Android example source code file (Translate.java)

This example Android source code file (Translate.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, bufferedreader, connecting, encoding, error, exception, httpurlconnection, inputstream, inputstreamreader, io, jsonobject, net, network, string, stringbuilder, text_var, url_string, utf-8, utilities, utils

The Translate.java Android example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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.beust.android.translate;

import android.util.Log;

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;

import org.json.JSONObject;

/**
 * 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(TranslateService.TAG, "Connecting to " + url.toString());
            HttpURLConnection uc = (HttpURLConnection) new URL(url.toString()).openConnection();
            uc.setDoInput(true);
            uc.setDoOutput(true);
            try {
                Log.d(TranslateService.TAG, "getInputStream()");
                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(TranslateService.TAG, "Error reading translation stream.", ex);
        }
        return outputBuilder.toString();
    }
}