Java Servlet API allows a software developer to add dynamic content to a Web server using the Java platform. The generated content is commonly HTML, but may be other data such as XML. Servlets are the Java counterpart to dynamic web content technologies such as CGI, PHP or ASP. Servlets can maintain state across many server transactions by using HTTP cookies, session variables or URL rewriting.
The Servlet API, contained in the Java package hierarchy javax.servlet, defines the expected interactions of a web container and a servlet. A web container is essentially the component of a web server that interacts with the servlets. The web container is responsible for managing the lifecycle of servlets, mapping a URL to a particular servlet and ensuring that the URL requester has the correct access rights.
A Servlet is an object that receives requests (ServletRequest) and generates a response (ServletResponse) based on the request. The API package javax.servlet.http defines HTTP subclasses of the generic servlet (HttpServlet) request (HttpServletRequest) and response (HttpServletResponse) as well as an (HttpSession) that tracks multiple requests and responses between the web server and a client. Servlets may be packaged in a WAR file as a Web application.
Moreover, servlets can be generated automatically by JavaServer Pages (JSP), or alternately by template engines such as WebMacro. Often servlets are used in conjunction with JSPs in a pattern called “Model 2”, which is a flavor of the model-view-controller pattern.
History
The original servlet specification was created by Sun Microsystems (version 1.0 was finalized in June 1997). Starting with version 2.3, the servlet specification was developed under the Java Community Process. JSR 53 defined both the Servlet 2.3 and JavaServer Page 1.2 specifications. JSR 154 specifies the Servlet 2.4 and 2.5 specifications. As of May 10, 2006, the current version of the servlet specification is 2.5. Read the rest of this entry »
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