import java.security.MessageDigest;

public class PasswordEncoder {

 private final static String[] hexDigits = { "0", "1", "2", "3", "4", "5",

   "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

 private Object salt;

 private String algorithm;

 public PasswordEncoder(Object salt, String algorithm) {

  this.salt = salt;

  this.algorithm = algorithm;

 }

 public String encode(String rawPass) {

  String result = null;

  try {

   MessageDigest md = MessageDigest.getInstance(algorithm);

   //加密后的字符串

   result = byteArrayToHexString(md.digest(mergePasswordAndSalt(rawPass).getBytes("utf-8")));

  } catch (Exception ex) {

  }

  return result;

 }

    public boolean isPasswordValid(String encPass, String rawPass) {

        String pass1 = "" + encPass;

        String pass2 = encode(rawPass);

        return pass1.equals(pass2);

    }

    private String mergePasswordAndSalt(String password) {

        if (password == null) {

            password = "";

        }

        if ((salt == null) || "".equals(salt)) {

            return password;

        } else {

            return password + "{" + salt.toString() + "}";

        }

    }

 /**

  * 转换字节数组为16进制字串

  * @param b 字节数组

  * @return 16进制字串

  */

 private static String byteArrayToHexString(byte[] b) {

  StringBuffer resultSb = new StringBuffer();

  for (int i = 0; i < b.length; i++) {

   resultSb.append(byteToHexString(b[i]));

  }

  return resultSb.toString();

 }

 private static String byteToHexString(byte b) {

  int n = b;

  if (n < 0)

   n = 256 + n;

  int d1 = n / 16;

  int d2 = n % 16;

  return hexDigits[d1] + hexDigits[d2];

 }

    public static void main(String[] args) {

     String salt = "helloworld";

  PasswordEncoder encoderMd5 = new PasswordEncoder(salt, "MD5");

     String encode = encoderMd5.encode("test");

     System.out.println(encode);

     boolean passwordValid = encoderMd5.isPasswordValid("1bd98ed329aebc7b2f89424b5a38926e", "test");

     System.out.println(passwordValid);

     PasswordEncoder encoderSha = new PasswordEncoder(salt, "SHA");

     String pass2 = encoderSha.encode("test");

     System.out.println(pass2);

     boolean passwordValid2 = encoderSha.isPasswordValid("1bd98ed329aebc7b2f89424b5a38926e", "test");

     System.out.println(passwordValid2);

 }

}