Java - handle multiple exceptions in a method

Question

I am developing a public API for use by people in my applications. I'm currently trying to find a better way to handle exceptions. For example, the following code fragment generates four different types of exceptions:

Signature s = Signature.getInstance("SHA1withRSA"); //NoSuchAlgorithmException
s.initSign(keyChain.getPrivateKey());               //InvalidKeyException
s.update(plainText.getBytes("UTF-8"));              //UnsupportedEncodingException
byte[] signature = s.sign();                        //SignatureException
String signedData = base64Encoder.encode(signature);

My question is: how can I deal with them in the best way?

One of the ways I came across included exceptions and throwing special exceptions:

public void signRequest(Request request) throws APISignatureException {
    try {
        ...
        Signature s = Signature.getInstance("SHA1withRSA"); //NoSuchAlgorithmException
        s.initSign(keyChain.getPrivateKey());               //InvalidKeyException
        s.update(plainText.getBytes("UTF-8"));              //UnsupportedEncodingException
        byte[] signature = s.sign();                        //SignatureException
        String signedData = base64Encoder.encode(signature);
        ...
    }
    catch (Exception e) {
        throw new APISignatureException("Failed to create signature", e);
    }
}

Is this a good way to handle exceptions for an open API?

Answer 1

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Answer 2

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(Java 7):

public void signRequest(Request request) throws APISignatureException {
    try {
        Signature s = Signature.getInstance("SHA1withRSA"); //NoSuchAlgorithmException
        s.initSign(keyChain.getPrivateKey());               //InvalidKeyException
        s.update(plainText.getBytes("UTF-8"));              //UnsupportedEncodingException
        byte[] signature = s.sign();                        //SignatureException
        String signedData = base64Encoder.encode(signature);
    }
    catch (NoSuchAlgorithmException | InvalidKeyException | UnsupportedEncodingException | SignatureException e) {
        throw new APISignatureException("Failed to create signature", e);
    }
}

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public void signRequest(Request request) {
    try {
        Signature s = Signature.getInstance("SHA1withRSA"); //NoSuchAlgorithmException
        s.initSign(keyChain.getPrivateKey());               //InvalidKeyException
        s.update(plainText.getBytes("UTF-8"));              //UnsupportedEncodingException
        byte[] signature = s.sign();                        //SignatureException
        String signedData = base64Encoder.encode(signature);
    }
    catch (NoSuchAlgorithmException | InvalidKeyException | UnsupportedEncodingException | SignatureException e) {
        throw new RuntimeException("Failed to create signature", e); // This doesn't need to be explicitly caught
    }
}

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Answer 3

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Answer 4

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Answer 5

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 catch (APISignatureException|SignatureException e) {
    throw e;
 }

catch (APISignatureException e) {
    throw e;
}
catch (SignatureException e) {
    throw e;
}

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Answer 6

catch (Exception e) { APISignatureException.

, , :

public void signRequest(Request request) throws APISignatureException {
try {
    ...
    Signature s = Signature.getInstance("SHA1withRSA"); //NoSuchAlgorithmException
    s.initSign(keyChain.getPrivateKey());               //InvalidKeyException
    s.update(plainText.getBytes("UTF-8"));              //UnsupportedEncodingException
    byte[] signature = s.sign();                        //SignatureException
    String signedData = base64Encoder.encode(signature);
    ...
}
catch (APISignatureException e) {
     //Handle exception
}
catch (InvalidKeyException e) {
     //Handle exception
}

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catch (APISignatureException|InvalidKeyException e) {
    // Handle exception

}

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class APISignatureException extends Exception {
  // empty constructor
  public APISignatureException () {}

  //constructor that takes a string message
  public APISignatureException (String message)
  {
      super(message);
  }

}

. Exception

Answer 7

this, , .

try { 
   //Something that can throw an exception.
} catch (Exception e) {
  // To do whatever when the exception is caught.
} 

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try { 
   //Something that can throw an exception.
} catch (Exception e) {
  // To do whatever when the exception is caught & the returned.
} finally {
  // This will always execute if there is an exception or no exception.
}

().

InputMismatchException - Integer NoSuchElementException -
IllegalStateException -

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try { 
   rows=scan.nextInt();
} catch (InputMismatchException e) {
  // When the InputMismatchException is caught.
  System.out.println("The next token does not match the Integer regular expression, or is out of range");
} catch (NoSuchElementException e) {
  // When the NoSuchElementException is caught.
  System.out.println("Input is exhausted");
} catch (IllegalStateException e) {
  // When the IllegalStateException is caught.
  System.out.println("Scanner is close");
} 

Answer 8

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API , API, API. :

public class APIException { ...
}

public class APISignatureException extends APIException { ...
}

public class APISomeException extends APIException { ...
}