com.amazonaws.http.DefaultErrorResponseHandler Maven / Gradle / Ivy

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/*
 * Copyright 2010-2016 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.AmazonServiceException;
import com.amazonaws.annotation.SdkProtectedApi;
import com.amazonaws.transform.Unmarshaller;
import com.amazonaws.util.IOUtils;
import com.amazonaws.util.StringUtils;
import com.amazonaws.util.XpathUtils;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import javax.xml.parsers.ParserConfigurationException;

/**
 * Implementation of HttpResponseHandler that handles only error responses from Amazon Web Services.
 * A list of unmarshallers is passed into the constructor, and while handling a response, each
 * unmarshaller is tried, in order, until one is found that can successfully unmarshall the error
 * response.  If no unmarshaller is found that can unmarshall the error response, a generic
 * AmazonServiceException is created and populated with the AWS error response information (error
 * message, AWS error code, AWS request ID, etc).
 */
@SdkProtectedApi
public class DefaultErrorResponseHandler implements HttpResponseHandler {
    private static final Log log = LogFactory.getLog(DefaultErrorResponseHandler.class);

    /**
     * The list of error response unmarshallers to try to apply to error responses.
     */
    private List> unmarshallerList;

    /**
     * Constructs a new DefaultErrorResponseHandler that will handle error responses from Amazon
     * services using the specified list of unmarshallers. Each unmarshaller will be tried, in
     * order, until one is found that can unmarshall the error response.
     *
     * @param unmarshallerList The list of unmarshallers to try using when handling an error
     *                         response.
     */
    public DefaultErrorResponseHandler(
            List> unmarshallerList) {
        this.unmarshallerList = unmarshallerList;
    }

    @Override
    public AmazonServiceException handle(HttpResponse errorResponse) throws Exception {
        AmazonServiceException ase = createAse(errorResponse);
        if (ase == null) {
            throw new AmazonClientException("Unable to unmarshall error response from service");
        }
        ase.setHttpHeaders(errorResponse.getHeaders());
        if (StringUtils.isNullOrEmpty(ase.getErrorCode())) {
            ase.setErrorCode(errorResponse.getStatusCode() + " " + errorResponse.getStatusText());
        }
        return ase;
    }

    private AmazonServiceException createAse(HttpResponse errorResponse) throws Exception {
        // Try to parse the error response as XML
        final Document document = parseContentAsXml(errorResponse.getContent());

        /*
         * We need to select which exception unmarshaller is the correct one to
         * use from all the possible exceptions this operation can throw.
         * Currently we rely on the unmarshallers to return null if they can't
         * unmarshall the response, but we might need something a little more
         * sophisticated in the future.
         */
        for (Unmarshaller unmarshaller : unmarshallerList) {
            AmazonServiceException ase = unmarshaller.unmarshall(document);
            if (ase != null) {
                ase.setStatusCode(errorResponse.getStatusCode());
                return ase;
            }
        }
        return null;
    }

    private Document parseContentAsXml(InputStream content) throws ParserConfigurationException,
                                                                   SAXException, IOException {
        try {
            return XpathUtils.documentFrom(IOUtils.toString(content));
        } catch (Exception e) {
            log.info("Unable to parse HTTP response content.", e);
            // Generate an empty document to make the unmarshallers happy. Ultimately the default
            // unmarshaller will be called to unmarshall into the service base exception.
            return XpathUtils.documentFrom("");
        }
    }

    /**
     * Since this response handler completely consumes all the data from the underlying HTTP
     * connection during the handle method, we don't need to keep the HTTP connection open.
     *
     * @see com.amazonaws.http.HttpResponseHandler#needsConnectionLeftOpen()
     */
    public boolean needsConnectionLeftOpen() {
        return false;
    }

}