com.ibm.watson.developer_cloud.util.ResponseUtil.java Source code

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Here is the source code for com.ibm.watson.developer_cloud.util.ResponseUtil.java

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/**
 * Copyright 2015 IBM Corp. 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.
 * 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.ibm.watson.developer_cloud.util;

import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.ParseException;
import org.apache.http.util.EntityUtils;

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

/**
 * Utility class to manage service responses.
 *
 * @author German Attanasio Ruiz (germanatt@us.ibm.com)
 * @see org.apache.http.HttpResponse HttpResponse
 */
public class ResponseUtil {

    /** The Constant log. */
    private static final Logger log = Logger.getLogger(ResponseUtil.class.getName());

    /** The Constant BUFFER_SIZE. */
    public static final int BUFFER_SIZE = 8192; // 8 kb

    /**
     * Return a {@link JsonElement} representation of the response.
     * 
     * @param response
     *            the HttpResponse
     * @return the content body as JSON
     * @throws IOException
     *             Signals that an I/O exception has occurred.
     */
    public static JsonElement getJsonElement(HttpResponse response) throws IOException {
        final String json = getString(response);
        if (json == null || json.length() == 0)
            throw new IOException("JSON response is empty");

        JsonElement element = new JsonParser().parse(json);
        return element;
    }

    /**
     * Returns a {@link JsonObject} representation of the response.
     *
     * @param response            an HTTP response
     * @return the content body as JSONArray
     * @throws IOException  If an input or output
     *                   exception occurred
     */
    public static JsonObject getJsonObject(HttpResponse response) throws IOException {
        return getJsonElement(response).getAsJsonObject();
    }

    /**
     * Returns a String representation of the response.
     * 
     * @param response
     *            an HTTP response
     * @return the content body as String
     * @throws IOException
     *             network error
     * */
    public static String getString(HttpResponse response) throws IOException {
        HttpEntity entity;
        try {
            entity = response.getEntity();
            if (entity == null)
                return null;
            else
                return EntityUtils.toString(entity, "UTF-8");
        } catch (ParseException e) {
            log.log(Level.SEVERE, "Could not parse service response", e);
            throw new IOException("Could not parse service response:" + e.getMessage());
        } catch (IOException e) {
            log.log(Level.SEVERE, "Could not read service response", e);
            throw new IOException("Could not read service response:" + e.getMessage());
        }
    }

    /**
     * Returns a String representation of the response.
     * 
     * @param response
     *            an HTTP response
     * @return the content body as String
     * @throws IOException
     *             network error
     * */
    public static InputStream getInputStream(HttpResponse response) throws IOException {
        InputStream is;
        try {
            is = response.getEntity().getContent();
            if (is == null)
                return null;
        } catch (IOException e) {
            log.log(Level.SEVERE, "Could not read service response", e);
            throw new IOException("Could not read service response:" + e.getMessage());
        }
        return is;
    }

    /**
     * Returns <T> after parsing the string response.
     *
     * @param <T> the generic type to use when parsing the response
     * @param response the http response
     * @param type the type of the response 
     * @return the object
     * @throws IOException Signals that an I/O exception has occurred.
     */
    public static <T> T getObject(HttpResponse response, Class<T> type) throws IOException {
        String jsonString = getString(response);

        T pojo = (T) GsonSingleton.getGson().fromJson(jsonString, type);
        return pojo;
    }

}