defaulthttpmethodretryhandler.java

Light in the box 抓取程序。 使用HttpClient

/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/DefaultHttpMethodRetryHandler.java,v 1.3 2004/12/20 11:47:46 olegk Exp $
 * $Revision: 480424 $
 * $Date: 2006-11-29 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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/>.
 *
 */

package org.apache.commons.httpclient;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.NoRouteToHostException;
import java.net.UnknownHostException;

/**
 * The default {@link HttpMethodRetryHandler} used by {@link HttpMethod}s.
 * 
 * @author Michael Becke
 * @author <a href="mailto:oleg -at- ural.ru">Oleg Kalnichevski</a>
 */
public class DefaultHttpMethodRetryHandler implements HttpMethodRetryHandler {


    private static Class SSL_HANDSHAKE_EXCEPTION = null;
    
    static {
        try {
            SSL_HANDSHAKE_EXCEPTION = Class.forName("javax.net.ssl.SSLHandshakeException");
        } catch (ClassNotFoundException ignore) {           
        }
    }
    /** the number of times a method will be retried */
    private int retryCount;
    
    /** Whether or not methods that have successfully sent their request will be retried */
    private boolean requestSentRetryEnabled;
    
    /**
     * Creates a new DefaultHttpMethodRetryHandler.
     * @param retryCount the number of times a method will be retried
     * @param requestSentRetryEnabled if true, methods that have successfully sent their request will be retried
     */
    public DefaultHttpMethodRetryHandler(int retryCount, boolean requestSentRetryEnabled) {
        super();
        this.retryCount = retryCount;
        this.requestSentRetryEnabled = requestSentRetryEnabled;
    }
    
    /**
     * Creates a new DefaultHttpMethodRetryHandler that retries up to 3 times
     * but does not retry methods that have successfully sent their requests.
     */
    public DefaultHttpMethodRetryHandler() {
        this(3, false);
    }
    /** 
     * Used <code>retryCount</code> and <code>requestSentRetryEnabled</code> to determine
     * if the given method should be retried.
     * 
     * @see HttpMethodRetryHandler#retryMethod(HttpMethod, IOException, int)
     */
    public boolean retryMethod(
        final HttpMethod method, 
        final IOException exception, 
        int executionCount) {
        if (method == null) {
            throw new IllegalArgumentException("HTTP method may not be null");
        }
        if (exception == null) {
            throw new IllegalArgumentException("Exception parameter may not be null");
        }
        // HttpMethod interface is the WORST thing ever done to HttpClient
        if (method instanceof HttpMethodBase) {
            if (((HttpMethodBase)method).isAborted()) {
                return false;
            }
        }
        if (executionCount > this.retryCount) {
            // Do not retry if over max retry count
            return false;
        }
        if (exception instanceof NoHttpResponseException) {
            // Retry if the server dropped connection on us
            return true;
        }
        if (exception instanceof InterruptedIOException) {
            // Timeout
            return false;
        }
        if (exception instanceof UnknownHostException) {
            // Unknown host
            return false;
        }
        if (exception instanceof NoRouteToHostException) {
            // Host unreachable
            return false;
        }
        if (SSL_HANDSHAKE_EXCEPTION != null && SSL_HANDSHAKE_EXCEPTION.isInstance(exception)) {
            // SSL handshake exception
            return false;
        }
        if (!method.isRequestSent() || this.requestSentRetryEnabled) {
            // Retry if the request has not been sent fully or
            // if it's OK to retry methods that have been sent
            return true;
        }
        // otherwise do not retry
        return false;
    }
    
    /**
     * @return <code>true</code> if this handler will retry methods that have 
     * successfully sent their request, <code>false</code> otherwise
     */
    public boolean isRequestSentRetryEnabled() {
        return requestSentRetryEnabled;
    }

    /**
     * @return the maximum number of times a method will be retried
     */
    public int getRetryCount() {
        return retryCount;
    }
}