com.seleritycorp.context.RequestResponseHandler.java Source code

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Here is the source code for com.seleritycorp.context.RequestResponseHandler.java

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/*
 * Copyright (C) 2017 Selerity, Inc. (support@seleritycorp.com)
 *
 * 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 com.seleritycorp.context;

import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

/**
 * Parses query response to JsonObject, or upon error extracts descriptive error message.
 */
public class RequestResponseHandler implements org.apache.http.client.ResponseHandler<JsonObject> {
    private static final Log log = LogFactory.getLog(RequestResponseHandler.class);

    @Override
    public JsonObject handleResponse(HttpResponse response) throws ClientProtocolException, IOException {
        StatusLine statusLine = response.getStatusLine();
        int statusCode = statusLine.getStatusCode();
        HttpEntity entity = response.getEntity();
        String responseString = EntityUtils.toString(entity);
        JsonParser parser = new JsonParser();

        // The API does not return partials or some such, so any response that is not a 200,
        // indicates issues.
        if (statusCode != 200) {
            log.trace("Raw response: " + responseString);
            String errorMessage = statusCode + " " + statusLine.getReasonPhrase();
            // Instead of the pure HTTP status information, we try to get a descriptive error
            // message. Context API returns JSON objects that indicate the error. So we
            // opportunistically parse the content and drill down to get the error message. 
            try {
                JsonObject json = parser.parse(responseString).getAsJsonObject();
                String hint = "";

                if (json.has("errorCode")) {
                    hint = json.toString();
                } else if (json.has("errorMessage")) {
                    hint = json.get("errorMessage").getAsString();
                }

                if (hint != null && !hint.isEmpty()) {
                    errorMessage += ". (" + hint + ")";
                }
            } catch (Exception e) {
                // Extracting a more detailed error message failed. So we move forward with only the
                // HTTP status line.
            }
            throw new ClientProtocolException("Server responded with " + errorMessage);
        }

        // At this point, response has a 200 HTTP status code.

        String contentType = entity.getContentType().getValue();
        String parameterlessContentType = contentType.split("[; ]", 2)[0];
        if (!"application/json".equals(parameterlessContentType)) {
            // Response is not Json
            log.trace("Raw response: " + responseString);
            throw new ClientProtocolException(
                    "Received content type '" + contentType + "' instead of 'application/json'");
        }

        // At this point, response got sent as JSON

        // Parse the string to JSON
        JsonObject ret = parser.parse(responseString).getAsJsonObject();
        return ret;
    }
}