Exception Handling in Web Applications

Error Handling is an important part of any implementation. An application without Error Handling is like a patient with all door closed for diagnosis. It is a perfect time killer for developers to debug the application issues without proper error handling. Hence it is an important topic to discuss. However here we are concentrating more on error handling in web applications (using JSP, Servlets).

Motive of error handling is to capture any error generated in the application, log it to any logging system and propagate it to right point so that it can be directed to the user with all useful information. So the basic flow of error handling should be

• Apply try-catch block with right exception type in catch around the code which may generate the error
• Log the error using any logging mechanism. One of the popular logging system is log4j using commons logging. Ensure to use right logging level i.e. debug, info, warn, error etc
• Apply business logic whatever is required to handle the erroneous case as per application requirement
• If error is not manageable and condition should be propagated to user, throw the appropriate error further after wrapping the original error. Make sure that new exception should carry all user centric details which can help them to understand the cause of error, and developer centric information which can help them to debug the issue. 
• As a general mechanism, error codes can be set to exception which can describes the reason of problem at Application and UI level. These error codes can also be used to show the localized messages on UI
• Application Framework should provide the facility to handle any exception originated from the application and redirect it to a designated UI which can show the error details to user with all the details
• The UI can also have the mechanism which can facilitate the user to log the issue directly in Issue Tracking system or to send email to the support staff with all the details