Java Guru: Identify the advantages of JSP over Servlet.

Answer:
a) Embedding of Java code in HTML pages
b) Platform independence
c) Creation of database-driven Web applications
d) Server-side programming capabilities

Question: What do you understand by JSP Actions?
Answer: JSP actions are XML tags that direct the server to use existing components or control the behavior of the JSP engine. JSP Actions consist of a typical (XML-based) prefix of "jsp" followed by a colon, followed by the action name followed by one or more attribute parameters.

There are six JSP Actions:

<jsp:include/>

<jsp:forward/>

<jsp:plugin/>

<jsp:usebean/>

<jsp:setProperty/>

<jsp:getProperty/>

Question: What is the difference between <jsp:include page = ... > and
<%@ include file = ... >?.
Answer: Both the tag includes the information from one page in another. The differences are as follows:<jsp:include page = ... >: This is like a function call from one jsp to another jsp. It is executed ( the included page is executed and the generated html content is included in the content of calling jsp) each time the client page is accessed by the client. This approach is useful to for modularizing the web application. If the included file changed then the new content will be included in the output.

<%@ include file = ... >: In this case the content of the included file is textually embedded in the page that have <%@ include file=".."> directive. In this case in the included file changes, the changed content will not included in the output. This approach is used when the code from one jsp file required to include in multiple jsp files.

Question: What is the difference between <jsp:forward page = ... > and
response.sendRedirect(url),?.
Answer: The <jsp:forward> element forwards the request object containing the client request information from one JSP file to another file. The target file can be an HTML file, another JSP file, or a servlet, as long as it is in the same application context as the forwarding JSP file.
sendRedirect sends HTTP temporary redirect response to the browser, and browser creates a new request to go the redirected page. The response.sendRedirect kills the session variables.

Answer :- Embedding of Java code in HTML pages

Write the following code for a JSP page:
<%@ page language = "java" %>

<HTML>
<HEAD><TITLE>RESULT PAGE</TITLE></HEAD>
<BODY>
<%

PrintWriter print = request.getWriter();
print.println("Welcome");

%>
</BODY>
</HTML>
Suppose you access this JSP file, Find out your answer.
a) A blank page will be displayed.
b) A page with the text Welcome is displayed
c) An exception will be thrown because the implicit out object is not used
d) An exception will be thrown because PrintWriter can be used in servlets only

Answer :- A page with the text Welcome is displayed

Question: What are implicit Objects available to the JSP Page?
Answer: Implicit objects are the objects available to the JSP page. These objects are created by Web container and contain information related to a particular request, page, or application. The JSP implicit objects are:

Variable	Class	Description
application	javax.servlet.ServletContext	The context for the JSP page's servlet and any Web components contained in the same application.
config	javax.servlet.ServletConfig	Initialization information for the JSP page's servlet.
exception	java.lang.Throwable	Accessible only from an error page.
out	javax.servlet.jsp.JspWriter	The output stream.
page	java.lang.Object	The instance of the JSP page's servlet processing the current request. Not typically used by JSP page authors.
pageContext	javax.servlet.jsp.PageContext	The context for the JSP page. Provides a single API to manage the various scoped attributes.
request	Subtype of javax.servlet.ServletRequest	The request triggering the execution of the JSP page.
response	Subtype of javax.servlet.ServletResponse	The response to be returned to the client. Not typically used by JSP page authors.
session	javax.servlet.http.HttpSession	The session object for the client.

Question: What are all the different scope values for the <jsp:useBean> tag?
Answer:<jsp:useBean> tag is used to use any java object in the jsp page. Here are the scope values for <jsp:useBean> tag:
a) page
b) request
c) session and
d) application

Question: What is JSP Output Comments?
Answer: JSP Output Comments are the comments that can be viewed in the HTML source file.
Example: 
and

Question: What is expression in JSP?
Answer: Expression tag is used to insert Java values directly into the output. Syntax for the Expression tag is: <%= expression %>
An expression tag contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file. The following expression tag displays time on the output:<%=new java.util.Date()%>

Question: What types of comments are available in the JSP?
Answer: There are two types of comments are allowed in the JSP. These are hidden and output comments. A hidden comments does not appear in the generated output in the html, while output comments appear in the generated output.
Example of hidden comment:<%-- This is hidden comment --%>
Example of output comment:

Question: What is JSP declaration?
Answer: JSP Decleratives are the JSP tag used to declare variables. Declaratives are enclosed in the <%! %> tag and ends in semi-colon. You declare variables and functions in the declaration tag and can use anywhere in the JSP. Here is the example of declaratives:

<%@page contentType="text/html" %>

<html>

<body>

<%!
int cnt=0;
private int getCount(){
//increment cnt and return the value
cnt++;
return cnt;
}
%>

<p>Values of Cnt are:</p>

</body>

</html>

Question: What is JSP Scriptlet?
Answer: JSP Scriptlet is jsp tag which is used to enclose java code in the JSP pages. Scriptlets begins with <% tag and ends with %> tag. Java code written inside scriptlet executes every time the JSP is invoked.
Example: <%
//java codes
   String userName=null;
   userName=request.getParameter("userName");
   %>

Question: What are the life-cycle methods of JSP?
Answer: Life-cycle methods of the JSP are:
a) jspInit(): The container calls the jspInit() to initialize the servlet instance. It is called before any other method, and is called only once for a servlet instance.
b)_jspService(): The container calls the _jspservice() for each request and it passes the request and the response objects. _jspService() method cann't be overridden.
c) jspDestroy(): The container calls this when its instance is about to destroyed.
The jspInit() and jspDestroy() methods can be overridden within a JSP page

Question: What do you understand by JSP translation?
Answer: JSP translators generate standard Java code for a JSP page implementation class. This class is essentially a servlet class wrapped with features for JSP functionality.

Question: What you can stop the browser to cash your page?
Answer: Instead of deleting a cache, you can force the browser not to catch the page.
<%
response.setHeader("pragma","no-cache");//HTTP 1.1
response.setHeader("Cache-Control","no-cache");
response.setHeader("Cache-Control","no-store");
response.addDateHeader("Expires", -1);
response.setDateHeader("max-age", 0);
//response.setIntHeader ("Expires", -1); //prevents caching at the proxy server
response.addHeader("cache-Control", "private");

%>
put the above code in your page.

Question: What you will handle the runtime exception in your jsp page?
Answer: The errorPage attribute of the page directive can be used to catch run-time exceptions automatically and then forwarded to an error processing page.

For example:
<%@ page errorPage="customerror.jsp" %>
above code forwards the request to "customerror.jsp" page if an uncaught exception is encountered during request processing. Within "customerror.jsp", you must indicate that it is an error-processing page, via the directive: <%@ page isErrorPage="true" %>.

Identify the advantages of JSP over Servlet.

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