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Chapter 7 using JSP

• JSP directive : <%@ page import="java.util.*" %>
• Scriptlet : <% %> ==> goes into _jspService()
• Expression: <%= %> ==> No semicolons at the end of statement
• Declaration: <%! int count=0; %> ==> Class declaration . Variables & other methods definition . You can override jspInit() here.
• Comment: <%-- --%>

* Implicit objects can be used with in Scriptlet are:
out, request,response,session(if session is enabled) , application, config, exception(only in errorpage) , pageContext (has reference to other implicit objects), page

These implicit objects are in fact java variable names pre defined in _jspService().

*JSP converted servlet life cycle: jspInit() ==> _jspService() ==> jspDestroy()
You can override jspInit and jspDestroy, but can’t override _jspService

*If you want to define Servlet initialization for a JSP,

<servlet>
	</servlet><servlet -name>test1</servlet>
	<jsp -file>/Test.jsp</jsp> <!--we use jsp-file instead of servlet-class-->
	<init -param>
		<param -name>email</param>
		<param -value>email@email.com</param>
	</init>
 
<servlet -mapping>
	</servlet><servlet -name>test1</servlet>
	<url -parttern>/Test.jsp</url> <!-- If you define servlet for JSP, you must define servlet mapping for this page.-->

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Chapter 6 Session Management

Session

HttpSession ss = request.getSession();
ss.isNew(); // < == return True if just created.

• JSESSIONID cookie name is used for session management. Its automatically done by Container.
• request.getSession(false); // Do not create new session. Only get preexisting session.
• request.getSession(true); // Create new session. Same as the getSession()
• HttpSessionEvent or HttpSessionBindingEvent have getSession() function.
• If cookie is disabled, isNew will always return TRUE
• URL writing : if client does not support cookie, container automatically use URL rewriting for session support. It adds ";jsessionid=1234567" at the end of the URL. However you need to use response.encodeURL("/test.do") to print the URL or response.encodeRedirectURL("/test.do") for redirect

Session Methods

• getCreationTime()
• getLastAccessedTime()
• setMaxInactiveInterval() : max time to keep the session in Seconds. Negative value ==> session never timeout
• getMaxInactiveInterval()
• invalidate() : Ends the session. Session ID no longer exists and attributes are removed.

DD : Define Max Session time in minutes.

<session -config>
	</session><session -timeout>15</session>

For DD session-timeout value, 0 or negative means ==> Session never expires (little bit different from setMaxInactiveInterval )

Cookie

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Chapter 5 Attribute and listeners

Servlet Init Parameter : available only for that servlet. Defined within the specific servlet.
DD

<servlet>
	</servlet><servlet -name>Servlet Name</servlet>
	<servlet -class>com.test.ServletClass</servlet>
	<init -param>
		<param -name>Email</param>
		<param -value>admin@email.com</param>
	</init>

In servlet

ServletConfig sc = getServletConfig();
String email = sc.getInitParameter("EMAIL");

• You can use getInitParameterNames() to go through all init parameters
• Also note ServletConfig will not be available in forwarding JSP. The ServletConfig init parameters must be passed to JSP as other scope’s Attributes.

Context Init Parameter: available for all the servlets in the application
Note that the <context-param> element does not reside within <servlet> element

<servlet> ... </servlet>
<context -param>
	<param -name>AlertEmail</param>
	<param -value>alertall@email.com</param>
</context>

In servlet

ServletContext scx = getServletContext();
String email = scx.getInitParameter("AlertEmail");

• Context Param can be accessed from any Servlet and JSP within the application

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