suneel reddy

Mar 25th, 2005

How do I have the JSP-generated servlet subclass my own custom servlet class, instead of the default? One should be very careful when having JSP pages extend custom servlet classes as opposed to the default one generated by the JSP engine. In doing so, you may lose out on any advanced optimization that may be provided by the JSPengine. In any case, your new superclass has to fulfill the contract with the JSPngine by: Implementing the HttpJspPage interface, if the protocol used is HTTP, or implementing JspPage otherwise Ensuring that all the methods in the Servlet interface are declared final Additionally, your servlet superclass also needs to do the following:The service() method has to invoke the _jspService() methodThe init() method has to invoke the jspInit() methodThe destroy() method has to invoke jspDestroy()If any of the above conditions are not satisfied, the JSP engine may throw a translation error. Once the superclass has been developed, you can have your JSP extend it as follows:<%@ page extends="packageName.ServletName" %<

Can I stop JSP execution while in the midst of processing a request?

Yes. Preemptive termination of request processing on an error condition is a good way to maximize the throughput of a high-volume JSP engine. The trick (asuming Java is your scripting language) is to use the return statement when you want to terminate further processing. For example, consider:<% if (request.getParameter("foo") != null) {// generate some html or update bean property} else {/* output some error message or provide redirection back to the input form after creating a memento bean updated with the 'valid' form elements that were input. This bean can now be used by the previous form to initialize the input elements that were valid then, return from the body of the _jspService() method to terminate further processing */return;}%>