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Technical Java Sample Questions : JSP Sample Questions

These questions would help the student study for his exam. Please note, as the study material for JSP and J2EE are different, there is a difference between the J2EE sample questions and JSP sample questions.

  1. How does JSP handle run-time exceptions?

    Answer: You can use the errorPage attribute of the page directive to have uncaught run-time exceptions automatically forwarded to an error processing page.

  2. How can I implement a thread-safe JSP page? What are the advantages and Disadvantages of using it?

    Answer: You can make your JSPs thread-safe by having them implement the SingleThreadModel interface.This is done by adding the directive ‹%@ page isThreadSafe="false" %› within your JSP page.With this, instead of a single instance of the servlet generated for your JSP page loaded in memory, you will have N instances of the servlet loaded and initialized, with the service method of each instance effectively synchronized.You can typically control the number of instances (N) that are instantiated for all servlets implementing SingleThreadModel through the admin screen for your JSP engine.More importantly, avoid using the tag for variables.If you do use this tag, then you should set isThreadSafe to true, as mentioned above.Otherwise, all requests to that page will access those variables, causing a nasty race condition.SingleThreadModel is not recommended for normal use.There are many pitfalls, including the example above of not being able to use ‹%! %›.You should try really hard to make them thread-safe the old fashioned way: by making them thread-safe.

  3. How do I use a scriptlet to initialize a newly instantiated bean?

    Answer: A jsp:useBean action may optionally have a body.If the body is specified, its contents will be automatically invoked when the specified bean is instantiated.Typically, the body will contain scriptlets or jsp:setProperty tags to initialize the newly instantiated bean, although you are not restricted to using those alone.

  4. How can I prevent the word "null" from appearing in my HTML input text fields when I populate them with a resultset that has null values?

    Answer: You could make a simple wrapper function, like
    ‹%!String blanknull(String s) {return (s == null) ? \"\" : s;}%›
    then use it inside your JSP form, like
    ‹input type="text" name="lastName" value="‹%=blanknull(lastName)% ›" ›

  5. What's a better approach for enabling thread-safe servlets and JSPs? SingleThreadModel Interface or Synchronization?

    Answer: Although the SingleThreadModel technique is easy to use, and works well for low volume sites, it does not scale well.If you anticipate your users to increase in the future, you may be better off implementing explicit synchronization for your shared data.The key however, is to effectively minimize the amount of code that is synchronzied so that you take maximum advantage of multithreading.Also, note that SingleThreadModel is pretty resource intensive from the server\'s perspective.The most serious issue however is when the number of concurrent requests exhaust the servlet instance pool.In that case, all the unserviced requests are queued until something becomes free - which results in poor performance.Since the usage is non-deterministic, it may not help much even if you did add more memory and increased the size of the instance pool.

These sample questions and answers may sound similar but are also different from EJB Sample Questions. For further reference, we have also provided Java Web Development Sample Questions and answers. The student can refer to them to score good marks in his / her exam.

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