org.opentravel.otm.forum2016.am.RESTClientOperation.java Source code

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Here is the source code for org.opentravel.otm.forum2016.am.RESTClientOperation.java

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/**
 * Copyright (C) 2016 OpenTravel Alliance (info@opentravel.org)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License 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 org.opentravel.otm.forum2016.am;

import java.io.IOException;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.CloseableHttpClient;

import com.google.gson.Gson;

/**
 * Base class that provides common functions related to the invocation of remote
 * REST API's.
 *
 * @param <R>  the type of the API response that will be returned by the operation
 * @author S. Livezey
 */
public abstract class RESTClientOperation<R> {

    protected static Gson gson = new Gson();

    private APIOperationFactory factory;

    /**
     * Constructor that assigns the factory that created this operation.
     * 
     * @param factory  the factory that created this operation
     */
    protected RESTClientOperation(APIOperationFactory factory) {
        this.factory = factory;
    }

    /**
     * Executes the API Manager request and returns the result.
     * 
     * @return R
     * @throws IOException  thrown if an error occurrs during execution of the request
     */
    public abstract R execute() throws IOException;

    /**
     * Unmarshalls the response payload stream to the Java return type for the operation.
     * 
     * @param response  the HTTP response to unmarshal
     * @return R
     * @throws IOException  thrown if an error occurrs during unmarshalling
     */
    protected abstract R unmarshallResponse(HttpResponse response) throws IOException;

    /**
     * Returns the API Manager security scope for this operation.
     * 
     * @return String
     */
    protected abstract String getSecurityScope();

    /**
     * Invokes the HTTP request using the OAuth2 credentials established by the factory.
     * 
     * @param request  the request to be executed
     * @return R
     * @throws IOException  thrown if an error occurrs during execution of the request
     */
    protected R execute(HttpUriRequest request) throws IOException {
        OAuth2AccessToken token = factory.getAccessToken(getSecurityScope());
        R responseObj = null;

        request.addHeader("Authorization", token.getTokenType() + " " + token.getAccessToken());

        try (CloseableHttpClient client = newHttpClient()) {
            HttpResponse response = client.execute(request);
            int statusCode = response.getStatusLine().getStatusCode();

            if ((statusCode >= 200) && (statusCode <= 299)) {
                responseObj = unmarshallResponse(response);

            } else {
                throw new IOException("Service invocation error [" + statusCode + "]:" + readPayload(response));
            }
            return responseObj;
        }
    }

    /**
     * Returns a new HTTP client instance for use with API Manager REST API invocations.
     * 
     * @return CloseableHttpClient
     * @throws IOException  thrown if an error occurs while constructing the HTTP client
     */
    protected CloseableHttpClient newHttpClient() throws IOException {
        return APIOperationFactory.newHttpClient();
    }

    /**
     * Returns the payload from the HTTP response as a string.  If no payload exists, this
     * method will return null.
     * 
     * @param response  the HTTP response to process
     * @return String
     * @throws IOException  thrown if an error occurrs while reading the response's entity stream
     */
    protected static String readPayload(HttpResponse response) throws IOException {
        return APIOperationFactory.readPayload(response);
    }

}