Java实现MD5加密与解密

import java.security.MessageDigest;

/**
* MD5技术加密解密
*/
public class MD5Tools {

public static String bytesToHexString(byte[] src) {
StringBuilder stringBuilder = new StringBuilder("");
if (src == null || src.length <= 0) {
return null;
}
for (int i = 0; i < src.length; i++) {
int v = src[i] & 0xFF;
String hv = Integer.toHexString(v);
if (hv.length() < 2) {
stringBuilder.append(0);
}
stringBuilder.append(hv);
}
return stringBuilder.toString();
}

/**
* 解析
* @param hexString
* @return
*/
public static byte[] hexStringToBytes(String hexString) {
if (hexString == null || hexString.equals("")) {
return null;
}
hexString = hexString.toUpperCase();
int length = hexString.length() / 2;
char[] hexChars = hexString.toCharArray();
byte[] d = new byte[length];
for (int i = 0; i < length; i++) {
int pos = i * 2;
d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
}
return d;
}

/**
* 将指定byte数组以16进制的形式打印到控制台
* @param b
*/
public static void printHexString(byte[] b) {
for (int i = 0; i < b.length; i++) {
String hex = Integer.toHexString(b[i] & 0xFF);
if (hex.length() == 1) {
hex = '0' + hex;
}
System.out.print(hex.toUpperCase());
}

}

/**
* Convert char to byte
* @param c char
* @return byte
*/
private static byte charToByte(char c) {
return (byte) "0123456789abcdef".indexOf(c);
}

/**
* 加密
* @param str
* @return
*/
public static String encode(String str) {
String strDigest = "";
try {
// 此 MessageDigest 类为应用程序提供信息摘要算法的功能，必须用try,catch捕获
MessageDigest md5 = MessageDigest.getInstance("MD5");

byte[] data;
data = md5.digest(str.getBytes("utf-8"));// 转换为MD5码
strDigest = bytesToHexString(data);
} catch (Exception ex) {
throw new RuntimeException(ex);
}
return strDigest;
}

}