HttpServlet class

The HttpServlet class extends the GenericServlet class and implements Serializable interface. It provides http specific methods such as doGet, doPost, doHead, doTrace etc.

we should extend our servlet class with HttpServlet abstract class in order to get protocol dependent (http) services. When ever we make request to the servlet the following methods will be called automatically by the container.

  1. Container first calls public Service() method
  2. Public Service() method internally calls protected service method
  3. Protected Service() method will internally calling doGet() or doPost() (i mean doXxx() methods, its depends on the type of http method used by the client )
  4. If the client is not specifying the type of Http method then Http protocol by default consider GET method, so finally the client request is processed at doGet() method

There are many methods in HttpServlet class:

  1. public void service(ServletRequest req,ServletResponse res) dispatches the request to the protected service method by converting the request and response object into http type.
  2. protected void service(HttpServletRequest req, HttpServletResponse res) receives the request from the service method, and dispatches the request to the doXXX() method depending on the incoming http request type.
  3. protected void doGet(HttpServletRequest req, HttpServletResponse res) handles the GET request. It is invoked by the web container.
  4. protected void doPost(HttpServletRequest req, HttpServletResponse res) handles the POST request. It is invoked by the web container.
  5. protected void doHead(HttpServletRequest req, HttpServletResponse res) handles the HEAD request. It is invoked by the web container.
  6. protected void doOptions(HttpServletRequest req, HttpServletResponse res) handles the OPTIONS request. It is invoked by the web container.
  7. protected void doPut(HttpServletRequest req, HttpServletResponse res) handles the PUT request. It is invoked by the web container.
  8. protected void doTrace(HttpServletRequest req, HttpServletResponse res) handles the TRACE request. It is invoked by the web container.
  9. protected void doDelete(HttpServletRequest req, HttpServletResponse res) handles the DELETE request. It is invoked by the web container.
  10. protected long getLastModified(HttpServletRequest req) returns the time when HttpServletRequest was last modified since midnight August 15, 1992 GMT