Talk given at the rivieradev conferences Oct-2011

1. GwtQuery:
A jQuery clone for GWT, and much more ...
Manuel Carrasco Moñino
manolo@apache.org
@dodotis

2. About me
● Apache James
● HUPA
● GWT
● Gquery & Gquery-plugins
● GwtExporter
● GwtUpload
● Chronoscope
● Jenkins
● Performance plugin
● Emma plugin
● Linux
● LXP a light and visual window manager based on icewm

3. Contents
● What is GWT
● What is Gquery
● Learning Gquery
– GQuery, $(), Function
– Collections & grabbing Values
– Selectors
– Traversing the DOM
– Method Chaining
– CSS
– Events
– Effects
– Ajax
– Data binding
– Plugins
● Js Size
● jsQuery

4. What is GWT
Java to Javascript Compiler, Linker, Optimizer and Obfuscator
One compiled 'js' per browser (like c++ one 'exec' per processor)
Is a full SDK. Not a Js Framework
Not a Js Library
Not a new language
Not a Web Framework

5. Advantages of using Java.
● A high level language allows that the developer doesn't get
lost with low level details: DOM, Ajax, Cross-domain,
Compression, Obfuscation, Dependencies, Browser
differences, etc.
● Huge Java ecosystem: IDE, Re-factoring, Debug, Code assist,
Maven.
● Metrics, TDD, CI, Reusing (libraries)
● Patterns, Builders …
● Type safe, syntax checking, reduce errors.
● Separate code maintenance from the effectiveness of the
executable.
● Normally, the compiler would produce better js code than the
code we could write by hand (less code, compressed,
obfuscated, remove dead code, etc).

6. What does the Gwt SDK provide
●
Generators, Compiler, Linker, Optimizer, Obfuscater.
●
Client side libraries: DOM, XML, JSON, RPC, RF, I18n, MVP,
Widgets
●
Server libraries: RPC, RF
●
Eclipse plugin
●
Multi-browser Dev mode
●
Unit testing and Debug tools.
●
Performance tools (speed tracer)
●
Compiler Statistics
●
Everything is open sourced (Apache v2.0)

7. GWT Eclipse
Java Code (IDE) Plugin
Java Server Java Client
Side Side
Toolkit (SDK)
GWT development GWT Compiler
Debug/Hosted/Test JRE Emulation
Browser libs
GWT server Widgets
libs RPC/RF
Test Runner FF/IE/Ch-Plugin
3ª Party 3ª Party
Server libs Client libs
JavaScript. GQuery
J-Byte Code
Bundles (css, sprite).
JSON/XML/HTML/TXT JSON/XML/HTML/TXT
RPC/RF Browser
Any Backend
JVM App-Server
(php, ruby, ...)

8. What is GQuery
● A library for GWT
● Provides jQuery API and syntax (small differences)
● Entirely re-written in java, not a wrapper, optimized for Gwt.
● Has many features not available in jQuery.
– Data binding generators
– Type-safe structures
– Compile selectors
● It is a useful complement for Gwt.
– CSS selectors
– Widget finders
– Light weight collections
– DOM and Widget enhancers.
● Can be used as an alternative to traditional Gwt developing (progressive
enhancement)
● Performance in mind, Unit tested.
● Extensible via Plugins

9. Easy to getting started
●
Use the gquery maven Archetype.
mvn archetype:generate
-DarchetypeGroupId=com.googlecode.gwtquery
-DarchetypeArtifactId=gquery-archetype
-DarchetypeVersion=1.1.2
-DgroupId=fr.rivieradev
-DartifactId=hello
-DprojectName=HelloWorld
●
Maven Ready (see README.txt).
mvn clean package
mvn gwt:run

10. IDE Friendly
● Eclipse, IntelliJ, Netbeans
● Run, Debug, Test
● Code Assist
● Re-Factoring
● Software Metrics

11. The GQuery Object
● Like in jQuery ...
● Selectors return an object ...
● Which represents a collection of Elements ...
● And each has plenty of useful methods.
● Most methods return the object itself so you can chain
them.
● Other methods return a value of the first element
GQuery g = $("img.photo");
g.attr("src", "/default.png");
String color = g.css("color");
int size = $("img.photo").css("border", "none").size();

12. The Dollar '$()' Method
● As in Javascript, the symbol '$' is legal for methods and
classes.
● But The Gwt Compiler disallows it for class names, So we use
GQuery.
// Import GQuery utility methods statically
// it should be ...client.$.* but the compiler complains
import static com.google.gwt.query.client.GQuery.*;
// The '$' method always returns a GQuery object
GQuery g;
// Use '$' to create new DOM elements
g = $("<div>hello</div>");
// Use '$' to select DOM elements
g = $("div:hidden");
// Use '$' to wrap existing elements
g = $(document);
// Use '$' to wrap Gwt widgets
Button button = new Button();
g = $(button);
// '$' can handle other arguments:
// Function, Event, Element[], NodeList ...

