javax.servlet.http

Class HttpServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

All Implemented Interfaces:

java.io.Serializable, Servlet, ServletConfig

public abstract class HttpServlet
extends GenericServlet
implements java.io.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.

Since:

1.0

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
HttpServlet() Does nothing

Method Summary

Methods

Modifier and Type	Method and Description
protected void	doDelete(HttpServletRequest request, HttpServletResponse response) This method is called on a "DELETE" request.
protected void	doGet(HttpServletRequest request, HttpServletResponse response) This method is called on a "GET" request.
protected void	doHead(HttpServletRequest request, HttpServletResponse response) This method is called on a "HEAD" request.
protected void	doOptions(HttpServletRequest request, HttpServletResponse response) This method is called on a "OPTIONS" request.
protected void	doPost(HttpServletRequest request, HttpServletResponse response) This method is called on a "POST" request.
protected void	doPut(HttpServletRequest request, HttpServletResponse response) This method is called on a "PUT" request.
protected void	doTrace(HttpServletRequest request, HttpServletResponse response) This method is called on a "TRACE" request.
protected long	getLastModified(HttpServletRequest request) Returns the time the requested uri was last modified in seconds since 1 january 1970.
protected void	service(HttpServletRequest request, HttpServletResponse response) 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.
void	service(ServletRequest request, ServletResponse response) Frontend for calling service(HttpServletRequest,HttpServletResponse).

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HttpServlet

public HttpServlet()

Does nothing

Method Detail

doGet

protected void doGet(HttpServletRequest request,
         HttpServletResponse response)
              throws ServletException,
                     java.io.IOException

This method is called on a "GET" request. The default implementation is that for HTTP/1.0 requests we return a HttpServletResponse.SC_BAD_REQUEST status code, and for HTTP/1.1 requests, HttpServletResponse.SC_METHOD_NOT_ALLOWED.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

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.

doHead

protected void doHead(HttpServletRequest request,
          HttpServletResponse response)
               throws ServletException,
                      java.io.IOException

This method is called on a "HEAD" request. This method calls the doGet method with the request parameter, but the response object is replaced by a HttpServletResponse that is identical to the reponse, but it has a "dummy" OutputStream.
The doGet method should perform a check like the following:
if(request.getMethod().equals("HEAD")) { ... }
if it wants to know whether it was called from doHead.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

Since:

2.0

doPost

protected void doPost(HttpServletRequest request,
          HttpServletResponse response)
               throws ServletException,
                      java.io.IOException

This method is called on a "POST" request. The default implementation is that for HTTP/1.0 requests we return a HttpServletResponse.SC_BAD_REQUEST status code, and for HTTP/1.1 requests, HttpServletResponse.SC_METHOD_NOT_ALLOWED.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

doPut

protected void doPut(HttpServletRequest request,
         HttpServletResponse response)
              throws ServletException,
                     java.io.IOException

This method is called on a "PUT" request. The default implementation is that for HTTP/1.0 requests we return a HttpServletResponse.SC_BAD_REQUEST status code, and for HTTP/1.1 requests, HttpServletResponse.SC_METHOD_NOT_ALLOWED.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

Since:

2.0

doDelete

protected void doDelete(HttpServletRequest request,
            HttpServletResponse response)
                 throws ServletException,
                        java.io.IOException

This method is called on a "DELETE" request. The default implementation is that for HTTP/1.0 requests we return a HttpServletResponse.SC_BAD_REQUEST status code, and for HTTP/1.1 requests, HttpServletResponse.SC_METHOD_NOT_ALLOWED.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

Since:

2.0

doOptions

protected void doOptions(HttpServletRequest request,
             HttpServletResponse response)
                  throws ServletException,
                         java.io.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 TRACE and OPTIONS are supported by default. GET, HEAD, POST, DELETE and PUT are added to this list if the subclass has its own implementation of the doGet, doHead, doPost, doDelete or doPut method respectively.

Throws:

ServletException - if an Servlet Exception occurs

java.io.IOException - if an IOException occurs

Since:

2.0

doTrace

protected void doTrace(HttpServletRequest request,
           HttpServletResponse response)
                throws ServletException,
                       java.io.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

java.io.IOException - if an IOException occurs

Since:

2.0

service

protected void service(HttpServletRequest request,
           HttpServletResponse response)
                throws ServletException,
                       java.io.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

java.io.IOException - an error has occured

service

public void service(ServletRequest request,
           ServletResponse response)
             throws ServletException,
                    java.io.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).

Specified by:

service in interface Servlet

Specified by:

service in class GenericServlet

Parameters:

request - The client's request

response - The class to write the response date to.

Throws:

ServletException - an error has occured

java.io.IOException - an error has occured

See Also:

SingleThreadModel