JSP Servlet J2EE Questions 17

81. What are JSP scripting elements?- JSP scripting elements lets to insert
Java code into the servlet that will be generated from the current JSP page. There
are three forms: a) Expressions of the form <%= expression %> that are evaluated
and inserted into the output, b) Scriptlets of the formthat are inserted into the
servlet’s service method, and c) Declarations of the form <%! Code %>that are
inserted into the body of the servlet class, outside of any existing methods.

82. What are JSP Directives?- A JSP directive affects the overall structure of
the servlet class. It usually has the following form:<%@ directive
attribute=”value” %> However, you can also combine multiple attribute settings for
a single directive, as follows:<%@ directive attribute1=”value1? attribute
2=”value2? . . . attributeN =”valueN” %> There are two main types of directive:
page, which lets to do things like import classes, customize the servlet
superclass, and the like; and include, which lets to insert a file into the servlet
class at the time the JSP file is translated into a servlet

83. What are Predefined variables or implicit objects?- To simplify code in JSP
expressions and scriptlets, we can use eight automatically defined variables,
sometimes called implicit objects. They are request, response, out, session,
application, config, pageContext, and page.

84. What are JSP ACTIONS?- JSP actions use constructs in XML syntax to control
the behavior of the servlet engine. You can dynamically insert a file, reuse
JavaBeans components, forward the user to another page, or generate HTML for the
Java plugin. Available actions include: jsp:include - Include a file at the time
the page is requested. jsp:useBean - Find or instantiate a JavaBean.
jsp:setProperty - Set the property of a JavaBean. jsp:getProperty - Insert the
property of a JavaBean into the output. jsp:forward - Forward the requester to a
newpage. Jsp: plugin - Generate browser-specific code that makes an OBJECT or EMBED

85. How do you pass data (including JavaBeans) to a JSP from a servlet?
(1)Request Lifetime: Using this technique to pass beans, a request dispatcher (using
either “include” or forward”) can be called. This bean will disappear after
processing this request has been completed. Servlet: request.
setAttribute(”theBean”, myBean); RequestDispatcher rd = getServletContext().
getRequestDispatcher(”thepage. jsp”); rd. forward(request, response); JSP
PAGE: < jsp: useBean id=”theBean” scope=”request” class=”. . . . . ” />(2) Session
Lifetime: Using this technique to pass beans that are relevant to a particular
session (such as in individual user login) over a number of requests. This bean
will disappear when the session is invalidated or it times out, or when you remove
it. Servlet: HttpSession session = request. getSession(true); session.
putValue(”theBean”, myBean); /* You can do a request dispatcher here, or just let
the bean be visible on the next request */ JSP Page:<jsp:useBean id=”theBean”
scope=”session” class=”. . . ” />3) Application Lifetime: Using this technique to
pass beans that are relevant to all servlets and JSP pages in a particular app, for
all users. For example, I use this to make a JDBC connection pool object available
to the various servlets and JSP pages in my apps. This bean will disappear when the
servlet engine is shut down, or when you remove it. Servlet: GetServletContext().
setAttribute(”theBean”, myBean); JSP PAGE:<jsp:useBean id=”theBean”

scope=”application” class=”. . . ” />