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.
- Container first calls public Service() method
- Public Service() method internally calls protected
service method
- 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 )
- 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:
- 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.
- 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.
- protected void doGet(HttpServletRequest req,
HttpServletResponse res) handles the GET request. It is invoked
by the web container.
- protected void doPost(HttpServletRequest req,
HttpServletResponse res) handles the POST request. It is
invoked by the web container.
- protected void doHead(HttpServletRequest req,
HttpServletResponse res) handles the HEAD request. It is
invoked by the web container.
- protected void doOptions(HttpServletRequest req,
HttpServletResponse res) handles the OPTIONS request. It is
invoked by the web container.
- protected void doPut(HttpServletRequest req,
HttpServletResponse res) handles the PUT request. It is invoked
by the web container.
- protected void doTrace(HttpServletRequest req,
HttpServletResponse res) handles the TRACE request. It is
invoked by the web container.
- protected void doDelete(HttpServletRequest req,
HttpServletResponse res) handles the DELETE request. It is
invoked by the web container.
- protected long getLastModified(HttpServletRequest
req) returns the time when HttpServletRequest was last modified
since midnight August 15, 1992 GMT