javax.servlet.http

Class HttpServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

All Implemented Interfaces:

java.io.Serializable, Servlet, ServletConfig

Direct Known Subclasses:

AdminRestServlet, DirectoryServlet, HessianServlet, HmtpServlet, JMSServlet, ProfilerServlet, QuercusServlet, QuercusServletImpl, SSIServlet

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

HttpServlet is a convenient abstract class for creating servlets. Normally, servlet writers will only need to override doGet or doPost.

Caching

HttpServlet makes caching simple. Just override getLastModified. As long as the page hasn't changed, it can avoid the overhead of any heavy processing or database queries. You cannot use getLastModified if the response depends on sessions, cookies, or any headers in the servlet request.

Hello, world

The Hello.java belongs in myapp/WEB-INF/classes/test/Hello.java under the application's root. Normally, it will be called as http://myhost.com/myapp/servlet/test.Hello. If the server doesn't use applications, then use /servlet/test.Hello.

 package test;

 import java.io.*;
 import javax.servlet.*;
 import javax.servlet.http.*;

 public class Hello extends HttpServlet {
   public void doGet(HttpServletRequest request,
                          HttpServletResponse response)
     throws ServletException, IOException
   {
     response.setContentType("text/html");
     PrintWriter out = response.getWriter();
     out.println("Hello, World");
     out.close();
   }
 }
 

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
HttpServlet()

Method Summary

Modifier and Type	Method and Description
protected void	doDelete(HttpServletRequest req, HttpServletResponse res) Process a DELETE request
protected void	doGet(HttpServletRequest req, HttpServletResponse res) Process a GET or HEAD request
protected void	doHead(HttpServletRequest req, HttpServletResponse res) Process a HEAD request.
protected void	doOptions(HttpServletRequest req, HttpServletResponse res) Process an OPTIONS request
protected void	doPost(HttpServletRequest req, HttpServletResponse res) Process a POST request
protected void	doPut(HttpServletRequest req, HttpServletResponse res) Process a PUT request
protected void	doTrace(HttpServletRequest req, HttpServletResponse res) Process a TRACE request
protected long	getLastModified(HttpServletRequest req) Returns the last-modified time for the page for caching.
protected void	service(HttpServletRequest req, HttpServletResponse res) Services a HTTP request.
void	service(ServletRequest request, ServletResponse response) Service a request.

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Constructor Detail

HttpServlet

public HttpServlet()

Method Detail

service

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

Service a request. Normally not overridden. If you need to override this, use GenericServlet instead.

Specified by:

service in interface Servlet

Parameters:

request - request information. Normally servlets will cast this to HttpServletRequest

response - response information. Normally servlets will cast this to HttpServletRequest

Throws:

ServletException

java.io.IOException

service

protected void service(HttpServletRequest req,
                       HttpServletResponse res)
                throws ServletException,
                       java.io.IOException

Services a HTTP request. Automatically dispatches based on the request method and handles "If-Modified-Since" headers. Normally not overridden.

Parameters:

req - request information

res - response object for returning data to the client.

Throws:

ServletException

java.io.IOException

getLastModified

protected long getLastModified(HttpServletRequest req)

Returns the last-modified time for the page for caching. If at all possible, pages should override getLastModified to improve performance. Servlet engines like Resin can cache the results of the page, resulting in near-static performance.

Parameters:

req - the request

Returns:

the last-modified time of the page.

doHead

protected void doHead(HttpServletRequest req,
                      HttpServletResponse res)
               throws ServletException,
                      java.io.IOException

Process a HEAD request. By default, uses doGet.

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doGet

protected void doGet(HttpServletRequest req,
                     HttpServletResponse res)
              throws ServletException,
                     java.io.IOException

Process a GET or HEAD request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doPost

protected void doPost(HttpServletRequest req,
                      HttpServletResponse res)
               throws ServletException,
                      java.io.IOException

Process a POST request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doPut

protected void doPut(HttpServletRequest req,
                     HttpServletResponse res)
              throws ServletException,
                     java.io.IOException

Process a PUT request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doDelete

protected void doDelete(HttpServletRequest req,
                        HttpServletResponse res)
                 throws ServletException,
                        java.io.IOException

Process a DELETE request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doOptions

protected void doOptions(HttpServletRequest req,
                         HttpServletResponse res)
                  throws ServletException,
                         java.io.IOException

Process an OPTIONS request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException

doTrace

protected void doTrace(HttpServletRequest req,
                       HttpServletResponse res)
                throws ServletException,
                       java.io.IOException

Process a TRACE request

Parameters:

req - the client request

res - response to the client

Throws:

ServletException

java.io.IOException