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Class javax.servlet.http.HttpServlet

java.lang.Object
   |
   +----javax.servlet.GenericServlet
           |
           +----javax.servlet.http.HttpServlet

public abstract class HttpServlet
extends GenericServlet
implements Serializable
The mother-of-all-HttpServlets. Every normal http servlet extends this class and overrides either the doGet or doPost methods (or both). The server calls service. Service in its turn calls doGet, doPost, whatever, depending on the client's request.

Version:
Servlet API 2.0

Constructor Index

 o HttpServlet()
Does nothing

Method Index

 o doDelete(HttpServletRequest, HttpServletResponse)
This method is called on a "DELETE" request.
 o doGet(HttpServletRequest, HttpServletResponse)
This method is called on a "GET" request.
 o doOptions(HttpServletRequest, HttpServletResponse)
This method is called on a "OPTIONS" request.
 o doPost(HttpServletRequest, HttpServletResponse)
This method is called on a "POST" request.
 o doPut(HttpServletRequest, HttpServletResponse)
This method is called on a "PUT" request.
 o doTrace(HttpServletRequest, HttpServletResponse)
This method is called on a "TRACE" request.
 o getLastModified(HttpServletRequest)
Returns the time the requested uri was last modified in seconds since 1 january 1970.
 o service(HttpServletRequest, HttpServletResponse)
This method looks whether the request is a POST, GET, etc method, and then calls the appropriate doPost, doGet, whatever method.
If the request method is something it can't handle it sends a HttpServletResponse.SC_BAD_REQUEST error through the response.
 o service(ServletRequest, ServletResponse)
Frontend for calling service(HttpServletRequest,HttpServletResponse).

Constructors

 o HttpServlet
 public HttpServlet()
Does nothing

Methods

 o doDelete
 protected void doDelete(HttpServletRequest request,
                         HttpServletResponse response) throws ServletException, IOException
This method is called on a "DELETE" request. The default implementation is that HttpServletResponse.SC_BAD_REQUEST (error nr: 400) and the message "Method \"DELETE\" is not supported by this servlet" is returned to the client.

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o doGet
 protected void doGet(HttpServletRequest request,
                      HttpServletResponse response) throws ServletException, IOException
This method is called on a "GET" request. The default implementation is that HttpServletResponse.SC_BAD_REQUEST (error nr: 400) and the message "Method \"GET\" is not supported by this servlet" is returned to the client.

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o doOptions
 protected void doOptions(HttpServletRequest request,
                          HttpServletResponse response) throws ServletException, IOException
This method is called on a "OPTIONS" request. It tells the client which methods are supported by the servlet.
This comes down to an implementation where HEAD, TRACE and OPTIONS are supported by default because this class contains default implementations of them. GET, POST, DELETE and PUT are added to this list if the subclass has its own implementation of the doGet, doPost, doDelete or doPut method respectively. Note:
This implementation is probably not the most efficient one, but the whole OPTIONS thing is intended for debugging purposes, and this implementation does the job.

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o doPost
 protected void doPost(HttpServletRequest request,
                       HttpServletResponse response) throws ServletException, IOException
This method is called on a "POST" request. The default implementation is that HttpServletResponse.SC_BAD_REQUEST (error nr: 400) and the message "Method \"POST\" is not supported by this servlet" is returned to the client.

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o doPut
 protected void doPut(HttpServletRequest request,
                      HttpServletResponse response) throws ServletException, IOException
This method is called on a "PUT" request. The default implementation is that HttpServletResponse.SC_BAD_REQUEST (error nr: 400) and the message "Method \"PUT\" is not supported by this servlet" is returned to the client.

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o doTrace
 protected void doTrace(HttpServletRequest request,
                        HttpServletResponse response) throws ServletException, IOException
This method is called on a "TRACE" request. This method is for debugging purposes.
When a client makes a TRACE request the following is returned:
content type = "message/http"
message size: <size of the complete message>
first line of the message : TRACE <requested uri> <protocol>
on the following lines all the request header names and values

Throws: ServletException
if an Servlet Exception occurs
Throws: IOException
if an IOException occurs
 o getLastModified
 protected long getLastModified(HttpServletRequest request)
Returns the time the requested uri was last modified in seconds since 1 january 1970. Default implementation returns -1.

 o service
 protected void service(HttpServletRequest request,
                        HttpServletResponse response) throws ServletException, IOException
This method looks whether the request is a POST, GET, etc method, and then calls the appropriate doPost, doGet, whatever method.
If the request method is something it can't handle it sends a HttpServletResponse.SC_BAD_REQUEST error through the response.

Throws: ServletException
an error has occured
Throws: IOException
an error has occured
 o service
 public void service(ServletRequest request,
                     ServletResponse response) throws ServletException, IOException
Frontend for calling service(HttpServletRequest,HttpServletResponse).

This method tries to typecast the ServletRequest and the ServletResponse to HttpServletRequest and HttpServletResponse and then call service(HttpServletRequest,HttpServletResponse).

Parameters:
request - The client's request
response - The class to write the response date to.
Throws: ServletException
an error has occured
Throws: IOException
an error has occured
Overrides:
service in class GenericServlet

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