md5加密

package com.horizon.util;

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

/**
 * 将字符串进行md5加密
 * @author LIMENGCHENG292
 *
 */
public class MD5 {
	/**
	 * 
	 * @param str 需要被加密的String
	 * @return 加密之后的String   (32个16进制数 128位) 
	 * 			例如：A1234567890B1234567890C123456789
	 * @throws NoSuchAlgorithmException
	 */
	private static final String DEFAULTMD5String = "00000000000000000000000000000000";
	public static String MD5Encoder(String str) 
			throws NoSuchAlgorithmException {
		MessageDigest md5 = MessageDigest.getInstance("MD5");
		if (str == null) {
			// 如果需要加密的String是null，返回默认的DEFAULTMD5String
			return DEFAULTMD5String;
		}
		md5.update(str.getBytes());
		byte[] b = md5.digest();
		int i = 0;
		StringBuffer buf = new StringBuffer("");
		for (int offset=0; offset<b.length; offset++) {
			i = b[offset];
			if (i<0) {
				i = i + 256;
			}				
			if (i<16) {
				buf.append("0");
			}
			buf.append(Integer.toHexString(i));
		}
		return buf.toString();
	}
	
	public static String MD5Encoder(Object obj) 
			throws NoSuchAlgorithmException, IOException {
		MessageDigest md5 = MessageDigest.getInstance("MD5");
		if (obj == null) {
			// 如果需要加密的Object是null，返回默认的DEFAULTMD5String
			return DEFAULTMD5String;
		}
		md5.update(DataUtil.objToBytes(obj));
		byte[] b = md5.digest();
		int i = 0;
		StringBuffer buf = new StringBuffer("");
		for (int offset=0; offset<b.length; offset++) {
			i = b[offset];
			if (i<0) {
				i = i + 256;
			}				
			if (i<16) {
				buf.append("0");
			}
			buf.append(Integer.toHexString(i));
		}
		return buf.toString();
	}
}

第二个方法中的参数obj,必须是可序列化的,否则会throw一个NotSerializableException
上类中用到的DataUtil类,代码如下

package com.horizon.util;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class DataUtil {

	public static byte[] objToBytes(Object obj) throws IOException {
		if (obj == null) {
			return null;
		}
		ByteArrayOutputStream bo = null;
		ObjectOutputStream oo = null;
		try {
			bo = new ByteArrayOutputStream();
			oo = new ObjectOutputStream(bo);
			oo.writeObject(obj);
			oo.flush();
			oo.close();
			return bo.toByteArray();
		} catch (IOException e) {
			throw e;
		} finally {
			if (bo != null) {
				bo.close();
				bo = null;
			}
		}
	}
}