What does the JSP engine do when presented with a JavaServer Page to process?
The JSP engine builds a servlet. The HTML portions of the JavaServer Page become Strings transmitted to print methods of a PrintWriter object. The JSP tag portions result in calls to methods of the appropriate JavaBean class whose output is translated into more calls to a println method to place the result in the HTML document
Explain the directory structure of a web application.
The directory structure of a web application consists of two parts.
A private directory called WEB-INF
A public resource directory which contains public resource folder.
WEB-INF folder consists of
1. web.xml
2. classes directory
3. lib directory
What is the difference b/w variable declared inside a declaration part and variable declared in scriplet part?
Variable declared inside declaration part is treated as a global variable.that means after convertion jsp file into servlet that variable will be in outside of service method or it will be declared as instance variable.And the scope is available to complete jsp and to complete in the converted servlet class.where as if u declare a variable inside a scriplet that variable will be declared inside a service method and the scope is with in the service method.
What is better approach for enabling thread-safe servlets and JSPs? SingleThreadModel Interface or Synchronization?
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.
How does JSP handle run-time exceptions?
One can use the errorPage attribute of the page directive to have uncaught run-time exceptions automatically forwarded to an error processing page.
For example: <%@ page errorPAge="error.jsp" %>
redirects the browser to the JSP page error.jsp if an uncaught exception is encountered during request processing. Within error.jsp, if you indicate that it is an error-processing page, via the directive:<%@ page iserrorPage="true"%>
Throwable object describing the exception may be accessed within the error page via the exception implicit object. Note: You must always use a relative URL as the value for the errorPage attribute.