/*
    * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/methods/ExpectContinueMethod.java,v 1.5.2.3 2004/02/22 18:21:15 olegk Exp $
    * $Revision: 1.5.2.3 $
    * $Date: 2004/02/22 18:21:15 $
    *
    * ====================================================================
    *
    *  Copyright 2003-2004 The Apache Software Foundation
    *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   * [Additional notices, if required by prior licensing conditions]
   *
   */
  
  package org.apache.commons.httpclient.methods;
  
  import java.io.IOException;
  import org.apache.commons.httpclient.HttpConnection;
  import org.apache.commons.httpclient.HttpException;
  import org.apache.commons.httpclient.HttpState;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /***
   * <p>
   * This abstract class serves as a foundation for all HTTP methods 
   * that support 'Expect: 100-continue' handshake.
   * </p>
   * 
   * <p>
   * The purpose of the 100 (Continue) status (refer to section 10.1.1 
   * of the RFC 2616 for more details) is to allow a client that is 
   * sending a request message with a request body to determine if the 
   * origin server is willing to accept the request (based on the request 
   * headers) before the client sends the request body. In some cases,
   * it might either be inappropriate or highly inefficient for the 
   * client to send the body if the server will reject the message 
   * without looking at the body.
   * </p>
   * 
   * <p>
   * 'Expect: 100-continue' handshake should be used with caution,
   * as it may cause problems with HTTP servers and proxies that
   * do not support HTTP/1.1 protocol.
   * </p>
   * 
   * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
   *
   * @since 2.0beta1
   */
  
  public abstract class ExpectContinueMethod extends GetMethod {
      
      /*** This flag specifies whether "expect: 100-continue" handshake is
       * to be used prior to sending the request body */
      private boolean useExpectHeader = false;
      
      /*** LOG object for this class. */
      private static final Log LOG = LogFactory.getLog(ExpectContinueMethod.class);
  
      /***
       * No-arg constructor.
       *
       * @since 2.0
       */
      public ExpectContinueMethod() {
          super();
      }
  
      /***
       * Constructor specifying a URI.
       *
       * @param uri either an absolute or relative URI
       *
       * @since 2.0
       */
      public ExpectContinueMethod(String uri) {
          super(uri);
      }
  
      /***
       * Constructor specifying a URI and a tempDir.
      *
      * @param uri either an absolute or relative URI
      * @param tempDir directory to store temp files in
      *
      * @deprecated the client is responsible for disk I/O
      * @since 2.0
      */
     public ExpectContinueMethod(String uri, String tempDir) {
         super(uri, tempDir);
     }
 
     /***
      * Constructor specifying a URI, tempDir and tempFile.
      *
      * @param uri either an absolute or relative URI
      * @param tempDir directory to store temp files in
      * @param tempFile file to store temporary data in
      *
      * @deprecated the client is responsible for disk I/O
      * @since 2.0
      */
     public ExpectContinueMethod(String uri, String tempDir, String tempFile) {
         super(uri, tempDir, tempFile);
     }
 
     /***
      * <p>
      * Returns <tt>true</tt> if the 'Expect: 100-Continue' handshake
      * is activated. The purpose of the 'Expect: 100-Continue' 
      * handshake to allow a client that is sending a request message 
      * with a request body to determine if the origin server is 
      * willing to accept the request (based on the request headers) 
      * before the client sends the request body.
      * </p>
      * 
      * @return <tt>true</tt> if 'Expect: 100-Continue' handshake is to
      * be used, <tt>false</tt> otherwise.
      * 
      * @since 2.0beta1
      */
     public boolean getUseExpectHeader() {
         return this.useExpectHeader;
     }
 
     /***
      * <p>
      * Activates 'Expect: 100-Continue' handshake. The purpose of 
      * the 'Expect: 100-Continue' handshake to allow a client that is 
      * sending a request message with a request body to determine if 
      * the origin server is willing to accept the request (based on 
      * the request headers) before the client sends the request body.
      * </p>
      * 
      * <p>
      * The use of the 'Expect: 100-continue' handshake can result in 
      * noticable peformance improvement for entity enclosing requests
      * (such as POST and PUT) that require the target server's 
      * authentication.
      * </p>
      * 
      * <p>
      * 'Expect: 100-continue' handshake should be used with 
      * caution, as it may cause problems with HTTP servers and 
      * proxies that do not support HTTP/1.1 protocol.
      * </p>
      * 
      * @param value boolean value
      * 
      * 
      * @since 2.0beta1
      */
     public void setUseExpectHeader(boolean value) {
         this.useExpectHeader = value;
     }
 
     /***
      * Returns <tt>true</tt> if there is a request body to be sent.
      * 'Expect: 100-continue' handshake may not be used if request
      * body is not present
      * 
      * @return boolean
      * 
      * @since 2.0beta1
      */
     protected abstract boolean hasRequestContent();
 
     /***
      * Sets the <tt>Expect</tt> header if it has not already been set, 
      * in addition to the "standard" set of headers.
      *
      * @param state the {@link HttpState state} information associated with this method
      * @param conn the {@link HttpConnection connection} used to execute
      *        this HTTP method
      *
      * @throws IOException if an I/O (transport) error occurs
      * @throws HttpException  if a protocol exception occurs.
      * @throws HttpRecoverableException if a recoverable transport error occurs. 
      *                    Usually this kind of exceptions can be recovered from by
      *                    retrying the HTTP method 
      */
     protected void addRequestHeaders(HttpState state, HttpConnection conn)
     throws IOException, HttpException {
         LOG.trace("enter ExpectContinueMethod.addRequestHeaders(HttpState, HttpConnection)");
         
         super.addRequestHeaders(state, conn);
         // If the request is being retried, the header may already be present
         boolean headerPresent = (getRequestHeader("Expect") != null);
         // See if the expect header should be sent
         // = HTTP/1.1 or higher
         // = request body present
 
         if (getUseExpectHeader() && isHttp11() && hasRequestContent()) {
             if (!headerPresent) {
                 setRequestHeader("Expect", "100-continue");
             }
         } else {
             if (headerPresent) {
                 removeRequestHeader("Expect");
             }
         }
     }
 }