Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 2

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1 Table of Contents Advanced Web Technology 13) Google Web Toolkits 2 - GWT, Communication Emmanuel Benoist Fall Term Internationalization Static String i18n Remote Procedure Code JSON Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 1 Internationalization Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 2 Internationalization : I18N Module Core types related to internationalization: LocaleInfo Provides information about the current locale. Constants Useful for localizing typed constant values Messages Useful for localizing messages requiring arguments ConstantsWithLookup Like Constants but with extra lookup flexibility for highly data-driven applications Dictionary Useful when adding a GWT module to existing localized web pages Localizable Useful for localizing algorithms encapsulated in a class or when the classes above don t provide sufficient control DateTimeFormat Formatting dates as strings. See the section on date and number formatting. NumberFormat Formatting numbers as strings. See the section on date and number formatting. Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 3 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 4

2 Static String i18n Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 5 Implement the Constants Interface Create the StockWatcherConstants interface Uses annotations for the default translation Implements the Constant interface (GWT) Bound automatically to the StockWatcherConstants*.properties files The java file must contain one method for each of the constants in the properties files The right value is found at runtime, corresponding to the locale Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 7 Interantionalizing Strings Implement the Constant Interface Contains only static strings Very efficient and compiled once. Implement the Messages Interface Allows to insert values in the string For instance numbers or dates Equivalent to the resource bundle in applications. Dynamic String Internationalization The Dictionary class lets your GWT application consume strings supplied by the host HTML page. Convenient if your existing web server has a localization system that you do not wish to integrate with the static string internationalization methods. Implement the Localizable Interface The most powerful technique allows you to go beyond simple string substitution create localized versions of custom types. Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 6 Example: the Constants file import com.google.gwt.i18n.client.constants; public interface StockWatcherConstants extends Constants StockWatcher ) String Symbol ) String Price ) String Change ) String Remove ) String Add ) String add(); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 8

3 Translate it to German Implement the Messages interface Create a file StockWatcherConstants de.properties stockwatcher = Aktienbeobachter symbol = Symbol price = Kurs change = Änderung remove = Entfernen add = Hinzufügen For Strings containing information Similar to resource bundles in Java Can contain strings with parameters {0 ist kein gültiges Aktiensymbol. The number is a place holder mystring = First parm is {0, second parm is {1, third parm is {2. Usefull for integrating dates, prices, internationalized results Usefull but less efficient. The strings must be produced at runtime Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 9 Messages file Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 10 The corresponding properties file import com.google.gwt.i18n.client.messages; import java.util.date; public interface StockWatcherMessages extends Messages {0 is not a valid symbol. ) String invalidsymbol(string symbol); StockWatcherMessages de.properties file. lastupdate = Letzte Aktualisierung: {0,date,medium {0,time, medium invalidsymbol = {0 ist kein gültiges Last update: {0,date,medium {0,time, medium ) String lastupdate(date timestamp); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 11 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 12

4 Replace content Replace content (Cont) Replace the texts with place holders <body> <img src= images/googlecode.png /> <h1 id= apptitle ></h1> Replacing strings set programmatically Create the instances of the classes (internationalized) private ArrayList<String> stocks = new ArrayList<String>(); private StockWatcherConstants constants = GWT.create( StockWatcherConstants.class); private StockWatcherMessages messages = GWT.create( StockWatcherMessages.class); Set the content: // Set the window title, the header text, and the Add button text. Window.setTitle(constants.stockWatcher()); RootPanel.get( apptitle ).add(new Label(constants. stockwatcher())); addstockbutton = new Button(constants.add()); // Create table for stock data. stocksflextable.settext(0, 0, constants.symbol()); stocksflextable.settext(0, 1, constants.price()); stocksflextable.settext(0, 2, constants.change()); stocksflextable.settext(0, 3, constants.remove()); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 13 Add a supported locale: Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 14 Client Server Communication Inside StockWatcher.gwt.xml add the property <entry point class= com.google.gwt.sample. stockwatcher.client.stockwatcher /> <extend property name= locale values= de /> </module> Load the german version by adding &locale=de Remote Procedure Code From Java To Java Supported by the language Optimized and easy to test JSON For communicating with the same server JSONP For cross server communication Overgoes the Same Origin Policy Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 15 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 16

5 Remote Procedure Code GWT Remote Procedure Call RPC contains: the service that runs on the server the method you are calling the client code that invokes the service the Java data objects that pass between the client and server Both (client and server) must serialize and deserialize the objects You need to write three components Define the interface StockPriceService that extends RemoteService and lists all your RPC methods Create a class StockPriceServiceImpl that extends RemoteServiceServlet and implements the interface you created above. Define an asynchronous interface StockPriceServiceAsync to your service to be called from the client-side code. Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 17 GWT Remote Procedure Call 1 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 18 StockPriceService interface In the package com.google.gwt.sample.stockwatcher.client import com.google.gwt.user.client.rpc.remoteservice; import com.google.gwt.user.client.rpc. stockprices ) public interface StockPriceService extends RemoteService { StockPrice[] getprices(string[] symbols); 1 Source: code.google.com Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 19 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 20

