GWT In-depth

Explained by Rohit Ghatol(rohitsghatol@gmail.com)

http://pune-gtug.blogspot.com

Topics Covered

• Short Introduction to GWT• Architectural Overview• Simple Code Example• MVC Code Example• Server Communication using GWT – RPC• Open source Libraries

Introduction to GWT

Read more on GWT Overview Page

Key Features

Read more on GWT Overview Page

Key Features

Read more on GWT Overview Page

GWT Documentation Links

• Developer's Guide– Fundamentals – User Interfaces – Remote Procedure Calls – Unit Testing – Internationalization – JavaScript Native Interface (JSNI) – JRE Emulation – GWT Class API

Install GWT

E:\Work\GWT-Demo>set PATH=e:\worksoft\gwt-windows-1.4.60;%PATH%

E:\Work\GWT-Demo>projectCreator -eclipse SimpleDemoCreated directory E:\Work\GWT-Demo\srcCreated directory E:\Work\GWT-Demo\testCreated file E:\Work\GWT-Demo\.projectCreated file E:\Work\GWT-Demo\.classpath

E:\Work\GWT-Demo>applicationCreator -eclipse SimpleDemo com.gwt.demo.client.SimpleDemoCreated directory E:\Work\GWT-Demo\src\com\gwt\demoCreated directory E:\Work\GWT-Demo\src\com\gwt\demo\clientCreated directory E:\Work\GWT-Demo\src\com\gwt\demo\publicCreated file E:\Work\GWT-Demo\src\com\gwt\demo\SimpleDemo.gwt.xmlCreated file E:\Work\GWT-Demo\src\com\gwt\demo\public\SimpleDemo.htmlCreated file E:\Work\GWT-Demo\src\com\gwt\demo\client\SimpleDemo.javaCreated file E:\Work\GWT-Demo\SimpleDemo.launchCreated file E:\Work\GWT-Demo\SimpleDemo-shell.cmdCreated file E:\Work\GWT-Demo\SimpleDemo-compile.cmd

Demo GWT Project

• Site - http://code.google.com/p/gwt-simple-demo/• Download demo project from here

GWT Project Anatomy

GWT-Demo +src +com/gwt/demo SimpleDemo.gwt.xml - client SimpleDemo.java - public SimpleDemo.html

GWT Project Anatomy

SimpleDemo.gwt.xml

1. Module XML Definition File 2. Includes Project Dependencies3. Includes Entry Point4. Includes RPC Servlet Entry

SimpleDemo.java

1. This is the Entry Point2. Entry Point is like Main Method3. Widgets are added to RootPanel

SimpleDemo.html

1. This is the final deliverable HTML/JSP/ASP/PHP 2. Includes JS file for SimpleDemo3. Includes PlaceHolder Elements

Shuffle Box Example

Shuffle Box ExampleRootPanel

Shuffle Box Example

HorizontalPanel

Shuffle Box Example

VerticalPanel

Shuffle Box Example

Shuffle Box Example

Shuffle Box Examplenew ClickListener(){ public void onClick(Widget sender) { int leftIndex=leftListBox.getSelectedIndex(); if(leftIndex==-1){ Window.alert("Select an Item from Left List Box"); } else{ String item=leftListBox.getItemText(leftIndex); leftListBox.removeItem(leftIndex); rightListBox.addItem(item); } }}

Observable

# List observers+ addObserver(Observer observer)+ removeObserver(Observer observer)+ notifyObservers()

Observer<<Interface>>

+ update(Observable model)

Notify

Register/Unregister

View Source for Observable.java View Source for Observer.java

MVC Demo

MVC Demo

MVC Demo

# temperature+ setTemp(int temp)+int getTemp()

TempModel

# observers+ addObserver()+removeObserver()+ notifyObserver()

Observerable

FahrView CelsView ThermoView

update(Observable mode)

Observer

MVC Demo

# temperature+ setTemp(int temp)+int getTemp()

TempModel

# observers+ addObserver()+removeObserver()+ notifyObserver()

Observerable

FahrView CelsView ThermoView

update(Observable mode)

Observer

Renders

MVC Demo

# temperature+ setTemp(int temp)+int getTemp()

TempModel

# observers+ addObserver()+removeObserver()+ notifyObserver()

Observerable

FahrView CelsView ThermoView

update(Observable mode)

Observer

Register

MVC Demo

# temperature+ setTemp(int temp)+int getTemp()

TempModel

# observers+ addObserver()+removeObserver()+ notifyObserver()

Observerable

FahrView CelsView ThermoView

update(Observable mode)