13. Functions
●
java hasn't got closures.
●
We use 'Function' inner class to emulate javascript function
●
Override the appropriate 'f()' to write your code

14. Collections and Grabbing Values
GQuery Java. jQuery JavaScript.
// Returns a GQuery object // Returns a jQuery object
GQuery g = $("div.section"); var g = $('div.section');
// Returns a nodelist // Returns a nodelist
NodeList<Element> l = $("div.section").get(); var l = $('div.section').get();
// Returns the size of the collection // Returns the size of the collection
int size = $("div.section").size(); var size = $('div.section').size();
// Modify all elements in the collection // Modify all elements in the collection
$("div.section").addClass("highlighted"); $('div.section').addClass('highlighted');
$("a.foo").html("<em>Hello</em>"); $('a.foo').html('<em>Hello</em>');
// Iterate and runs a function around each // Iterate and runs a function around each
// element // element
$("div.section").each(new Function(){ $('div.section').each(function(){
public void f() { $(this).css('background', 'red');
$(this).css("background", "red"); });
}
});
// Some methods return results from the first // Some methods return results from the first
// matched element // matched element
int height = $("div#intro").height(); var height = $("div#intro").height();
String src = $("img.photo").attr("src"); var src = $("img.photo").attr('src');
String lastP = $("p:last").html(); var lastP = $("p:last").html();
- We have to define the appropriate return type.
- and to use double instead of single quotes

15. Selectors
● Both GQuery and jQuery are built around selectors.
● Both support CSS standard selectors plus extra selectors
(:text :password :hidden etc).
● jQuery uses the sizzle engine. A javascript engine which works
with any browser and has optimizations per browser.
● GQuery has optimized engines written in java.
● The more appropriate engine is selected in compile time.
● GQuery uses a modified sizzle version for IE6/7
● GQuery adds compile-time optimizations when using compiled
selectors.

16. Dynamic selectors
$("#note");
●
Use $(string) with dynamic selectors
$(".note");
$("body");
$("div p");
●
Add the context if the target
$("div + p");
$("div .example");
elements have not been attached yet
$("div > div");
$("div ~ p");
or to improve performance.
$("h1[id]:contains(Selectors)");
$("tr:first");
$("tr:last");
●
It supports XML documents as well
$("*:checked");
$("*:visible");
$("a[href][lang][class]");
$("div:not(.example)");
$("div[class]");
$("div[class*=e]"); String className = "note";
$("div[class=example]"); $("." + className);
$("div[class~=dialog]");
$("div[class^=exa]"); // Specify the context to improve performance
$("div[class$=mple]"); Element e = DOM.getElementById("whatever");
$("p:first-child"); $(".note", e);
$("p:last-child");
$("p:nth-child(n)"); // Use the context with unattached elements
$("p:nth-child(2n)"); Widget w = new MyWidget();
$("p:nth-child(2n+1)");
$(".note", w);
$("p:nth-child(even)");
$("p:nth-child(odd)");
$("p:only-child");
[...]

17. Compiled Selectors
●
Use them with immutable selectors.
●
And when selector performance is a
goal in your application.
●
Context is supported
interface MySelectors extends Selectors {
@Selector("*:checked")
GQuery allChecked();
@Selector("*:checked")
GQuery allChecked(Node context);
}
public void onModuleLoad() {
MySelectors selectors = GWT.create(MySelectors.class);
selectors.allChecked();
Element e = DOM.getElementById("whatever");
selectors.allChecked(e);
}

18. Selectors Performance
→ Click to open the benchmarking application

19. Selectors Performance
●
GQuery in compiled mode produces the faster javascript code to select
DOM elements.
●
GQuery dynamic selectors are, in most cases, faster or equal than any
other library.

20. Traversing the Dom
●
Like jQuery, GQuery provides enhanced methods for
traversing the DOM
GQuery nextSibling = $("div.section").next();
GQuery prevSibling = $("div.section").prev();
GQuery prevAnchorSibling = $("div.section").prev("a");
GQuery firstParent = $("div.section").parent();
GQuery allParents = $("div.section").parents();
●
Additionally it provides useful method to locate Gwt
Widgets.
// We can traverse the DOM to locate widgets
// Return the CellTree widget whose id is myTree
CellTree tree = $("#myTree").widget();
// Now we can use the instance
tree.addCloseHandler(...);
// Return all gwt Labels in the dom
List<Label> allLabels = $("div").widgets(Label.class);

