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Servlet API

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The Servlet API is supported by all Servlet containers, such as Tomcat and Weblogic, etc. The Application Programming Interface (API) contains interface and classes to write a servlet program. The servlet API contains two packages as listed below:

  • javax.servlet
  • javax.servlet.http

Package javax.servlet

javax.servlet contains a number of classes and interface that allows the servlet to access the basic services provided by the servlet container. Following table lists the classes and interface of javax.servlet package:

Name Description Type
Servlet Defines methods that a servlet class must implement Interface
ServletConfig During initialization it allows the servlet container to pass information to a servlet. Interface
ServletContext Servlet Context is used to communicate with the servlet container to get the details of web application. Interface
ServletContextListener Receive notification about the changes made to the servlet context of the Web application. Interface
ServletRequest It is used to request client information to the servlet Interface
ServletResponse It is used by servlet to write the response content to the client. Interface
SingleThreadModel It uses the servlet instance to process only one request at a time. Interface
ServletRequestListener In the web component it receives a notification of the particular request that is coming in or out Interface
ServletRequestAttributeListener Notifies the changes in request attribute Interface
ServletContextAttributeListener The servlet context receives notification of the changes to be made on attribute list. Interface
Filter It is a reusable code that can transform the content of request, responses and the header information from one format to another. Interface
FilterChain Stores information about a chain of filters. Interface
FilterConfig It is used during the initialization. Interface
RequestDispatcher It is used to dispatch the request from one component to another. Interface
ServletContextEvent It gives the details of the life cycle events of the ServletContext object. Class
ServletRequestEvent Indicates that the request that is about to come in or go out of the web component. Class
ServletRequestWrapper Provides implementation of the ServletRequest interface to receive the request from a servlet. Class
ServletResponseWrapper Provides implementation of the ServletResponse interface to send response to the servlet. Class
ServletRequestAttributeEvent Servlet container invokes this method to indicate whether the attribute is to be added into the request, removed or replaced from the request. Class
ServletContextAttributeEvent Servlet container invokes this method to indicate whether the attribute is to be added into the context, removed or replaced from the context. Class
ServletInputStream Provides an input stream for reading a client requests. Class
ServletOutputStream Provides an output stream for writing servlet response to client. Class
GenericServlet Implements javax.servlet.Servlet interface and provides the basic implementation for the methods in this interface. Class
ServletException It is used to indicate that the request has generate an error. Class
UnavailableException Indicates that the servlet is currently unavailable to the process. Class

Package javax.servlet.http

The servlets using HTTP protocol are supported by the package javax.servlet.http. The list of classes and interface of javax.servlet.http package are listed in the following table:

Name Description Type
HttpServletRequest The web container provides implementation to this interface and encapsulates all HTTP based request information. Interface
HttpServletResponse Provide HTTP- specific functionality while sending a response. Interface
HttpSession It is a mechanism for storing client data across multiple HTTP requests. Interface
HttpSessionBindingListener Notifies when the objects of its implementation class is added or removed from the session. Interface
Cookie It is a file containing the information that is sent by web server to a client. Class
HttpSessionBindingEvent This method is used to indicate whether the object is added into the HttpSession object or removed from the HttpSession object. Class
HttpServlet Provides convenient methods for implementing for handling HTTP request. Class

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About Krishna Srinivasan

He is Founder and Chief Editor of JavaBeat. He has more than 8+ years of experience on developing Web applications. He writes about Spring, DOJO, JSF, Hibernate and many other emerging technologies in this blog.