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The Amazon Web Services SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2011-2014 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.transform;

import com.amazonaws.AmazonClientException;
import com.amazonaws.AmazonServiceException;
import com.amazonaws.util.json.JSONException;
import com.amazonaws.util.json.JSONObject;

/**
 * Unmarshaller for JSON error responses from AWS services.
 */
public class JsonErrorUnmarshaller extends AbstractErrorUnmarshaller {

    public JsonErrorUnmarshaller() {}

    protected JsonErrorUnmarshaller(Class exceptionClass) {
        super(exceptionClass);
    }

    /**
     * Subclass should override the match(String, JSONObject) method to indicate
     * whether it represents the given error type, and unmarshall(JSONObject)
     * should never return null.
     */
    public AmazonServiceException unmarshall(JSONObject json) throws Exception {
        String message = parseMessage(json);
        String errorCode = parseErrorCode(json);

        if ((null == message || message.isEmpty()) && (null == errorCode || errorCode.isEmpty())) {
            /**
             * Trigger the catch block in AmazonHttpClient.handleErrorResponse to handle 413 and 503 errors
             */
            throw new AmazonClientException("Neither error message nor error code is found in the error response payload.");
        } else {
            AmazonServiceException ase = newException(message);
            ase.setErrorCode(errorCode);
            return ase;
        }
    }

    public String parseMessage(JSONObject json) throws Exception {
        return parseMember("message", json);
    }

    public String parseMember(String key, JSONObject json) throws JSONException {
        if (key == null || key.length() == 0) {
            return null;
        }

        String firstLetterUppercaseKey;
        String firstLetterLowercaseKey;

        firstLetterLowercaseKey = key.substring(0, 1).toLowerCase()
                + key.substring(1);

        firstLetterUppercaseKey = key.substring(0, 1).toUpperCase()
                + key.substring(1);

         String value = "";
         if (json.has(firstLetterUppercaseKey)) {
             value = json.getString(firstLetterUppercaseKey);
         } else if (json.has(firstLetterLowercaseKey)) {
             value = json.getString(firstLetterLowercaseKey);
         }

         return value;
    }

    public String parseErrorCode(JSONObject json) throws Exception {
        if (json.has("__type")) {
            String type = json.getString("__type");
            int separator = type.lastIndexOf("#");
            return type.substring(separator + 1);
        }

        return null;
    }

    /**
     * Any subclass that is specific to a error type should only return true
     * when the response matches, either by matching the error type parsed from
     * header or from the JSON content.
     * 
     * @param errorTypeFromHeader
     *            The error type parsed from the response headers, or null if
     *            such information is not available in the headers.
     * 
     * @param json
     *            The JSON content of the response. Subclass should check for
     *            the error type information from this JSONObject if
     *            errorTypeFromHeader is null.
     */
    public boolean match(String errorTypeFromHeader, JSONObject json) throws Exception {
        return true;
    }
}