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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 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.transform;

import java.lang.reflect.Constructor;

import org.w3c.dom.Node;

import com.amazonaws.AmazonServiceException;
import com.amazonaws.AmazonServiceException.ErrorType;
import com.amazonaws.util.XpathUtils;

/**
 * Unmarshalls an AWS error response into an AmazonServiceException, or
 * optionally, a subclass of AmazonServiceException if this class is extended.
 */
public class LegacyErrorUnmarshaller implements Unmarshaller {
    /**
     * The type of AmazonServiceException that will be instantiated. Subclasses
     * specialized for a specific type of exception can control this through the
     * protected constructor.
     */
    private final Class exceptionClass;

    /**
     * Constructs a new unmarshaller that will unmarshall AWS error responses as
     * a generic AmazonServiceException object.
     */
    public LegacyErrorUnmarshaller() {
        this(AmazonServiceException.class);
    }

    /**
     * Constructor allowing subclasses to specify a specific type of
     * AmazonServiceException to instantiating when populating the exception
     * object with data from the AWS error response.
     *
     * @param exceptionClass
     *            The class of AmazonServiceException to create and populate
     *            when unmarshalling the AWS error response.
     */
    protected LegacyErrorUnmarshaller(Class exceptionClass) {
        this.exceptionClass = exceptionClass;
    }

    /* (non-Javadoc)
     * @see com.amazonaws.transform.Unmarshaller#unmarshall(java.lang.Object)
     */
    public AmazonServiceException unmarshall(Node in) throws Exception {
        String errorCode = parseErrorCode(in);
        String message = XpathUtils.asString("Response/Errors/Error/Message", in);
        String requestId = XpathUtils.asString("Response/RequestID", in);
        String errorType = XpathUtils.asString("Response/Errors/Error/Type", in);

        Constructor constructor = exceptionClass.getConstructor(String.class);
        AmazonServiceException ase = constructor.newInstance(message);
        ase.setErrorCode(errorCode);
        ase.setRequestId(requestId);

        if (errorType == null) {
            ase.setErrorType(ErrorType.Unknown);
        } else if (errorType.equalsIgnoreCase("server")) {
            ase.setErrorType(ErrorType.Service);
        } else if (errorType.equalsIgnoreCase("client")) {
            ase.setErrorType(ErrorType.Client);
        }

        return ase;
    }

    /**
     * Returns the AWS error code for the specified error response.
     *
     * @param in
     *            The DOM tree node containing the error response.
     *
     * @return The AWS error code contained in the specified error response.
     *
     * @throws Exception
     *             If any problems were encountered pulling out the AWS error
     *             code.
     */
    public String parseErrorCode(Node in) throws Exception {
        return XpathUtils.asString("Response/Errors/Error/Code", in);
    }

    /**
     * Returns the path to the specified property within an error response.
     *
     * @param property
     *            The name of the desired property.
     *
     * @return The path to the specified property within an error message.
     */
    public String getErrorPropertyPath(String property) {
        return "Response/Errors/Error/" + property;
    }

}