Java Enterprise Best Practices

Capture Enough Information to Fine-Tune the Application

With a common error handler for both servlets and JSP pages, it’s easy to log information about runtime errors. By capturing information detailing where the error occurred, the precise problem, and all (or at least most of) the dynamic data available at the time, you can fine-tune the application to deal more gracefully with common, predictable runtime errors.

A global error handler declared with the <error-page> element in the web.xml file has access to all information of interest. First of all, it can get information about which component failed and the exception that was thrown through the following request attributes.

Request attribute name	Java type	Description
javax.servlet.error.status_code	Integer	The HTTP status code that triggered a handler declared as a status code handler
javax.servlet.error.exception	Throwable	The exception that triggered a handler declared as an exception handler
javax.servlet.error.request_uri	String	The URL for the request that triggered the handler
javax.servlet.error.servlet_name	String	The declared name for the servlet or JSP page that triggered the handler, or the class name if no name is declared

In addition to the information available through these request attributes, you should also consider logging request parameter values and application-dependent request, session, and context attributes.