Java tutorial
/** * GoogleAPI.java * * Copyright (C) 2009, Richard Midwinter * * This file is part of google-api-translate-java. * * google-api-translate-java is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * google-api-translate-java is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with google-api-translate-java. If not, see <http://www.gnu.org/licenses/>. */ package com.google.api; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.HttpURLConnection; import java.net.URL; import org.json.JSONObject; /** * Makes generic Google API functionality available to specific API classes. * * @author Richard Midwinter * @author Kramar Tomas */ public abstract class GoogleAPI { protected static final String ENCODING = "UTF-8"; /** * The HTTP referrer attribute. * * This allows Google to distinguish between programs. */ protected static String referrer; /** * Sets the HTTP Referrer. * @param pReferrer The HTTP referrer parameter. */ public static void setHttpReferrer(final String pReferrer) { referrer = pReferrer; } public static void validateReferrer() throws Exception { if (referrer == null || referrer.length() == 0) { throw new Exception("[google-api-translate-java] Referrer is not set. Call setHttpReferrer()."); } } /** * Forms an HTTP request, sends it using GET method and returns the result of the request as a JSONObject. * * @param url The URL to query for a JSONObject. * @return The translated String. * @throws Exception on error. */ protected static JSONObject retrieveJSON(final URL url) throws Exception { try { final HttpURLConnection uc = (HttpURLConnection) url.openConnection(); uc.setRequestProperty("referer", referrer); uc.setRequestMethod("GET"); uc.setDoOutput(true); try { final String result = inputStreamToString(uc.getInputStream()); return new JSONObject(result); } 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 new Exception("[google-api-translate-java] Error retrieving translation.", ex); } } /** * Forms an HTTP request, sends it using POST method and returns the result of the request as a JSONObject. * * @param url The URL to query for a JSONObject. * @param parameters Additional POST parameters * @return The translated String. * @throws Exception on error. */ protected static JSONObject retrieveJSON(final URL url, final String parameters) throws Exception { try { final HttpURLConnection uc = (HttpURLConnection) url.openConnection(); uc.setRequestProperty("referer", referrer); uc.setRequestMethod("POST"); uc.setDoOutput(true); final PrintWriter pw = new PrintWriter(uc.getOutputStream()); pw.write(parameters); pw.flush(); try { final String result = inputStreamToString(uc.getInputStream()); return new JSONObject(result); } 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(); } pw.close(); } } catch (Exception ex) { throw new Exception("[google-api-translate-java] Error retrieving translation.", 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 on error. */ private static String inputStreamToString(final InputStream inputStream) throws Exception { final 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) { throw new Exception("[google-api-translate-java] Error reading translation stream.", ex); } return outputBuilder.toString(); } }