
		
		File file = new File(fileName);
		FileInputStream fin = new FileInputStream(file);
		
		byte[] buffer = new byte[(int)file.length()];
		
		fin.read(buffer);
		fin.close();
		
		DBConnector dbc = new DBConnector();
		Connection conn = dbc.createConn();
		PreparedStatement pstmt = null;
		conn.setAutoCommit(false);
		
		String sql = "";
		try{
		
			String sql1 = "update sample set fj=?, bz=?  where id=1 ";
			
			pstmt = conn.prepareStatement(sql1);
			pstmt.setString(1, new BASE64Encoder().encode(buffer));  //将文件内容编码成base64格式后以字符串的方式保存到Blob字段中
			pstmt.setString(2, "wilson");
			
			
			pstmt.executeUpdate();
			conn.commit();
			
			
		        //从数据库中读出
			sql1 = "select fj from sample where id=1";
			pstmt = conn.prepareStatement(sql1);
			
			
			ResultSet rs = pstmt.executeQuery();
			
			byte[] binfl = null; 
			while(rs.next()){
				
				Blob b = rs.getBlob("fj");       //从Blob字段中读出base64格式的内容
				byte[] ba = b.getBytes(1, (int)b.length());
				binfl = Base64.decode(ba);      //将base64格式解码              
				
				
			}
			

			String fileName1= "d:\\finish4.png";
			
			File file1 = new File(fileName1);
			
			FileOutputStream fout = new FileOutputStream(file1);
			
			fout.write(binfl);    //将解码后的内容写入文件
			fout.close();
			
			
		}finally{
			pstmt.close();
			conn.close();
			dbc.disConnect();
		}
	}
	
	public static void main(String[] args) throws Exception{
		upLoadFileToDB lf = new upLoadFileToDB();
		
		lf.upLoadFile();
		
	}

}