Encrypt.java

package com.jqyd.app;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 利用MD5进行加密
 * 
 * @param str
 *            待加密的字符串
 * @return 加密后的字符串
 * @throws NoSuchAlgorithmException
 *             没有这种产生消息摘要的算法
 * @throws UnsupportedEncodingException
 */

public class Encrypt {

	public static String EncoderByMd5(String str) {
		StringBuffer buf = null;
		try {
			MessageDigest md = MessageDigest.getInstance("MD5");
			md.update(str.getBytes());
			byte b[] = md.digest();
			int i;
			buf = new StringBuffer("");
			for (int offset = 0; offset < b.length; offset++) {
				i = b[offset];
				if (i < 0)
					i += 256;
				if (i < 16)
					buf.append("0");
				buf.append(Integer.toHexString(i));
			}
			System.out.println("result: " + buf.toString());// 32位的加密
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return buf.toString();

	}

	// 可逆的加密算法
	public static String encryptmd5(String str) {
		char[] a = str.toCharArray();
		for (int i = 0; i < a.length; i++) {
			a[i] = (char) (a[i] ^ 'l');
		}
		String s = new String(a);
		System.out.println("pwd encryptmd5:::" + s);
		return s;
	}

	/**
	 * 判断用户密码是否正确
	 * 
	 * @param newpasswd
	 *            用户输入的密码
	 * @param oldpasswd
	 *            数据库中存储的密码－－用户密码的摘要
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws UnsupportedEncodingException
	 */
	public static boolean checkpassword(String newpasswd, String oldpasswd)
			throws NoSuchAlgorithmException, UnsupportedEncodingException {
		if (EncoderByMd5(newpasswd).equals(oldpasswd))
			return true;
		else
			return false;
	}
}