Java中MessageDigest来实现数据加密的方法

package com.company;

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

public class MessageDigestTest {

  public static void main(String[] args) throws NoSuchAlgorithmException {

    String source = "123123";
    String md5Str = getMd5(source);


    System.out.println(md5Str);

  }

  /**
   * 通过md5进行加密
   * @param source 要加密的数据
   * @return
   * @throws NoSuchAlgorithmException
   */
  private static String getMd5(String source) throws NoSuchAlgorithmException {
    //1.获取MessageDigest对象
    MessageDigest digest = MessageDigest.getInstance("md5");

    //2.执行加密操作
    byte[] bytes = source.getBytes();

    //在MD5算法这，得到的目标字节数组的特点：长度固定为16
    byte[] targetBytes = digest.digest(bytes);

    //3.声明字符数组
    char [] characters = new char[]{'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

    //4.遍历targetBytes
    StringBuilder builder = new StringBuilder();
    for (byte b : targetBytes) {
      //5.取出b的高四位的值
      //先把高四位通过右移操作拽到低四位
      int high = (b >> 4) & 15;

      //6.取出b的低四位的值
      int low = b & 15;

      //7.以high为下标从characters中取出对应的十六进制字符
      char highChar = characters[high];

      //8.以low为下标从characters中取出对应的十六进制字符
      char lowChar = characters[low];

      builder.append(highChar).append(lowChar);
    }

    return builder.toString();
  }
}

package com.company;

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

public class MD5Tool {
  private static ThreadLocal<MD5Tool> md5ToolThreadLocal = new ThreadLocal<>();

  private MD5Tool() {
  }

  /**
   * 获取一个MD5工具实例
   */
  public static MD5Tool getInstance() {
    if (md5ToolThreadLocal.get() == null) {
      md5ToolThreadLocal.set(new MD5Tool());
    }
    return md5ToolThreadLocal.get();
  }

  /**
   * 通过md5进行加密
   *
   * @param source 要加密的数据
   * @return
   * @throws NoSuchAlgorithmException
   */
  public String getMd5(String source) throws NoSuchAlgorithmException {
    //1.获取MessageDigest对象
    MessageDigest digest = MessageDigest.getInstance("md5");

    //2.执行加密操作
    byte[] bytes = source.getBytes();

    //在MD5算法这，得到的目标字节数组的特点：长度固定为16
    byte[] targetBytes = digest.digest(bytes);

    //3.声明字符数组
    char[] characters = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    //4.遍历targetBytes
    StringBuilder builder = new StringBuilder();
    for (byte b : targetBytes) {
      //5.取出b的高四位的值
      //先把高四位通过右移操作拽到低四位
      int high = (b >> 4) & 15;

      //6.取出b的低四位的值
      int low = b & 15;

      //7.以high为下标从characters中取出对应的十六进制字符
      char highChar = characters[high];

      //8.以low为下标从characters中取出对应的十六进制字符
      char lowChar = characters[low];

      builder.append(highChar).append(lowChar);
    }

    return builder.toString();
  }

}