HttpRequestFactory.java

/*
 * Copyright 2011-2015 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 com.amazonaws.AmazonClientException;
import com.amazonaws.ClientConfiguration;
import com.amazonaws.Request;
import com.amazonaws.util.HttpUtils;
import com.amazonaws.util.StringUtils;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.net.URI;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Responsible for creating Http request objects from AWS {@link Request}s.
 */
class HttpRequestFactory {

    private static final String DEFAULT_ENCODING = "UTF-8";

    /**
     * Creates an HttpClient method object based on the specified request and
     * populates any parameters, headers, etc. from the original request.
     *
     * @param request The request to convert to an HttpClient method object.
     * @param context The execution context of the HTTP method to be executed
     * @return The converted HttpClient method object with any parameters,
     *         headers, etc. from the original request set.
     */
    HttpRequest createHttpRequest(Request<?> request, ClientConfiguration clientConfiguration,
            ExecutionContext context) {
        URI endpoint = request.getEndpoint();

        /*
         * HttpClient cannot handle url in pattern of "http://host//path", so we
         * have to escape the double-slash between endpoint and resource-path
         * into "/%2F"
         */
        String uri = HttpUtils.appendUri(endpoint.toString(), request.getResourcePath(), true);
        String encodedParams = HttpUtils.encodeParameters(request);

        /*
         * For all non-POST requests, and any POST requests that already have a
         * payload, we put the encoded params directly in the URI, otherwise,
         * we'll put them in the POST request's payload.
         */
        boolean requestHasNoPayload = request.getContent() != null;
        boolean requestIsPost = request.getHttpMethod() == HttpMethodName.POST;
        boolean putParamsInUri = !requestIsPost || requestHasNoPayload;
        if (encodedParams != null && putParamsInUri) {
            uri += "?" + encodedParams;
        }

        InputStream is = request.getContent();

        String method = request.getHttpMethod().toString();
        if (method.equals("POST")) {
            /*
             * If there isn't any payload content to include in this request,
             * then try to include the POST parameters in the query body,
             * otherwise, just use the query string. For all AWS Query services,
             * the best behavior is putting the params in the request body for
             * POST requests, but we can't do that for S3.
             */
            if (request.getContent() == null && encodedParams != null) {
                is = new ByteArrayInputStream(encodedParams.getBytes(StringUtils.UTF8));
                request.addHeader("Content-Length", String.valueOf(encodedParams.length()));
            }
        }

        String len = request.getHeaders().get("Content-Length");
        if (len == null || len.isEmpty()) {
            if (is != null) {
                throw new AmazonClientException("Unknown content-length");
            } else {
                request.addHeader("Content-Length", "0");
            }
        }

        /*
         * Amazon DynamoDB sets CRC32 checksum in the header 'x-amz-crc32'. If
         * compression is turned on, then the checksum is calculated on the
         * compressed data. On the client side, compression is handled by the
         * HTTP client. In most cases, the client doesn't have access to
         * compressed data, so there is no way to compute the checksum of
         * compressed data unless the client compress it. To get around it,
         * compression is turned off explicitly.
         */
        if (request.getHeaders().get("Accept-Encoding") == null) {
            request.addHeader("Accept-Encoding", "identity");
        }

        Map<String, String> headers = new HashMap<String, String>();
        configureHeaders(headers, request, context, clientConfiguration);

        return new HttpRequest(method, URI.create(uri), headers, is);
    }

    /** Configures the headers in the specified Apache HTTP request. */
    private void configureHeaders(Map<String, String> headers, Request<?> request,
            ExecutionContext context, ClientConfiguration clientConfiguration) {
        /*
         * Apache HttpClient omits the port number in the Host header (even if
         * we explicitly specify it) if it's the default port for the protocol
         * in use. To ensure that we use the same Host header in the request and
         * in the calculated string to sign (even if Apache HttpClient changed
         * and started honoring our explicit host with endpoint), we follow this
         * same behavior here and in the QueryString signer.
         */
        URI endpoint = request.getEndpoint();
        String hostHeader = endpoint.getHost();
        if (HttpUtils.isUsingNonDefaultPort(endpoint)) {
            hostHeader += ":" + endpoint.getPort();
        }
        headers.put("Host", hostHeader);

        // Copy over any other headers already in our request
        for (Entry<String, String> entry : request.getHeaders().entrySet()) {
            headers.put(entry.getKey(), entry.getValue());
        }

        /* Set content type and encoding */
        if (headers.get("Content-Type") == null || headers.get("Content-Type").isEmpty()) {
            headers.put("Content-Type",
                    "application/x-www-form-urlencoded; " +
                            "charset=" + DEFAULT_ENCODING.toLowerCase());
        }

        // Override the user agent string specified in the client params if the
        // context requires it
        if (context != null && context.getContextUserAgent() != null) {
            headers.put("User-Agent",
                    createUserAgentString(clientConfiguration, context.getContextUserAgent()));
        }
    }

    /**
     * Appends the given user-agent string to the client's existing one and
     * returns it.
     */
    private String createUserAgentString(ClientConfiguration clientConfiguration,
            String contextUserAgent) {
        if (clientConfiguration.getUserAgent().contains(contextUserAgent)) {
            return clientConfiguration.getUserAgent();
        } else {
            return clientConfiguration.getUserAgent() + " " + contextUserAgent;
        }
    }

}