September 18, 2008 at 6:07 PM
Difference between WebServer and Application Server
*) It serves pages for viewing in web browser.
*) It exclusively handles http requests.
*) It delegation model is fairly simple,when the request comes into the webserver,
*) It may not support transactions and database connection pooling.
*) It doesn't support EJB's.
*) Examples of Webserver are TOMAT ;
*) It Contains handlers for handling static content like html,images, scripts.
*)It provides exposes business logic for client applications through various protocols
*)It serves bussiness logic to application programs through any number of protocols.
*)It is more capable of dynamic behaviour than webserver.
*)It supports EJB's.
*)It provides load balancing , Transaction , more security .
*)Examples of AppServer are WEBLOGIC, WEBSPHERE.
*)It contains handlers for handling the requests to servlets, jsps i.e dynamic content,
it also contains container for EJBs.
*)It is very costly compared to the web-servers.
Implicit Objects in JSP are objects that are automatically available in JSP.
These objects are called implicit objects because they are automatically instantiated.
There are many implicit objects available. Some of them are:
request: The requested object is used to take the value from client?s web browser and pass it to the server.
response: The object response is of type Javax.servlet.http. >httpservletresponse.
The response object is also used with HTTP Headers.
Session: Session Objects is for maintaining states when there are multiple page requests.
Out: The Out object is written: Javax.servlet.jsp.JspWriter
PageContext: This is used to access page attributes and also to access all the namespaces associated with a JSP page.
The class or the interface name of the object PageContext is jsp.pageContext.
The object PageContext is written: Javax.servlet.jsp.pagecontext
Application: This is used to share the data with all application pages.
Config: This is used to get information regarding the Servlet configuration, stored in the Config object.
Page: The Page object denotes the JSP page, used for calling any instance of a Page's servlet.