javax.servlet.Servlet Maven / Gradle / Ivy
/*
* JBoss, Home of Professional Open Source.
* Copyright 2007, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package javax.servlet;
import java.io.IOException;
/**
* Defines methods that all servlets must implement.
*
* A servlet is a small Java program that runs within a Web server. Servlets
* receive and respond to requests from Web clients, usually across HTTP, the
* HyperText Transfer Protocol.
*
* To implement this interface, you can write a generic servlet that extends
* javax.servlet.GenericServlet or an HTTP servlet that extends
* javax.servlet.http.HttpServlet.
*
* This interface defines methods to initialize a servlet, to service requests,
* and to remove a servlet from the server. These are known as life-cycle
* methods and are called in the following sequence:
*
* - The servlet is constructed, then initialized with the
init
* method.
* - Any calls from clients to the
service method are handled.
* - The servlet is taken out of service, then destroyed with the
*
destroy method, then garbage collected and finalized.
*
*
* In addition to the life-cycle methods, this interface provides the
* getServletConfig method, which the servlet can use to get any
* startup information, and the getServletInfo method, which
* allows the servlet to return basic information about itself, such as author,
* version, and copyright.
*
* @author Various
* @see GenericServlet
* @see javax.servlet.http.HttpServlet
*/
public interface Servlet
{
/**
* Called by the servlet container to indicate to a servlet that the servlet
* is being placed into service.
*
* The servlet container calls the init method exactly once
* after instantiating the servlet. The init method must
* complete successfully before the servlet can receive any requests.
*
* The servlet container cannot place the servlet into service if the
* init method
*
* - Throws a
ServletException
* - Does not return within a time period defined by the Web server
*
*
* @param config
* a ServletConfig object containing the servlet's
* configuration and initialization parameters
* @exception ServletException
* if an exception has occurred that interferes with the
* servlet's normal operation
* @see UnavailableException
* @see #getServletConfig
*/
public void init(ServletConfig config) throws ServletException;
/**
* Returns a {@link ServletConfig} object, which contains initialization and
* startup parameters for this servlet. The ServletConfig
* object returned is the one passed to the init method.
*
* Implementations of this interface are responsible for storing the
* ServletConfig object so that this method can return it. The
* {@link GenericServlet} class, which implements this interface, already
* does this.
*
* @return the ServletConfig object that initializes this
* servlet
* @see #init
*/
public ServletConfig getServletConfig();
/**
* Called by the servlet container to allow the servlet to respond to a
* request.
*
* This method is only called after the servlet's init()
* method has completed successfully.
*
* The status code of the response always should be set for a servlet that
* throws or sends an error.
*
* Servlets typically run inside multithreaded servlet containers that can
* handle multiple requests concurrently. Developers must be aware to
* synchronize access to any shared resources such as files, network
* connections, and as well as the servlet's class and instance variables.
* More information on multithreaded programming in Java is available in
* the Java tutorial on multi-threaded programming.
*
* @param req
* the ServletRequest object that contains the
* client's request
* @param res
* the ServletResponse object that contains the
* servlet's response
* @exception ServletException
* if an exception occurs that interferes with the servlet's
* normal operation
* @exception IOException
* if an input or output exception occurs
*/
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;
/**
* Returns information about the servlet, such as author, version, and
* copyright.
*
* The string that this method returns should be plain text and not markup of
* any kind (such as HTML, XML, etc.).
*
* @return a String containing servlet information
*/
public String getServletInfo();
/**
* Called by the servlet container to indicate to a servlet that the servlet
* is being taken out of service. This method is only called once all threads
* within the servlet's service method have exited or after a
* timeout period has passed. After the servlet container calls this method,
* it will not call the service method again on this servlet.
*
* This method gives the servlet an opportunity to clean up any resources
* that are being held (for example, memory, file handles, threads) and make
* sure that any persistent state is synchronized with the servlet's current
* state in memory.
*/
public void destroy();
}