使用Java MD5 为文件和字符串加密

package com.kaige123.util;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;

import java.security.MessageDigest;

/**

 * MD5文字和文件加密<br>

 * http://www.kaige123.com

 * @author 凯哥

 */

public class MD5Util {

         //16进制

         protected static char hex[] = {

                            ’0’, ’1’, ’2’, ’3’, ’4’, ’5’, ’6’,’7’, ’8’, ’9’, ’A’, ’B’, ’C’, ’D’, ’E’, ’F’};

         protected static MessageDigest messagedigest = null;

         static {

                   try {

                            //得到MD5实例

                            messagedigest = MessageDigest.getInstance("MD5");

                   } catch (Exception e) {

                   }

         }

         //得到文件MD5钥匙

         public static String getFileMD5String(File file) throws IOException {

                   FileInputStream in = new FileInputStream(file);

                   FileChannel ch = in.getChannel();

                   MappedByteBuffer byteBuffer =

                                     ch.map(FileChannel.MapMode.READ_ONLY, 0,

                                     file.length());

                   messagedigest.update(byteBuffer);

                   return bufferToHex(messagedigest.digest());

         }

         //得到MD5字符串钥匙

         public static String getMD5String(String s) {

                   return getMD5String(s.getBytes());

         }

         public static String getMD5String(byte[] bytes) {

                   messagedigest.update(bytes);

                   return bufferToHex(messagedigest.digest());

         }

         private static String bufferToHex(byte bytes[]) {

                   return bufferToHex(bytes, 0, bytes.length);

         }

         private static String bufferToHex(byte bytes[], int m, int n) {

                   StringBuffer stringbuffer = new StringBuffer(2 * n);

                   int k = m + n;

                   for (int l = m; l < k; l++) {

                            appendHexPair(bytes[l], stringbuffer);

                   }

                   return stringbuffer.toString();

         }

         private static void appendHexPair(byte bt, StringBuffer stringbuffer) {

                   char c0 = hex[(bt & 0xf0) >> 4];

                   char c1 = hex[bt & 0xf];

                   stringbuffer.append(c0);

                   stringbuffer.append(c1);

         }

}

package com.kaige123.util;

import java.io.File;

import java.io.IOException;

/**

 * 测试类

 * @author 凯哥

 */

public class Test {

         public static void main(String[] args) throws IOException {

                   //得到字符串MD5

                   String md5str=MD5Util.getMD5String("凯哥是个胖子");

                   System.out.println(md5str);

                   //得到文件的MD5

                   String filemd5str=MD5Util.getFileMD5String(new File("c:/kaige/a.txt"));

                   System.out.println(filemd5str);

         }

}