JDK自带方法实现消息摘要运算

啊，有点小注释，懒得介绍了，就贴个代码吧，大意理解就可以了。

 package jdbc.pro.lin;

 import java.security.InvalidKeyException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;

 import javax.crypto.KeyGenerator;
 import javax.crypto.Mac;
 import javax.crypto.SecretKey;
 import javax.crypto.spec.SecretKeySpec;

 import org.apache.commons.codec.binary.Base64;

 public class MyMessageDigest {
     public static final String PLAIN_TEXT = "i m a sample";
     public static final String MD_ALGORITHM = "MD5";
     public static final String SHA_ALGORITHM = "SHA-512";
     public static final String MAC_ALGORITHM = "HmacSHA512";

     public static void main(String[] args) {
         System.out.println("MD5: " + MD5(PLAIN_TEXT.getBytes()));
         System.out.println("SHA-512: " + SHA(PLAIN_TEXT.getBytes()));
         System.out.println("HmacSHA512：" + MAC(PLAIN_TEXT.getBytes()));
     }

     /**
      * 1.消息摘要算法，MD家族，有MD2 MD4 MD5，其中MD4 JDK不支持
      *
      * @param plainText
      * @return
      */
     public static String MD5(byte[] plainText) {
         MessageDigest messageDigest;
         try {
             messageDigest = MessageDigest.getInstance(MD_ALGORITHM);
             return Base64.encodeBase64String(messageDigest.digest(plainText));
         } catch (NoSuchAlgorithmException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return null;

     }

     /**
      * 2.SHA Security Hash Algorithm 安全散列算法，固定长度摘要信息 SHA-1 SHA-2( SHA-224
      * SHA-256 SHA-384 SHA-512) 使用的依然是MessageDigest类，JDK不支持224
      *
      * @param plainText
      * @return
      */
     public static String SHA(byte[] plainText) {
         MessageDigest messageDigest;
         try {
             messageDigest = MessageDigest.getInstance(SHA_ALGORITHM);
             return Base64.encodeBase64String(messageDigest.digest(plainText));
         } catch (Exception e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 3.MAC(Message Authentication Code) 消息认证码算法，是含有密钥散列函数算法。
      * 兼容了MD和SHA的特性。
      * 加密过程三步走，与后面要介绍的对称加密和非对称加密是相似的
      * 1) 传入算法，实例化一个加密器
      * 2) 传入密钥，初始化加密器
      * 3) 调用doFinal方法进行加密
      * @param plainText
      * @return
      */
     public static String MAC(byte[] plainText) {

         try {
             byte[] secretBytes = generatorMACSecretKey();
             SecretKey key = restoreMACSecretKey(secretBytes);
             Mac mac = Mac.getInstance(MAC_ALGORITHM);
             mac.init(key);
             return Base64.encodeBase64String(mac.doFinal(plainText));
         } catch (NoSuchAlgorithmException | InvalidKeyException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return null;

     }

     /**
      * MAC生成随机密钥 两步走 1.创建一个KeyGenerator 2.调用KeyGenerator.generateKey方法
      *
      * @return
      */
     public static byte[] generatorMACSecretKey() {
         KeyGenerator keyGenerator;
         try {
             keyGenerator = KeyGenerator.getInstance(MAC_ALGORITHM);
             SecretKey key = keyGenerator.generateKey();
             return key.getEncoded();
         } catch (NoSuchAlgorithmException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 还原密钥
      *
      * @param secretBytes
      * @return
      */
     public static SecretKey restoreMACSecretKey(byte[] secretBytes) {
         SecretKey key = new SecretKeySpec(secretBytes, MAC_ALGORITHM);
         return key;
     }
 }