JSP Interview Questions

 

How do I perform browser redirection from a JSP page?

You can use the response implicit object to redirect the browser to a different resource, as:
response.sendRedirect("http://www.sycorax.co.in/path/error.html");
You can also physically alter the Location HTTP header attribute, as shown below:

<%
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
String newLocn = "/newpath/index.html";
response.setHeader("Location",newLocn);
%>
You can also use the: <jsp:forward page="/newpage.jsp" />

Also note that you can only use this before any output has been sent to the client. I beleve this is the case with the response.sendRedirect() method as well. If you want to pass any paramateres then you can pass using <jsp:forward page="/servlet/login"><jsp:param name="username" value="sycorax" /> </jsp:forward>

How do you restrict page errors display in the JSP page?

You first set "Errorpage" attribute of PAGE directory to the name of the error page (ie Errorpage="error.jsp")in your jsp page .Then in the error jsp page set "isErrorpage=TRUE".
When an error occur in your jsp page it will automatically call the error page.

How do I use comments within a JSP page?

You can use "JSP-style" comments to selectively block out code while debugging or simply to comment your scriptlets. JSP comments are not visible at the client.
For example:
<%-- the scriptlet is now commented out
<%
out.println("Hello World");

%>
--%>;

You can also use HTML-style comments anywhere within your JSP page. These comments are visible at the client. For example:

<!-- (c) 2004 javagalaxy.com -->
Of course, you can also use comments supported by your JSP scripting language within your scriptlets.
For example, assuming Java is the scripting language, you can have:
<%
//some comment
/**
yet another comment
**/
%>

How do I prevent the output of my JSP or Servlet pages from being cached by the browser?

You will need to set the appropriate HTTP header attributes to prevent the dynamic content output by the JSP page from being cached by the browser. Just execute the following scriptlet at the beginning of your JSP pages to prevent them from being cached at the browser. You need both the statements to take care of some of the older browser versions.
<%
response.setHeader("Cache-Control","no-store"); //HTTP 1.1
response.setHeader("Pragma","no-cache"); //HTTP 1.0
response.setDateHeader ("Expires", 0); //prevents caching at the proxy server
%>

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