MD5加密

package com.aug3.sys.util;

import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.DigestInputStream;
import java.security.MessageDigest;

import org.apache.commons.lang.StringUtils;

/**
 * 
 * @author 
 * 
 */
public class MD5 {
    public static final int BUFFER_SIZE = 1024 * 200; //create md5 string according to first 200k data

    
    /**
     * 根据文件的前200k数据生成MD5字符串
     * @param is
     * @return
     */
    public static String getMD5Str(InputStream is) {
        DigestInputStream dis = null;
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            messageDigest.reset();
            dis = new DigestInputStream(is, messageDigest);
            dis.read(new byte[BUFFER_SIZE]);
            return new BigInteger(1, messageDigest.digest()).toString(16);
        } catch (Exception e) {
            return "";
        } finally {
            if (dis != null) {
                try {
                    dis.close();
                } catch (IOException e) {
                }
            }
        }
    }
    
    /**
     * 根据文件的全部数据生成MD5字符串
     * @param is
     * @return
     */
    public static String getMD5Str(InputStream is, byte[] bytes) {
        DigestInputStream dis = null;
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            messageDigest.reset();
            dis = new DigestInputStream(is, messageDigest);
            dis.read(bytes);
            return new BigInteger(1, messageDigest.digest()).toString(16);
        } catch (Exception e) {
            return "";
        } finally {
            if (dis != null) {
                try {
                    dis.close();
                } catch (IOException e) {
                }
            }
        }
    }
    
    public static String md5(String str) {
        String result = null;

        if (!StringUtils.isBlank(str)) {
            try {
                MessageDigest md5 = MessageDigest.getInstance("MD5");
                md5.update(str.getBytes(), 0, str.length());
                result = String
                        .format("%032X", new BigInteger(1, md5.digest()));
            } catch (Exception e) {

            }
        }

        return result;
    }
    

}