加密：DigestUtils与java MessageDigest

public class StringUtilTest {

static final String TARGET = "changeme";

/*
* 不可逆算法  MD5
*/
@Test
public void Md5()
{
String str = DigestUtils.md5DigestAsHex(TARGET.getBytes());
System.out.println("md5Hex:     "+str);
}
}

public class UtilTest {

static final String TARGET = "changeme";

/*
* 不可逆算法  MD5
*/
@Test
public void Md5()
{
String str = DigestUtils.md5Hex(TARGET);
System.out.println("md5Hex:     "+str);
}
/*
* 不可逆算法  SHA1
*/
@Test
public void Sha1()
{
String str = DigestUtils.shaHex(TARGET);
print("shaHex:     "+str);
str = DigestUtils.sha256Hex(TARGET);
print("sha256Hex:  "+str);
str = DigestUtils.sha384Hex(TARGET);
print("sha384Hex:  "+str);
str = DigestUtils.sha512Hex(TARGET);
print("sha512Hex:  "+str);
}

/*
* 可逆算法  BASE64
*/

@Test
public void Base64()
{
//加密
byte[] b = Base64.encodeBase64(TARGET.getBytes(), true);
String str = new String(b);
print("BASE64:     "+str);

//解密
byte[] b1 = Base64.decodeBase64(str);
print("解密之后内容为：  "+new String(b1));
}
public void print(Object obj)
{
System.out.println(obj);
}
}

@Test
public void test()
{
try
{
String password = "12345psw";

//MD5表示加密算法，可以选择其他参数，如SHA-1等
MessageDigest digest = MessageDigest.getInstance("MD5");
//先调用update，再调动digest
digest.update(password.getBytes());
byte[] byteResult = digest.digest();

//因为加密完为字节数组，需要转化为字符串
String result = convertbyte2String(byteResult);

System.out.println(result);
}
catch (NoSuchAlgorithmException e)
{
e.printStackTrace();
}

}

//将字节数组转化为字符串
private String convertbyte2String(byte[] byteResult)
{
char[] hexDigits = {'0','1','2','3','4','5','6','7','8','9', 'A','B','C','D','E','F' };

//4位代表一个16进制，所以长度需要变为原来2倍
char[] result = new char[byteResult.length*2];

int index = 0;
for(byte b:byteResult)
{
//先转换高4位
result[index++] = hexDigits[(b>>>4)& 0xf];
result[index++] = hexDigits[b& 0xf];
}
return new String(result);
}