Java tutorial
/* * Copyright 2010-2014 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.util.Map; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonParser; import com.amazonaws.AmazonWebServiceResponse; import com.amazonaws.ResponseMetadata; import com.amazonaws.internal.CRC32MismatchException; import com.amazonaws.transform.JsonUnmarshallerContext; import com.amazonaws.transform.Unmarshaller; import com.amazonaws.transform.VoidJsonUnmarshaller; import com.amazonaws.util.CRC32ChecksumCalculatingInputStream; /** * Default implementation of HttpResponseHandler that handles a successful * response from an AWS service and unmarshalls the result using a JSON * unmarshaller. * * @param <T> * Indicates the type being unmarshalled by this response handler. */ public class JsonResponseHandler<T> implements HttpResponseHandler<AmazonWebServiceResponse<T>> { /** The JSON unmarshaller to use when handling the response */ private Unmarshaller<T, JsonUnmarshallerContext> responseUnmarshaller; /** Shared logger for profiling information */ private static final Log log = LogFactory.getLog("com.amazonaws.request"); private static JsonFactory jsonFactory = new JsonFactory(); public boolean needsConnectionLeftOpen = false; /** * Constructs a new response handler that will use the specified JSON * unmarshaller to unmarshall the service response and uses the specified * response element path to find the root of the business data in the * service's response. * * @param responseUnmarshaller * The JSON unmarshaller to use on the response. */ public JsonResponseHandler(Unmarshaller<T, JsonUnmarshallerContext> responseUnmarshaller) { this.responseUnmarshaller = responseUnmarshaller; /* * Even if the invoked operation just returns null, we still need an * unmarshaller to run so we can pull out response metadata. * * We might want to pass this in through the client class so that we * don't have to do this check here. */ if (this.responseUnmarshaller == null) { this.responseUnmarshaller = new VoidJsonUnmarshaller<T>(); } } /** * @see com.amazonaws.http.HttpResponseHandler#handle(com.amazonaws.http.HttpResponse) */ public AmazonWebServiceResponse<T> handle(HttpResponse response) throws Exception { log.trace("Parsing service response JSON"); String CRC32Checksum = response.getHeaders().get("x-amz-crc32"); CRC32ChecksumCalculatingInputStream crc32ChecksumInputStream = null; JsonParser jsonParser = null; if (!needsConnectionLeftOpen) { if (CRC32Checksum != null) { crc32ChecksumInputStream = new CRC32ChecksumCalculatingInputStream(response.getContent()); jsonParser = jsonFactory.createParser(crc32ChecksumInputStream); } else { jsonParser = jsonFactory.createParser(response.getContent()); } } try { AmazonWebServiceResponse<T> awsResponse = new AmazonWebServiceResponse<T>(); JsonUnmarshallerContext unmarshallerContext = new JsonUnmarshallerContext(jsonParser, response); registerAdditionalMetadataExpressions(unmarshallerContext); T result = responseUnmarshaller.unmarshall(unmarshallerContext); if (CRC32Checksum != null) { long serverSideCRC = Long.parseLong(CRC32Checksum); long clientSideCRC = crc32ChecksumInputStream.getCRC32Checksum(); if (clientSideCRC != serverSideCRC) { throw new CRC32MismatchException( "Client calculated crc32 checksum didn't match that calculated by server side"); } } awsResponse.setResult(result); Map<String, String> metadata = unmarshallerContext.getMetadata(); metadata.put(ResponseMetadata.AWS_REQUEST_ID, response.getHeaders().get("x-amzn-RequestId")); awsResponse.setResponseMetadata(new ResponseMetadata(metadata)); log.trace("Done parsing service response"); return awsResponse; } finally { if (!needsConnectionLeftOpen) { try { jsonParser.close(); } catch (IOException e) { log.warn("Error closing json parser", e); } } } } /** * Hook for subclasses to override in order to collect additional metadata * from service responses. * * @param unmarshallerContext * The unmarshaller context used to process a service's response * data. */ protected void registerAdditionalMetadataExpressions(JsonUnmarshallerContext unmarshallerContext) { } /** * 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 needsConnectionLeftOpen; } }