21. Chaining Methods
●
Most GQuery methods return another GQuery object often
representing the same collection. This means that you can
chain methods together.
$("div.section").show().addClass("comeBack");
●
Crazy chaining.
$("form#login")
// hide all the labels inside the form with the "optional" class
.find("label.optional").hide().end()
// add a red border to any password fields in the form
.find("input:password").css("border", "1px solid red").end()
// add a submit handler to the form
.submit(new Function(){
public boolean f(Event e) {
return confirm("Are you sure you want to submit?");
}
});

22. CSS
// jQuery like syntax: property, value
$("#myId")
.css("color", "red");
// jQuery like syntax: javascript object
$("#myId")
.css($$("top: '50px', left: '25px', color: 'red'"));
// Additionally GQuery supports css style-sheet syntax (copy and paste)
$("#myId")
.css($$("margin: 3px; padding: 3px; font-size: small;"));
// Many properties require a strict syntax:
// background: color url repeat attachment position
$("#myId").css("background", "transparent url('back.jpg') no-repeat scroll center");
// border: width style color
$("#myId").css("border", "medium dotted #cdcd");
- We use the '$$' method to generate javascript property structures

23. CSS Type-safe
// Set the border style of a button widget to 'dotted' value
Button myButton = new Button();
$(myButton).css(CSS.BORDER_STYLE.with(BorderStyle.DOTTED));
// vertical-align can take a constant value
$("#myId").css(CSS.VERTICAL_ALIGN.with(VerticalAlign.MIDDLE));
// or a length : here 120 px
$("#myId").css(CSS.VERTICAL_ALIGN.with(Length.px(120)));
// it easy now to specify shorthand property,
// we do not have to remember the order!
$("#myId").css(CSS.BACKGROUND.with(
RGBColor.TRANSPARENT,
UriValue.url("back.jpg"),
BackgroundRepeat.NO_REPEAT,
BackgroundAttachment.SCROLL,
BackgroundPosition.CENTER));
// specify margin, padding, text-decoration and font-size in one pass
$("#myId").css(CSS.MARGIN.with(Length.px(3)),
CSS.PADDING.with(Length.px(3), Length.px(5)),
CSS.TEXT_DECORATION.with(TextDecoration.NONE),
CSS.FONT_SIZE.with(FontSize.SMALL));

24. Events
●
GQuery provides methods for assigning
event in a cross-browser way.
●
GQuery event system is compatible with
Gwt.
●
issues:
– When Gwt detaches a widget, events added via
GQuery are lost.
– If you use 'live' for future elements, consider
performance (be carefully with 'onmouse...' events)

25. Events examples
// GQuery provides methods for assigning event
// handlers to elements in a cross-browser way.
$("a").click(new Function() {
public boolean f(Event ev) {
$(this).css("backgroundColor", "orange");
// return false to stop default action and event-bubbling
return false;
}
});
// Fires the event click on all labels
$(".gwt-Label").click();
// Remove event handlers
$("a").unbind("click");
// Attach a handler to all elements matching the
// selector, now and in the future
$("a")
.live("over", new Function(){
public void f() {
$(this).css("color", "red");
}
})
// Type-safe
.live(Event.ONMOUSEOUT, new Function(){
public void f() {
$(this).css("color", null);
}
});

26. Effects
●
GQuery provides several techniques for adding animations to a web
page.
●
These include simple, standard animations that are frequently used:
●
fadeIn, fadeOut, slideDown, slideUp …
$(".foo").fadeIn(2000);
●
and the ability to craft sophisticated custom effects via the animate
method using jquery animation syntax
●
queue, delay, stop, css, attr, colors ...
$(".foo")
.stop()
.animate("left:'+=1000'", 2000, Easing.SWING)
.delay(500)
.animate("left:'-=1000'", 2000);
→ Go to zoom example

27. Ajax
●
Gwt includes its own facilities for
performing communications with the
server:
●
RPC, Request Factory (Only Java)
●
Request Builder
●
But GQuery complements it adding:
●
jQuery syntax.
●
Builders to handle JSON and XML.

