/*
 * Copyright 2015-2016 RonCoo(http://www.roncoo.com) Group.
 *  
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.roncoo.jui.common.util;

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

/**
 * MD5加密，使用UTF-8编码
 *
 * @author wujing
 */
public final class MD5Util {

	private MD5Util() {
	}

	/**
	 * Used building output as Hex
	 */
	private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

	/**
	 * 对字符串进行MD5加密， 默认使用UTF-8
	 * 
	 * @param text
	 *            明文
	 * @return 密文
	 */
	public static String MD5(String text) {
		return MD5(text, "UTF-8");
	}

	/**
	 * 对字符串进行MD5加密
	 * 
	 * @param text
	 *            明文
	 * @param charsetName
	 *            指定编码
	 * @return 密文
	 */
	public static String MD5(String text, String charsetName) {
		MessageDigest msgDigest = null;
		try {
			msgDigest = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException e) {
			throw new IllegalStateException("System doesn't support MD5 algorithm.");
		}
		try {
			msgDigest.update(text.getBytes(charsetName)); // 注意是按照指定编码形式签名
		} catch (UnsupportedEncodingException e) {
			throw new IllegalStateException("System doesn't support your  EncodingException.");
		}
		byte[] bytes = msgDigest.digest();
		return new String(encodeHex(bytes));
	}

	private static char[] encodeHex(byte[] data) {
		int l = data.length;
		char[] out = new char[l << 1];
		for (int i = 0, j = 0; i < l; i++) {
			out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
			out[j++] = DIGITS[0x0F & data[i]];
		}
		return out;
	}

}
