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**************************Java Servlettutorial*******************

Servlets are most often used to process or store a Java class inJava EE that conforms to the Java Servlet API,[2] a standard forimplementing Java classes that respond to requests. Servlets couldin principle communicate over any client–server protocol, but theyare most often used with the HTTP protocol. Thus "servlet" is oftenused as shorthand for "HTTP servlet".[3] Thus, a software developermay use a servlet to add dynamic content to a web server using theJava platform. The generated content is commonly HTML, but may beother data such as XML. Servlets can maintain state in sessionvariables across many server transactions by using HTTP cookies, orrewriting URLs.

To deploy and run a servlet, a web container must be used. A webcontainer (also known as a servlet container) is essentially thecomponent of a web server that interacts with the servlets. The webcontainer is responsible for managing the lifecycle of servlets,mapping a URL to a particular servlet and ensuring that the URLrequester has the correct access rights.

The Servlet API, contained in the Java package hierarchyjavax.servlet, defines the expected interactions of the webcontainer and a servlet.[3]

A Servlet is an object that receives a request and generates aresponse based on that request. The basic Servlet package definesJava objects to represent servlet requests and responses, as wellas objects to reflect the servlet's configuration parameters andexecution environment. The package javax.servlet.http definesHTTP-specific subclasses of the generic servlet elements, includingsession management objects that track multiple requests andresponses between the web server and a client. Servlets may bepackaged in a WAR file as a web application.

Servlets can be generated automatically from Java Server Pages(JSP) by the JavaServer Pages compiler. The difference betweenservlets and JSP is that servlets typically embed HTML inside Javacode, while JSPs embed Java code in HTML. While the direct usage ofservlets to generate HTML (as shown in the example below) hasbecome rare, the higher level MVC web framework in Java EE (JSF)still explicitly uses the servlet technology for the low levelrequest/response handling via the FacesServlet. A somewhat olderusage is to use servlets in conjunction with JSPs in a patterncalled "Model 2", which is a flavor of themodel–view–controller.

After learn this app Java Servlet tutorial will be help you knowservlet and implement a servlet with java.