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Chapter 8 scriptless JSP

Accessing the JavaBean object using Standard Action (<jsp: >)

<jsp:useBean id="person" class="foo.Person" scope="request" />
<jsp:getProperty name="person" property="name" />

*jsp:useBean action tries to find the attribute name in the defined scope when there is any attribute match id name, it creates a new object using the class info defined in the class attribute.

*The useBean’s id attribute and the getProperty’s name should match.
getProperty’s property attribute is for getter and setter.

*setProperty is to set the member of the java Bean object.
<jsp:setProperty name="person" property="name" value="Fred" />

* if setProperty tag is used within useBean tag body, then it is used only conditionally when the bean object is created

<jsp:useBean id="person" class="foo.Person" scope="page" >
	<jsp:setProperty name="person" property="name" value="Fred" />
</jsp:useBean>

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

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

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

Cookie

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