Java读取文件MD5的两种方案

最近要弄一下Java读取文件MD5，注意这里是小文件，网上找了一下，有两种解决方案，一种是用MessageDigest来实现，另种是用org.apache.commons.codec.digest来实现，代码如下：

 package cdm;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.math.BigInteger;
 import java.nio.MappedByteBuffer;
 import java.nio.channels.FileChannel;
 import java.security.MessageDigest;

 import org.apache.commons.codec.digest.*;
 import org.apache.commons.io.IOUtils;

 public class testMD5 {

      public static String getMd5ByFile(File file) throws FileNotFoundException {
             String value = null;
             FileInputStream in = new FileInputStream(file);
         try {
             MappedByteBuffer byteBuffer = in.getChannel().map(FileChannel.MapMode.READ_ONLY, 0, file.length());
             MessageDigest md5 = MessageDigest.getInstance("MD5");
             md5.update(byteBuffer);
             BigInteger bi = new BigInteger(1, md5.digest());
             value = bi.toString(16);
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
                 if(null != in) {
                     try {
                     in.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
         }
         return value;
         }

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

         String path="E:\\commons-codec-1.9-bin.zip";

         String v = getMd5ByFile(new File(path));
         System.out.println("MD5:"+v.toUpperCase());

         FileInputStream fis= new FileInputStream(path);
         String md5 = DigestUtils.md5Hex(IOUtils.toByteArray(fis));
         IOUtils.closeQuietly(fis);
         System.out.println("MD5:"+md5);

         //System.out.println("MD5:"+DigestUtils.md5Hex("WANGQIUYUN"));
     }

 }

运行：

结果在官网提供的MD5一致。

附commons-codec-1.9.jar下载地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi

如果要处理过G的文件，请参照：http://www.cnblogs.com/yaowukonga/p/3523668.html