Java Server Pages (JSP) Interview Questions And Answers - DoAnswers.com

JavaServer Pages (JSP) technology enables Web developers and designers to rapidly develop and easily maintain, information-rich, dynamic Web pages that leverage existing business systems. As part of the Java technology family, JSP technology enables rapid development of Web-based applications that are platform independent. JSP technology separates the user interface from content generation, enabling designers to change the overall page layout without altering the underlying dynamic content.

Benefits for Developers

If you are a Web page developer or designer who is familiar with HTML, you can:

Use JSP technology without having to learn the Java language: You can use JSP technology without learning how to write Java scriplets. Although scriptlets are no longer required to generate dynamic content, they are still supported to provide backward compatibility.

Extend the JSP language: Java tag library developers and designers can extend the JSP language with "simple tag handlers," which utilize a new, much simpler and cleaner, tag extension API. This spurs the growing number of pluggable, reusable tag libraries available, which in turn reduces the amount of code needed to write powerful Web applications.

Easily write and maintain pages: The JavaServer Pages Standard Tag Library (JSTL) expression language is now integrated into JSP technology and has been upgraded to support functions. The expression language can now be used instead of scriptlet expressions.

No problem! The useBean action specifies the beanName attribute, which can be used for indicating a serialized bean. For example: A couple of important points to note. Although you would have to name your serialized file "filename.ser", you only indicate "filename" as the value for the beanName attribute. Also, you will have to place your serialized file within the WEB-INF\jsp\beans directory for it to be located by the JSP engine.

Yes. However, unlike servlets, you are not required to implement HTTP-protocol specific methods like doGet() or doPost() within your JSP page. You can obtain the data for the FORM input elements via the request implicit object within a scriptlet or expression as: or

Yes, the JSP specification does support creation of XML documents. For simple XML generation, the XML tags may be included as static template portions of the JSP page. Dynamic generation of XML tags occurs through bean components or custom tags that generate XML output. See the white paper Developing XML Solutions with JavaServer Pages Technology (PDF) for details.

The JSP 2.0 specification describes a mapping between JSP pages and XML documents. The mapping enables the creation and manipulation of JSP pages using XML tools.

Yes, you can invoke the JSP error page and pass the exception object to it from within a servlet. The trick is to create a request dispatcher for the JSP error page, and pass the exception object as a javax.servlet.jsp.jspException request attribute. However, note that you can do this from only within controller servlets. If your servlet opens an OutputStream or PrintWriter, the JSP engine will throw the following translation error: java.lang.IllegalStateException: Cannot forward as OutputStream or Writer has already been obtained The following code snippet demonstrates the invocation of a JSP error page from within a controller servlet: protected void sendErrorRedirect(HttpServletRequest request, HttpServletResponse response, String errorPageURL, Throwable e) throws ServletException, IOException { request.setAttribute ("javax.servlet.jsp.jspException", e); getServletConfig().getServletContext(). getRequestDispatcher(errorPageURL).forward(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) { try { // do something } catch (Exception ex) { try { sendErrorRedirect(request,response,"/jsp/MyErrorPage.jsp",ex); } catch (Exception e) { e.printStackTrace(); } } }

Yes. Because your JSP is just a servlet method, you can just put (whereever necessary) a < % return; % >

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:

No. You are supposed to make use of only a JSPWriter object (given to you in the form of the implicit object out) for replying to clients. A JSPWriter can be viewed as a buffered version of the stream object returned by response.getWriter(), although from an implementational perspective, it is not. A page author can always disable the default buffering for any page using a page directive as:

10. Defines an object that receives requests from the client and sends them to any resource (such as a servlet, HTML file, or JSP file) on the server. The servlet container creates the RequestDispatcher object, which is used as a wrapper around a server resou

This interface is intended to wrap servlets, but a servlet container can create RequestDispatcher objects to wrap any type of resource. getRequestDispatcher public RequestDispatcher getRequestDispatcher(java.lang.String path) Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path. A RequestDispatcher object can be used to forward a request to the resource or to include the resource in a response. The resource can be dynamic or static. The pathname must begin with a "/" and is interpreted as relative to the current context root. Use getContext to obtain a RequestDispatcher for resources in foreign contexts. This method returns null if the ServletContext cannot return a RequestDispatcher. Parameters: path - a String specifying the pathname to the resource Returns: a RequestDispatcher object that acts as a wrapper for the resource at the specified path See Also: RequestDispatcher, getContext(java.lang.String) getNamedDispatcher public RequestDispatcher getNamedDispatcher(java.lang.String name) Returns a RequestDispatcher object that acts as a wrapper for the named servlet. Servlets (and JSP pages also) may be given names via server administration or via a web application deployment descriptor. A servlet instance can determine its name using ServletConfig.getServletName(). This method returns null if the ServletContext cannot return a RequestDispatcher for any reason. Parameters: name - a String specifying the name of a servlet to wrap Returns: a RequestDispatcher object that acts as a wrapper for the named servlet See Also: RequestDispatcher, getContext(java.lang.String), ServletConfig.getServletName()