readme.md

Code Smell 26 - Exceptions Polluting

It is very nice to have lots of different exceptions. Your code is declarative and robust. Or not?

TL;DR: Don't create anemic and empty objects. Even if they are Exceptions.

Problems

• Over Design

• Namespace Pollution

• Empty Classes

Solutions

1. Avoid creating anemic exceptions as globals.

2. Create exceptions only if they behave differently.

3. Model exceptions with objects. Classes are handy for lazy programmers.

4. Remove Unhandled Exceptions

Sample Code

Wrong

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class FileReader {

    public static void main(String[] args) {
        FileReader file = null;

        try {
            file = new FileReader("source.txt");
            file.read();
        }
        catch(FileNotFoundException e) {
            e.printStackTrace();
        }
        catch(FileLockedException e) {
            e.printStackTrace();
        }
        catch(FilePermissionsException e) {
            e.printStackTrace();
        }
        catch(IOException e) {
            e.printStackTrace();
        }
        finally {
            try {
                file.close();
            }
            catch(IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Right

public class FileReader {

    public static void main(String[] args) {
        FileReader file = null;

        try {
            file = new FileReader("source.txt");
            file.read();
        }
        catch(FileException exception) {
            if (exception.description == 
                (this.expectedMessages()
                 .errorDescriptionFileTemporaryLocked(){
                // sleep and retry
                // IF behavior is the same with all the exceptions
                // just change the text on 
                // object creation and raise the correct instance
            }            
            this.showErrorToUser(exception.messageToUser();
             // This example is simplified. 
             // You should translate the text
        }                
        finally {
            try {
                file.close();
             } catch (IOException ioException) {
                ioException.printStackTrace();
             }
        }
    }
}

Detection

New exceptions should override behavior methods.

No. code, description, resumable, etc. are not behavioral.

Tags

• Abuser

• Naming

Conclusion

You would not create different classes for every Person instance, so they return different names. Why would you do it with exceptions.

How often do you catch a specific exception?.

Go out and check your code.

Is it necessary to be a class?

You are already coupled to the class. Couple to the description instead.

Exception instances should NOT be Singletons.

Relations

Code Smell 01 - Anemic Models

Code Smell 114 - Empty Class

Credits

Photo by Nick van den Berg on Unsplash

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You will fall to ruin because you believe that exceptions to the rule make new rules.

Pierce Brown

Software Engineering Great Quotes

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This article is part of the CodeSmell Series.

How to Find the Stinky Parts of your Code