6 StockPriceServiceImpl class package com.google.gwt.sample.stockwatcher.server; import com.google.gwt.sample.stockwatcher.client.stockprice; import com.google.gwt.sample.stockwatcher.client.stockpriceservice; import com.google.gwt.user.server.rpc.remoteserviceservlet; import java.util.random; public class StockPriceServiceImpl extends RemoteServiceServlet implements StockPriceService { private static final double MAX PRICE = 100.0; // $ private static final double MAX PRICE CHANGE = 0.02; // +/ 2% public StockPrice[] getprices(string[] symbols) { Random rnd = new Random(); StockPrice[] prices = new StockPrice[symbols.length]; for (int i=0; i<symbols.length; i++) { double price = rnd.nextdouble() MAX PRICE; double change = price MAX PRICE CHANGE (rnd.nextdouble() 2f 1f); prices[i] = new StockPrice(symbols[i], price, change); return prices; Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 21 Invoking the service from the client Making asynchronous calls to the server import com.google.gwt.user.client.rpc.asynccallback; public interface StockPriceServiceAsync { void getprices(string[] symbols, AsyncCallback<StockPrice[]> callback); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 23 Include the server-side code in the GWT module Define new servlets in the web.xml <web app> <welcome file list> <welcome file>stockwatcher.html</welcome file> </welcome file list> <servlet> <servlet name>stockpriceserviceimpl</servlet name> <servlet class>com.google.gwt.sample.stockwatcher.server. StockPriceServiceImpl</servlet class> </servlet> <servlet mapping> <servlet name>stockpriceserviceimpl</servlet name> <url pattern>/stockwatcher/stockprices</url pattern> </servlet mapping> </web app> Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 22 Making the remote procedure call private void refreshwatchlist() { // Initialize the service proxy. if (stockpricesvc == null) { stockpricesvc = GWT.create(StockPriceService.class); // Set up the callback object. AsyncCallback<StockPrice[]> callback = new AsyncCallback< StockPrice[]>() { public void onfailure(throwable caught) { // TODO: Do something with errors. public void onsuccess(stockprice[] result) { updatetable(result); ; // Make the call to the stock price service. stockpricesvc.getprices(stocks.toarray(new String[0]), callback); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 24

7 Serializing Java objects GWT RPC requires that all service method parameters and return types be serializable. import java.io.serializable; JSON public class StockPrice implements Serializable { private String symbol; private double price; private double change;... Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 25 Retrieving JSON Data JSON stands for JavaScript Object Notation Language independant format Very light Example [ { symbol : ABC, price : 87.86, change : 0.41, { symbol : DEF, price : 62.79, change : 0.49 ] Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 27 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 26 Server part JSON can be generated by a servlet out.println( { ); out.print( \ symbol\ : \ ); out.print(stocksymbol); out.println( \, ); out.print( \ price\ : ); out.print(price); out.println(, ); out.print( \ change\ : ); out.println(change); out.println(, ); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 28

8 JSON generated by PHP <?php header( Content Type: text/javascript ); define( MAX PRICE, 100.0); // $ define( MAX PRICE CHANGE, 0.02); // +/ 2% echo [ ; $q = trim($ GET[ q ]); if ($q) { $symbols = explode(, $q); for ($i=0; $i<count($symbols); $i++) { $price = lcg value() MAX PRICE; $change = $price MAX PRICE CHANGE (lcg value() ); echo { ; echo \ symbol\ :\ $symbols[$i]\, ; echo \ price\ :$price, ; echo \ change\ :$change ; echo ; if ($i < (count($symbols) 1)) { echo, ; echo ] ;?> Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 29 Manipulate JSON objects Create a JavaScriptObject StockData to manipulate the data input in Java import com.google.gwt.core.client.javascriptobject; class StockData extends JavaScriptObject { // Overlay types always have protected, zero argument constructors. protected StockData() { // JSNI methods to get stock data. public final native String getsymbol() / { return this.symbol; /; public final native double getprice() / { return this.price; /; public final native double getchange() / { return this.change; /; // Non JSNI method to return change percentage. public final double getchangepercent() { return getchange() / getprice(); Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 31 Transform JSON object into JavaScript use the built in JavaScript function eval The function will receive a response.gettext() as a parameter private final native JsArray<StockData> asarrayofstockdata( String json) / { return eval(json); /; Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 30 Connect the Web server Prepare the list of stocks private void refreshwatchlist() { if (stocks.size() == 0) { return; String url = JSON URL; // Append watch list stock symbols to query URL. Iterator iter = stocks.iterator(); while (iter.hasnext()) { url += iter.next(); if (iter.hasnext()) { url += + ; url = URL.encode(url); // TODO Send request to server and handle errors. Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 32

9 Connect the Web Server (Cont.) Conclusion GWT // Send request to server and catch any errors. RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, url); try { Request request = builder.sendrequest(null, new RequestCallback() { public void onerror(request request, Throwable exception) { displayerror( Couldn t retrieve JSON ); public void onresponsereceived(request request, Response response ) { if (200 == response.getstatuscode()) { updatetable(asarrayofstockdata(response.gettext())); else { displayerror( Couldn t retrieve JSON ( + response. getstatustext() + ) ); ); catch (RequestException e) { displayerror( Couldn t retrieve JSON ); Google Web Toolkits One Application = one language Development in JavaScript is made easy Client Server Communication is hidden Security Issues Communication is blured What is tested where? Who does what? Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 33 Conclusion AWT Java on a Server Servlet : for small programms (alternative to PHP) Java Server Faces : For large programms with a huge Middle tier Web Security Very important to test and validate inputs Encode outputs Verify everything Do not allow access to your intern kitchen to attackers Remove error messages GWT Only one language from the client to the server Quality Management Can you please fill out the given questionnaire Purely informative, for my use only Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 34 References Google Code overview.html Tutorial for Client Server communication latest/tutorial/clientserver.html Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 35 Berner Fachhochschule Haute cole spcialise bernoise Berne University of Applied Sciences 36