RepeatableInputStreamRequestEntity.java

/*
 * Copyright 2010 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 * 
 *  http://aws.amazon.com/apache2.0
 * 
 * or in the "license" file accompanying this file. This file 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.
 */
package com.amazonaws.http;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.httpclient.methods.InputStreamRequestEntity;
import org.apache.commons.httpclient.methods.RequestEntity;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Custom implementation of {@link RequestEntity} that delegates to an
 * {@link InputStreamRequestEntity}, with the one notable difference, that if
 * the underlying InputStream supports being reset, this RequestEntity will
 * report that it is repeatable and will reset the stream on all subsequent
 * attempts to write out the request.
 */
class RepeatableInputStreamRequestEntity implements RequestEntity {

    /** True if the request entity hasn't been written out yet */
    private boolean firstAttempt = true;
    
    /** The underlying InputStreamRequestEntity being delegated to */ 
    private InputStreamRequestEntity inputStreamRequestEntity;
    
    /** The InputStream containing the content to write out */
    private InputStream content;
    
    /** Shared logger for more debugging information */
    private static final Log log = LogFactory.getLog(HttpClient.class);


    /**
     * Creates a new RepeatableInputStreamRequestEntity using the information
     * from the specified request. If the input stream containing the request's
     * contents is repeatable, then this RequestEntity will report as being
     * repeatable.
     * 
     * @param request
     *            The details of the request being written out (content type,
     *            content length, and content).
     */
    RepeatableInputStreamRequestEntity(HttpRequest request) {
        /*
         * If we don't specify a content length when we instantiate our
         * InputStreamRequestEntity, then HttpClient will attempt to
         * buffer the entire stream contents into memory to determine
         * the content length. 
         * 
         * TODO: It'd be nice to have easier access to content length and 
         *       content type from the request, instead of having to look
         *       directly into the headers.
         */
        long contentLength = InputStreamRequestEntity.CONTENT_LENGTH_AUTO;
        try {
            String contentLengthString = request.getHeaders().get("Content-Length");
            if (contentLengthString != null) {
                contentLength = Long.parseLong(contentLengthString);
            }
        } catch (NumberFormatException nfe) {
            log.warn("Unable to parse content length from request.  " +
            		"Buffering contents in memory.");
        }

        String contentType = request.getHeaders().get("Content-Type");
        
        inputStreamRequestEntity = new InputStreamRequestEntity(
                request.getContent(), contentLength, contentType);
        content = request.getContent();
    }
    
    /**
     * Delegates to the underlying InputStreamRequestEntity.
     *  
     * @see org.apache.commons.httpclient.methods.RequestEntity#getContentType()
     */
    public String getContentType() {
        return inputStreamRequestEntity.getContentType();
    }

    /**
     * Returns true if the underlying InputStream supports marking/reseting or
     * if the underlying InputStreamRequestEntity is repeatable (i.e. its
     * content length has been set to
     * {@link InputStreamRequestEntity#CONTENT_LENGTH_AUTO} and therefore its
     * entire contents will be buffered in memory and can be repeated).
     * 
     * @see org.apache.commons.httpclient.methods.RequestEntity#isRepeatable()
     */
    public boolean isRepeatable() {
        return content.markSupported() || inputStreamRequestEntity.isRepeatable();
    }

    /**
     * Resets the underlying InputStream if this isn't the first attempt to
     * write out the request, otherwise simply delegates to
     * InputStreamRequestEntity to write out the data.
     * 
     * @see org.apache.commons.httpclient.methods.RequestEntity#writeRequest(java.io.OutputStream)
     */
    public void writeRequest(OutputStream output) throws IOException {
        if (!firstAttempt && isRepeatable()) {
            content.reset();
        }
        
        firstAttempt = false;
        inputStreamRequestEntity.writeRequest(output);
    }

    /**
     * Delegates to the underlying InputStreamRequestEntity.
     * 
     * @see org.apache.commons.httpclient.methods.RequestEntity#getContentLength()
     */
    public long getContentLength() {
        return inputStreamRequestEntity.getContentLength();
    }

}