MD5加密

    /**
    * MD5 加密
    *@parma
   *str-需要加密的字符串
    *@return
    *密文
    */ 
   public String getMD5Str(String str) { 
       MessageDigest messageDigest = null; 

       try { 
           messageDigest = MessageDigest.getInstance("MD5"); 

           messageDigest.reset(); 

           messageDigest.update(str.getBytes("UTF-8")); 
       } catch (NoSuchAlgorithmException e) { 
           System.out.println("NoSuchAlgorithmException caught!"); 
           System.exit(-1); 
       } catch (UnsupportedEncodingException e) { 
           e.printStackTrace(); 
       } 

       byte[] byteArray = messageDigest.digest(); 

       StringBuffer md5StrBuff = new StringBuffer(); 

       for (int i = 0; i < byteArray.length; i++) {             
           if (Integer.toHexString(0xFF & byteArray[i]).length() == 1) 
               md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i])); 
           else 
               md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i])); 
       } 

       return md5StrBuff.toString(); 
   }