MD5Utils.java

package xyz.yhsj.yhutils.secarity;

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

/**
 * 提取文件MD5值
 *
 */
public class MD5Utils {
	private static final char HEX_DIGITS[] = { '0', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	private static String toHexString(byte[] b) {
		StringBuilder sb = new StringBuilder(b.length * 2);
		for (int i = 0; i < b.length; i++) {
			sb.append(HEX_DIGITS[(b[i] & 0xf0) >>> 4]);
			sb.append(HEX_DIGITS[b[i] & 0x0f]);
		}
		return sb.toString();
	}

	/**
	 * 文件加密
	 * 
	 * @param filename
	 * @return
	 */
	public static String md5file(String filename) {
		InputStream fis;
		byte[] buffer = new byte[1024];
		int numRead = 0;
		MessageDigest md5;
		try {
			fis = new FileInputStream(filename);
			md5 = MessageDigest.getInstance("MD5");
			while ((numRead = fis.read(buffer)) > 0) {
				md5.update(buffer, 0, numRead);
			}
			fis.close();
			return toHexString(md5.digest());
		} catch (Exception e) {
			System.out.println("error");
			return null;
		}
	}

	/**
	 * 字符串加密
	 * 
	 * @param string
	 * @return
	 */
	public static String md5(String string) {
		byte[] hash;
		try {
			hash = MessageDigest.getInstance("MD5").digest(
					string.getBytes("UTF-8"));
		} catch (NoSuchAlgorithmException e) {
			throw new RuntimeException("Huh, MD5 should be supported?", e);
		} catch (UnsupportedEncodingException e) {
			throw new RuntimeException("Huh, UTF-8 should be supported?", e);
		}

		StringBuilder hex = new StringBuilder(hash.length * 2);
		for (byte b : hash) {
			if ((b & 0xFF) < 0x10)
				hex.append("0");
			hex.append(Integer.toHexString(b & 0xFF));
		}
		return hex.toString();
	}

}