179 lines
6.7 KiB
Java
179 lines
6.7 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package javax.servlet;
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import java.io.IOException;
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/**
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* Defines methods that all servlets must implement.
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*
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* <p>
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* A servlet is a small Java program that runs within a Web server. Servlets
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* receive and respond to requests from Web clients, usually across HTTP, the
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* HyperText Transfer Protocol.
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*
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* <p>
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* To implement this interface, you can write a generic servlet that extends
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* <code>javax.servlet.GenericServlet</code> or an HTTP servlet that extends
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* <code>javax.servlet.http.HttpServlet</code>.
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*
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* <p>
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* This interface defines methods to initialize a servlet, to service requests,
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* and to remove a servlet from the server. These are known as life-cycle
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* methods and are called in the following sequence:
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* <ol>
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* <li>The servlet is constructed, then initialized with the <code>init</code>
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* method.
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* <li>Any calls from clients to the <code>service</code> method are handled.
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* <li>The servlet is taken out of service, then destroyed with the
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* <code>destroy</code> method, then garbage collected and finalized.
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* </ol>
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*
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* <p>
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* In addition to the life-cycle methods, this interface provides the
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* <code>getServletConfig</code> method, which the servlet can use to get any
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* startup information, and the <code>getServletInfo</code> method, which allows
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* the servlet to return basic information about itself, such as author,
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* version, and copyright.
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*
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* @see GenericServlet
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* @see javax.servlet.http.HttpServlet
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*/
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public interface Servlet {
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/**
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* Called by the servlet container to indicate to a servlet that the servlet
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* is being placed into service.
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*
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* <p>
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* The servlet container calls the <code>init</code> method exactly once
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* after instantiating the servlet. The <code>init</code> method must
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* complete successfully before the servlet can receive any requests.
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*
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* <p>
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* The servlet container cannot place the servlet into service if the
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* <code>init</code> method
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* <ol>
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* <li>Throws a <code>ServletException</code>
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* <li>Does not return within a time period defined by the Web server
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* </ol>
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*
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*
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* @param config
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* a <code>ServletConfig</code> object containing the servlet's
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* configuration and initialization parameters
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*
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* @exception ServletException
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* if an exception has occurred that interferes with the
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* servlet's normal operation
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*
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* @see UnavailableException
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* @see #getServletConfig
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*/
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public void init(ServletConfig config) throws ServletException;
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/**
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*
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* Returns a {@link ServletConfig} object, which contains initialization and
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* startup parameters for this servlet. The <code>ServletConfig</code>
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* object returned is the one passed to the <code>init</code> method.
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*
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* <p>
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* Implementations of this interface are responsible for storing the
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* <code>ServletConfig</code> object so that this method can return it. The
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* {@link GenericServlet} class, which implements this interface, already
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* does this.
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*
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* @return the <code>ServletConfig</code> object that initializes this
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* servlet
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*
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* @see #init
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*/
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public ServletConfig getServletConfig();
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/**
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* Called by the servlet container to allow the servlet to respond to a
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* request.
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*
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* <p>
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* This method is only called after the servlet's <code>init()</code> method
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* has completed successfully.
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*
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* <p>
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* The status code of the response always should be set for a servlet that
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* throws or sends an error.
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*
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*
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* <p>
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* Servlets typically run inside multithreaded servlet containers that can
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* handle multiple requests concurrently. Developers must be aware to
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* synchronize access to any shared resources such as files, network
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* connections, and as well as the servlet's class and instance variables.
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* More information on multithreaded programming in Java is available in <a
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* href
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* ="http://java.sun.com/Series/Tutorial/java/threads/multithreaded.html">
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* the Java tutorial on multi-threaded programming</a>.
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*
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*
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* @param req
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* the <code>ServletRequest</code> object that contains the
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* client's request
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*
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* @param res
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* the <code>ServletResponse</code> object that contains the
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* servlet's response
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*
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* @exception ServletException
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* if an exception occurs that interferes with the servlet's
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* normal operation
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*
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* @exception IOException
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* if an input or output exception occurs
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*/
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public void service(ServletRequest req, ServletResponse res)
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throws ServletException, IOException;
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/**
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* Returns information about the servlet, such as author, version, and
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* copyright.
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*
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* <p>
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* The string that this method returns should be plain text and not markup
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* of any kind (such as HTML, XML, etc.).
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*
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* @return a <code>String</code> containing servlet information
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*/
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public String getServletInfo();
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/**
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* Called by the servlet container to indicate to a servlet that the servlet
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* is being taken out of service. This method is only called once all
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* threads within the servlet's <code>service</code> method have exited or
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* after a timeout period has passed. After the servlet container calls this
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* method, it will not call the <code>service</code> method again on this
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* servlet.
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*
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* <p>
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* This method gives the servlet an opportunity to clean up any resources
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* that are being held (for example, memory, file handles, threads) and make
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* sure that any persistent state is synchronized with the servlet's current
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* state in memory.
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*/
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public void destroy();
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}
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