Friday, March 13, 2009

How do I have the JSP-generated servlet subclass my own custom servlet

Question :How do I have the JSP-generated servlet subclass my own custom servlet

class, instead of the default? (JSP)




Answer :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 JSP engine. In any case, your new superclass has to fulfill

the contract with the JSP engine 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() method

The init() method has to invoke the jspInit() method

The 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" %<



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