Ans) JSP (Java ServerPages) is an extension of the Java Servlet technology. JSP is commonly used as the presentation layer for combining HTML and Java code. While Java Servlet technology is capable of generating HTML with out.println(“….. �) statements, where out is a PrintWriter. This process of embedding HTML code with escape characters is cumbersome and hard to maintain. The JSP technology solves this by providing a level of abstraction so that the developer can use custom tags and action elements, which can speed up Web development and are easier to maintain.

The JSPs have a translation or a compilation process where the JSP engine translates and compiles a JSP file into a JSP Servlet. The translated and compiled JSP Servlet moves to the execution phase (run time) where they can handle requests and send response.

Unless explicitly compiled ahead of time, JSP files are compiled the first time they are accessed. On large production sites, or in situations involving complicated JSP files, compilation may cause unacceptable delays to users first accessing the JSP page. The JSPs can be compiled ahead of time (ie precompiled) using application server tools/settings or by writing your own script.

Ans) Pre-translated: Before the JSP file has been translated and compiled into the Servlet.
Translated: The JSP file has been translated and compiled as a Servlet.
Initialized: Prior to handling the requests in the service method the container calls the jspInit() to initialize the Servlet. Called only once per Servlet instance.
Servicing: Services the client requests. Container calls this method for each request.
Out of service: The Servlet instance is out of service. The container calls the jspDestroy() method.

Ans)
Declaration Element: is the embedded Java declaration statement, which gets inserted at the Servlet class level.
<%! Calendar c = Calendar.getInstance(); %>
Important: declaring variables via this element is not thread-safe, because this variable ends up in the generated Servlet as an instance variable, not within the body of the _jspservice() method. Ensure their access is either read-only or synchronized.

Expression Element: is the embedded Java expression, which gets evaluated by the service method.
<%= new Date()>

Scriptlet Elements: are the embedded Java statements, which get executed as part of the service method.
(Note: Not recommended to use Scriptlet elements because they don’t provide reusability and maintainability. Use custom tags (like JSTL, JSF tags, etc) or beans instead).
<%
//Java codes
String userName=null;
userName=request.getParameter("userName");
%>

Action Elements: A JSP element that provides information for execution phase.
<jsp:useBean id="object_name" class="class_name"/>
<jsp:include page="scripts/login.jsp" />

Directive Elements: A JSP element that provides global information for the translation phase.
<%@ page import=�java.util.Date� %>
<%@ include file=�myJSP� %>
<%@ taglib uri=�tagliburi� prefix=�myTag�%>

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Ans) No. The declaration of variables in JSP is not thread-safe, because the declared variables end up in the generated Servlet as an instance variable, not within the body of the _jspservice() method.
The following declaration is not thread safe: because these are declarations, and will only be evaluated once when the page is loaded
<%! int a = 5 %>
The following declaration is thread safe: because the variables declared inside the scriplets have the local scope and not shared.
<% int a = 5 %>;