Java throws clause - sonarqube issue

I have kind of old code where we run sonarqube. I am not expert on Java and Exception descendants etc. so I hope someone will be able to help me to fix this issue, as Sonar says it is a blocker.

This is the code:

package xxx;
import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;
public class Encryptor {
private static final String ALGORITHM = "AES";
private static final String defaultSecretKey = "xxx";
private Key secretKeySpec;
public Encryptor() throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException,
UnsupportedEncodingException {
this(null);
}
public Encryptor(String secretKey) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
UnsupportedEncodingException {
this.secretKeySpec = generateKey(secretKey);
}
public String encrypt(String plainText) throws InvalidKeyException, NoSuchAlgorithmException,
NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
byte[] encrypted = cipher.doFinal(plainText.getBytes("UTF-8"));
return asHexString(encrypted);
}
public String decrypt(String encryptedString) throws InvalidKeyException, IllegalBlockSizeException,
BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
byte[] original = cipher.doFinal(toByteArray(encryptedString));
return new String(original);
}
private Key generateKey(String secretKey) throws UnsupportedEncodingException, NoSuchAlgorithmException {
if (secretKey == null) {
secretKey = defaultSecretKey;
}
byte[] key = (secretKey).getBytes("UTF-8");
MessageDigest sha = MessageDigest.getInstance("SHA-256");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only the first 128 bit
KeyGenerator kgen = KeyGenerator.getInstance("AES");
kgen.init(256); // 192 and 256 bits may not be available
return new SecretKeySpec(key, ALGORITHM);
}
private final String asHexString(byte buf[]) {
StringBuffer strbuf = new StringBuffer(buf.length * 2);
int i;
for (i = 0; i < buf.length; i++) {
if (((int) buf[i] & 0xff) < 0x10) {
strbuf.append("0");
}
strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
}
return strbuf.toString();
}
private final byte[] toByteArray(String hexString) {
int arrLength = hexString.length() >> 1;
byte buf[] = new byte[arrLength];
for (int ii = 0; ii < arrLength; ii++) {
int index = ii << 1;
String l_digit = hexString.substring(index, index + 2);
buf[ii] = (byte) Integer.parseInt(l_digit, 16);
}
return buf;
}
public static void main(String[] args) throws Exception {
if (args.length == 1) {
String plainText = args[0];
Encryptor aes = new Encryptor();
String encryptedString = aes.encrypt(plainText);
//this line only ensures that decryption works
String decryptedString = aes.decrypt(encryptedString);
System.out.println("Original Password: " + plainText + " and Encrypted Password: " + encryptedString);
} else {
System.out.println("USAGE: java AES string-to-encrypt");
}
}
}

And problem is on this line:

public static void main(String[] args) throws Exception {

Sonar says Remove this throws clause

Does anybody know how to fix this or why is this happening?

Thanks a lot.

M.

Thanks to all comments:

This is solution (removal of generic exception and adding explicit exceptions):

public static void main(String[] args) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, UnsupportedEncodingException, IllegalBlockSizeException, BadPaddingException {

It is always a good apprach to use the least common denominator, or more specific, the exception class that provides the best abstraction over all of its descendents.

Consider the following method declaration:

public String encrypt(String plainText) 
throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException,
UnsupportedEncodingException, IllegalBlockSizeException, BadPaddingException,
UnsupportedEncodingException  {
// body
}

A closer inspection of all those exceptions reveals that all of them extend GeneralSecurityException. Therefore, you can refactor the above code as:

public String encrypt(String plainText) throws GeneralSecurityException,
UnsupportedEncodingException  {
// body
}

The only exception, which does not inherit GeneralSecurityException, is UnsupportedEncodingException so you have to explicitly declare it.

Think of it from the client side: Which version would you rather use?

try {
String encrypted = cipher.encrypt("Test");
} catch(InvalidKeyException | NoSuchAlgorithmException | NoSuchPaddingException
| UnsupportedEncodingException | IllegalBlockSizeException | BadPaddingException e) {
// cannot encrypt
} catch(UnsupportedEncodingException e) {
// wrong encoding
}

try {
String encrypted = cipher.encrypt("Test");
} catch(GeneralSecurityException e) {
// cannot encrypt
} catch(UnsupportedEncodingException e) {
// wrong encoding
}