1. What is a Expression?
 
Answer: 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. Because the value of an expression is converted to a String, you can use an expression within text in a JSP file. Like
<%= someexpression %>
<%= (new java.util.Date()).toLocaleString() %>
You cannot use a semicolon to end an expression 
   
2. What are implicit objects? List them?
 
Answer: Certain objects that are available for the use in JSP documents without being declared first. These objects are parsed by the JSP engine and inserted into the generated servlet. The implicit objects re listed below
request
response
pageContext
session
application
out
config
page
exception
 
3. What are context initialization parameters
Answer: Context initialization parameters are specified by the in the web.xml file, these are initialization parameter for the whole application and not specific to any servlet or JSP.

4. What is a Hidden Comment
Answer: A comment that documents the JSP page but is not sent to the client. The JSP engine ignores a hidden comment, and does not process any code within hidden comment tags. A hidden comment is not sent to the client, either in the displayed JSP page or the HTML page source. The hidden comment is useful when you want to hide or “comment out” part of your JSP page.

5. 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.
The following example shows the "today" property of the Foo bean initialized to the current date when it is instantiated. Note that here, we make use of a JSP expression within the jsp:setProperty action.

value="<%=java.text.DateFormat.getDateInstance().format(new java.util.Date()) %>"/ >
<%-- scriptlets calling bean setter methods go here --%>"

6. How can I enable session tracking for JSP pages if the browser has disabled cookies
Answer: We know that session tracking uses cookies by default to associate a session identifier with a unique user. If the browser does not support cookies, or if cookies are disabled, you can still enable session tracking using URL rewriting. URL rewriting essentially includes the session ID within the link itself as a name/value pair. However, for this to be effective, you need to append the session ID for each and every link that is part of your servlet response. Adding the session ID to a link is greatly simplified by means of of a couple of methods: response.encodeURL() associates a session ID with a given URL, and if you are using redirection, response.encodeRedirectURL() can be used by giving the redirected URL as input. Both encodeURL() and encodeRedirectedURL() first determine whether cookies are supported by the browser; if so, the input URL is returned unchanged since the session ID will be persisted as a cookie. Consider the following example, in which two JSP files, say hello1.jsp and hello2.jsp, interact with each other. Basically, we create a new session within hello1.jsp and place an object within this session. The user can then traverse to hello2.jsp by clicking on the link present within the page.Within hello2.jsp, we simply extract the object that was earlier placed in the session and display its contents. Notice that we invoke the encodeURL() within hello1.jsp on the link used to invoke hello2.jsp; if cookies are disabled, the session ID is automatically appended to the URL, allowing hello2.jsp to still retrieve the session object. Try this example first with cookies enabled. Then disable cookie support, restart the brower, and try again. Each time you should see the maintenance of the session across pages. Do note that to get this example to work with cookies disabled at the browser, your JSP engine has to support URL rewriting.
    hello1.jsp
    <%@ page session="true" %>
    <%
    Integer num = new Integer(100);
    session.putValue("num",num);
    String url =response.encodeURL("hello2.jsp");
    %>
    hello2.jsp
    <%@ page session="true" %>
    <%
    Integer i= (Integer )session.getValue("num");
    out.println("Num value in session is "+i.intValue());

7. What are stored procedures? How is it useful?

A stored procedure is a set of statements/commands which reside in the database. The stored procedure is pre-compiled and saves the database the effort of parsing and compiling sql statements everytime a query is run. Each database has its own stored procedure language, usually a variant of C with a SQL preproceesor. Newer versions of db’s support writing stored procedures in Java and Perl too. Before the advent of 3-tier/n-tier architecture it was pretty common for stored procs to implement the business logic( A lot of systems still do it). The biggest advantage is of course speed. Also certain kind of data manipulations are not achieved in SQL. Stored procs provide a mechanism to do these manipulations. Stored procs are also useful when you want to do Batch updates/exports/houseKeeping kind of stuff on the db. The overhead of a JDBC Connection may be significant in these cases.

8. How many messaging models do JMS provide for and what are they?

JMS provide for two messaging models, publish-and-subscribe and point-to-point queuing.

9. Is JSP technology extensible?

YES. JSP technology is extensible through the development of custom actions, or tags, which are encapsulated in tag libraries.

10. What is the difference in using request.getRequestDispatcher() and context.getRequestDispatcher()
Answer: request.getRequestDispatcher(path): In order to create it we need to give the relative path of the resource,
context.getRequestDispatcher(path): In order to create it we need to give the absolute path of the resource.