1. What is a Declaration?
 
Answer: A declaration declares one or more variables or methods for use later in the JSP source file.
A declaration must contain at least one complete declarative statement. You can declare any number of variables or methods within one declaration tag, as long as they are separated by semicolons. The declaration must be valid in the scripting language used in the JSP file.

<%! somedeclarations %>
<%! int i = 0; %>
<%! int a, b, c; %>
 

2. What are the different scope valiues for the <jsp:useBean>?
 
Answer: The different scope values for <jsp:useBean> are

1. page
2. request
3.session
4.application

3. How do I prevent the output of my JSP or Servlet pages from being cached by the browser?
 
Answer: 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
%>

4. 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");
%>
<a href=\'<%=url%>\'>hello2.jsp</a>

hello2.jsp
<%@ page session="true" %>
<%
Integer i= (Integer )session.getValue("num");
out.println("Num value in session is " + i.intValue());
%>

5. What is a output comment
Answer: A comment that is sent to the client in the viewable page source. The JSP engine handles an output comment as un-interpreted HTML text, returning the comment in the HTML output sent to the client. You can see the comment by viewing the page source from your Web browser.

6. What are the implicit objects
Answer: List them. 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 are:

   1. request
   2. response
   3. pageContext
   4. session
   5. application
   6. out
   7. config
   8. page
   9. exception

7. How do I use comments within a JSP page
Answer: 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 -->

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
    **/
    %>

8. How can I declare methods within my JSP page
Answer: You can declare methods for use within your JSP page as declarations. The methods can then be invoked within any other methods you declare, or within JSP scriptlets and expressions. Do note that you do not have direct access to any of the JSP implicit objects like request, response, session and so forth from within JSP methods. However, you should be able to pass any of the implicit JSP variables as parameters to the methods you declare. For example:
    <%!
    public String whereFrom(HttpServletRequest req) {
    HttpSession ses = req.getSession();
    ...
    return req.getRemoteHost();
    }
    %>
    <%
    out.print("Hi there, I see that you are coming in from ");
    %>
    <%= whereFrom(request) %>
    Another Example
    file1.jsp:
    <%@page contentType="text/html"%>
    <%!
    public void test(JspWriter writer) throws IOException{
    writer.println("Hello!");
    }
    %>
    file2.jsp
    <%@include file="file1.jsp"%>
  
  
    <%test(out);% >
  
  

9. How do I include static files within a JSP page?

Static resources should always be included using the JSP include directive. This way, the inclusion is performed just once during the translation phase. Do note that you should always supply a relative URL for the file attribute. Although you can also include static resources using the action, this is not advisable as the inclusion is then performed for each and every request.

10. Why are JSP pages the preferred API for creating a web-based client program?

Because no plug-ins or security policy files are needed on the client systems(applet does). Also, JSP pages enable cleaner and more module application design because they provide a way to separate applications programming from web page design. This means personnel involved in web page design do not need to understand Java programming language syntax to do their jobs.