Observer

User clicked increment button

Changes

MVC Demo

# temperature+ setTemp(int temp)+int getTemp()

TempModel

# observers+ addObserver()+removeObserver()+ notifyObserver()

Observerable

FahrView CelsView ThermoView

update(Observable mode)

Observer

Notifies

All the Views Update themselves using update() method

MVC Demo source files

• FahrView.java• CelsView.java• ThermoView.java• TempModel.java

RPC Demo

RPC Demo

RPC Demo

RPC Classes Explained

LocationService<<Interface>>

List getStates(String country)

LocationServiceImpl

List getStates(String country)

RemoteService<<Interface>>

List getStates(String country)

RemoteServiceServlet

LocationServiceAsync<<Interface>>

Void getStates(String country, AsyncCallback callback)

LocationServiceUtil

public static LocationServiceAsync getInstance()

GWT

MagicGlue

GWT Classes

RPC Classes Explained

AsyncCallback<<Interface>>

void onSuccess(Object result);

void onFailure(Throwable caught);

LocationServiceUtil Code

• Use GWT Glue to link LocationService and LocationServiceAsync classes

LocationServiceAsync serviceAsync = (LocationServiceAsync) GWT .create(LocationService.class);

• Set the Service’s Entry point (aka url)

((ServiceDefTarget) serviceAsync).setServiceEntryPoint(GWT.getModuleBaseURL()+ "/LocationService");

LocationServiceUtil Code

public class LocationServiceUtil { public static LocationServiceAsync createService() { LocationServiceAsync serviceAsync = (LocationServiceAsync) GWT .create(LocationService.class);

((ServiceDefTarget) serviceAsync).setServiceEntryPoint(GWT.getModuleBaseURL()+ "/LocationService"); return serviceAsync; }}

RPC Client Code

LocationServiceAsync serviceAsync = LocationServiceUtil.createService();serviceAsync.getStates(country, new AsyncCallback() {

public void onFailure(Throwable caught) {Window.alert("System Error!");

}

public void onSuccess(Object result) {List list = (List) result;statesListBoxModel.setEntries(list);

}});

RPC related Links

• Complete source code• LocationService.java• LocationServiceAsync.java• LocationServiceImpl.java• LocationServiceUtil.java• Client Code• RPC Tutorial

Extending Widgets for more events

onBrowserEvent(Event event)

Widget

FocusWidget

ListBox

Extending Widgets for more events

• Some Facts about ListBox widget– Following Listeners can be added• Change• Focus• Keyboard

– Extends FocusWidget which extends Widget– ListBox does not receive a DoubleClick event as it

never sinks it.

Extending Widgets for more events

• Some Facts about Widget class– A Widget needs to sink events in its constructor to

receive it– Widget class has an important method• void onBrowserEvent(Event event) which handles all

the events (eventually)

Extending Widgets for more events

• Some Facts about Widget class– If a Widget needs to receive a DoubleClick event it

needs to call sinkEvents(Event.ONDBLCLICK)

– If a Widget needs to handle this new DoubleClick event it needs to override onBrowserEvent method and handle this event

Extending Widgets for more events

# dblClickListenerCollection+ AdvListBox()# onBrowserEvent(Event event)

AdvListBox

ListBox

addDblClickListener()removeDblClickListener()fireDblClickEvent(Widget sender)

DblClickListenerCollection

ArrayList

Void onDoubleClick(Widget sender)

DblClickListener<<Interface>>

0..*

1

Extending Widgets for more events

public class AdvListBox extends ListBox { private DoubleClickListenerCollection dblClickListeners = new DoubleClickListenerCollection();

public AdvListBox() { this.sinkEvents(Event.ONDBLCLICK); }

public void onBrowserEvent(Event event) { super.onBrowserEvent(event); if(DOM.eventGetType(event)==Event.ONDBLCLICK){ dblClickListeners.fireDoubleClickEvent(this); } }

public void add(DoubleClickListener listener) { dblClickListeners.add(listener); }

public void remove(DoubleClickListener listener) { dblClickListeners.remove(listener); }}

AdvListBox.java Source

Extending Widgets for more eventsSource files• AdvListBox.java • AdvListBoxDemo.java • DoubleClickListener.java • DoubleClickListenerCollection.java

Open Source GWT Libraries Demos

• MyGWT – Many Rich UI widgets• GWT-DND – Meant for drag and drop

MyGWT

GWT-DND