Translate.java

/*
 * Copyright 2012 Javier Pérez Pacheco and Francisco Díaz Rodriguez
 * TweetTopics 2.0
 * javielinux@gmail.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.javielinux.utils;

import android.util.Log;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

/**
 * Makes the Google Translate API available to Java applications.
 *
 * @author Richard Midwinter
 * @author Emeric Vernat
 * @author Juan B Cabral
 * @author Cedric Beust
 */
public class Translate {
    
    private static final String ENCODING = "UTF-8";
    private static final String URL_STRING = "http://ajax.googleapis.com/ajax/services/language/translate?v=1.0&langpair=";
    private static final String TEXT_VAR = "&q=";

    /**
     * Translates text from a given language to another given language using Google Translate
     *
     * @param text The String to translate.
     * @param from The language code to translate from.
     * @param to The language code to translate to.
     * @return The translated String.
     * @throws MalformedURLException
     * @throws IOException
     */
    public static String translate(String text, String from, String to) throws Exception {
            return retrieveTranslation(text, from, to);
    }

    /**
     * Forms an HTTP request and parses the response for a translation.
     *
     * @param text The String to translate.
     * @param from The language code to translate from.
     * @param to The language code to translate to.
     * @return The translated String.
     * @throws Exception
     */
    private static String retrieveTranslation(String text, String from, String to) throws Exception {
        try {
            StringBuilder url = new StringBuilder();
            url.append(URL_STRING).append(from).append("%7C").append(to);
            url.append(TEXT_VAR).append(URLEncoder.encode(text, ENCODING));

            Log.d(Utils.TAG, "Conectadndo a " + url.toString());
            HttpURLConnection uc = (HttpURLConnection) new URL(url.toString()).openConnection();
            uc.setDoInput(true);
            uc.setDoOutput(true);
            try {
                InputStream is= uc.getInputStream();
                String result = toString(is);
                
                JSONObject json = new JSONObject(result);
                return ((JSONObject)json.get("responseData")).getString("translatedText");
            } finally { // http://java.sun.com/j2se/1.5.0/docs/guide/net/http-keepalive.html
                uc.getInputStream().close();
                if (uc.getErrorStream() != null) uc.getErrorStream().close();
            }
        } catch (Exception ex) {
            throw ex;
        }
    }

    /**
     * Reads an InputStream and returns its contents as a String. Also effects rate control.
     * @param inputStream The InputStream to read from.
     * @return The contents of the InputStream as a String.
     * @throws Exception
     */
    private static String toString(InputStream inputStream) throws Exception {
        StringBuilder outputBuilder = new StringBuilder();
        try {
            String string;
            if (inputStream != null) {
                BufferedReader reader =
                        new BufferedReader(new InputStreamReader(inputStream, ENCODING));
                while (null != (string = reader.readLine())) {
                    outputBuilder.append(string).append('\n');
                }
            }
        } catch (Exception ex) {
            Log.e(Utils.TAG, "Error reading translation stream.", ex);
        }
        return outputBuilder.toString();
    }
}