1 加密方法：

1.1 java自带jar工具MessageDigest实现

java.security.MessageDigest

public class MD5Utils {

    public static String stringToMD5(String plainText) {

        byte[] secretBytes = null;

        try {

            secretBytes = MessageDigest.getInstance("md5").digest(

                    plainText.getBytes());

        } catch (NoSuchAlgorithmException e) {

            throw new RuntimeException("没有这个md5算法！");

        }

        String md5code = new BigInteger(1, secretBytes).toString(16);

        for (int i = 0; i < 32 - md5code.length(); i++) {

            md5code = "0" + md5code;

        }

        return md5code;

    }

}

1.2 spring自带的工具DigestUtils实现

org.springframework.util.DigestUtils

DigestUtils.md5DigestAsHex("1234".getBytes())

2 使用方法：

@Test

public void testMd5() throws NoSuchAlgorithmException{

    MessageDigest md = MessageDigest.getInstance("MD5");

    // java自带工具包MessageDigest  

    String resultString = MD5Utils.md5("123456");

    System.out.println(resultString);

    // e10adc3949ba59abbe56e057f20f883e

    String resultString1 = MD5Utils.md5("1234");

    System.out.println(resultString1);

    //81dc9bdb52d04dc20036dbd8313ed055

    // spring自带工具包DigestUtils

    System.out.println(DigestUtils.md5DigestAsHex("1234".getBytes()));

    // 81dc9bdb52d04dc20036dbd8313ed055

}