Java tutorial
/* * Copyright 2010-2019 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.SdkClientException; 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; import static com.amazonaws.http.AmazonHttpClient.HEADER_SDK_TRANSACTION_ID; /** * 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<AmazonServiceException> { private static final Log log = LogFactory.getLog(DefaultErrorResponseHandler.class); /** * The list of error response unmarshallers to try to apply to error responses. */ private List<Unmarshaller<AmazonServiceException, Node>> 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<Unmarshaller<AmazonServiceException, Node>> unmarshallerList) { this.unmarshallerList = unmarshallerList; } @Override public AmazonServiceException handle(HttpResponse errorResponse) throws Exception { AmazonServiceException ase = createAse(errorResponse); if (ase == null) { throw new SdkClientException("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 = documentFromContent(errorResponse.getContent(), idString(errorResponse)); /* * 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<AmazonServiceException, Node> unmarshaller : unmarshallerList) { AmazonServiceException ase = unmarshaller.unmarshall(document); if (ase != null) { ase.setStatusCode(errorResponse.getStatusCode()); return ase; } } return null; } private Document documentFromContent(InputStream content, String idString) throws ParserConfigurationException, SAXException, IOException { try { return parseXml(contentToString(content, idString), idString); } catch (Exception 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("<empty/>"); } } private String contentToString(InputStream content, String idString) throws Exception { try { return IOUtils.toString(content); } catch (Exception e) { log.debug(String.format("Unable to read input stream to string (%s)", idString), e); throw e; } } private Document parseXml(String xml, String idString) throws Exception { try { return XpathUtils.documentFrom(xml); } catch (Exception e) { log.debug(String.format("Unable to parse HTTP response (%s) content to XML document '%s' ", idString, xml), e); throw e; } } private String idString(HttpResponse errorResponse) { StringBuilder idString = new StringBuilder(); try { if (errorResponse.getRequest().getHeaders().containsKey(HEADER_SDK_TRANSACTION_ID)) { idString.append("Invocation Id:") .append(errorResponse.getRequest().getHeaders().get(HEADER_SDK_TRANSACTION_ID)); } if (errorResponse.getHeaders().containsKey(X_AMZN_REQUEST_ID_HEADER)) { if (idString.length() > 0) { idString.append(", "); } idString.append("Request Id:").append(errorResponse.getHeaders().get(X_AMZN_REQUEST_ID_HEADER)); } } catch (NullPointerException npe) { log.debug("Error getting Request or Invocation ID from response", npe); } return idString.length() > 0 ? idString.toString() : "Unknown"; } /** * 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; } }