28. Ajax methods
GQuery Java. jQuery JavaScript.
// Load a remote html fragment in a set of // Load a remote html fragment in a set of
// dom elements // dom elements
$("#c").load("file.html #mid"); $('#c').load('file.html #mid');
// Unsupported in GQuery
// More advanced methods $.getScript(url, callback);
GQuery.get("file.html", null, new Function(){
public void f() { // More advanced methods
alert("success " + getData()[0]); $.get('file.php', null, function(data){
} alert("success " + data);
}); });
GQuery.post("file.html",$$("name:'John',time:'2pm'"), $.post('file.php', {name: 'John', time: '2pm'},
new Function(){ public void f() { function(data){
alert("success " + getData()[0]); alert("success" + data);
}}); });
GQuery.getJSON("file.html",$$("name:'John',time:'2pm'"), $.getJSON('file.php', {name: 'John', time: '2pm'},
new Function(){ public void f() { function(data){
alert("success " + getData()[0]); alert("success" + data);
}}); });
- Gwt compiler disallows a class named '$', so we use 'GQuery'

29. Data binding
● Although Gquery
– provides the class 'Properties' to handle Json objects...
Properties p = $$("key1: 'value1', key2: [1,2]");
String v1 = p.getStr("key1");
– and it is able to inspect Xml objects using css selector engine...
Element e = JsUtils.parseXML("<root><message>hello</message></root>");
String txt = $("root message", e).text();
GQuery provides generators to produce builders and handle Xml and
Json as 'java' objects.
● Data binding objects support getters, setters and attribute
renaming via annotations
● The usage of data binding makes the code more readable, type-
safe, checks null conditions, castings, etc.

30. Data binding example
// GQuery generator will create the implementation
interface Site extends JsonBuilder {
long getId();
String getUrl();
String[] getTags();
// change the name to fix the misspelling
@Name("referer") Site getReferrer();
String getTitle(); [{
"id": 1234,
"referer": {"id": 2, "url": "http://google.com"},
//NOTE: Setters not displayed to simplify "url": "http://mochikit.com/interpreter/index.html",
} "title": "Interpreter",
"tags": [
GQuery.getJSON("test.json", null, new Function() { "mochikit","webdev","tool","tools",
public void f() { "javascript","interactive","interpreter","repl"
// Create the Site instance ]
Site s = GWT.create(Site.class); }]
// Load the data got from the server
s.load(getData()[0]);
// We can use standard getters and setters,
// making the code more readable and type-safe
alert("OK " +
s.getUrl() + " " +
s.getTags()[0] + " " +
s.getReferrer().getUrl());
}
}); // Alternative: handle data using GQuery Properties class
Properties p = (Properties)getData()[0];
alert ("OK " +
p.getStr("url") + " " +
p.getArray("tags").getString(0) + " " +
((Properties)p.getJavaScriptObject("referer")).getStr("url"));

31. Plugins
●
GQuery is extensible through plugins, adding new features for different
purposes.
●
Because of java constrains, we can not add new methods to the GQuery class
so we have to use the method 'as' to use plugin methods.
●
Core already includes: Events, Effects, Widgets and Ajax plugins
●
GQuery has its own site to host plugins. Contributions welcomed!
→ Go to the plugins site

32. Plugins: Create and Usage
Usage a Plugin.
// jQuery syntax
$("h1").as(MyPlugin).newMethod(); $("h1").newMethod();
Develop a Plugin.
public static class MyPlugin extends GQuery {
// Register the plugin in the GQuery plugin system
public static final Class<MyPlugin> MyPlugin =
Gquery.registerPlugin(MyPlugin.class, new Plugin<MyPlugin>() {
public MyPlugin init(GQuery gq) {
return new MyPlugin(gq);
}
});
// Initialization
protected MyPlugin(GQuery gq) {
super(gq);
}
// Add a new methods to GQuery objects
public GQuery newMethod() {
// Write your code here
return this;
}
}

33. Progressive Enhancement
●
Enhance pure Html pages: Crawlers friendly.
$("a").click(new Function() {
public void f() {
GWT.log("Clicked: " + $(this).text() + " " + $(this).attr("href"));
}
});
●
Enhance Gwt Widgets: Without manipulating the class.
$(".gwt-Button").prepend("<img src='help.png'>");
●
Enhance Gwt Views: MVP pattern compatible.
$("textarea").as(Enhance).richText();

34. JavaScript size
●
Gquery takes advantage of the gwt compiler which produces
optimized and striped code.
●
Gquery core tends to use light-weight stuff to reduce the javascript
size and improve the performance.
●
A small GQuery application normally is smaller than the jQuery
minimized library.
●
The js size which GQuery adds to a Gwt application is 3 or more times
smaller than the jquery library.

35. Comparing sizes
●
The ImageZoom Example needs a 17% less of javascript code (FF).
●
When using deflate-gzip in webserver, gwt js code is pre-ordered
so the compression factor is better.

36. jsQuery
● The latest work in GQuery is to produce a clone of jquery which could
be used as a replacement of jQuery. We call this library jsQuery.
● The goal is not to compete against jquery, but
● To avoid including jquery in Gwt applications which need some native jQuery
methods like jquery plugins.
● As an investigative work which demonstrates that any js API can be
developed in Gwt (jQuery is the js API most widely used).
● We use the gwt-exporter library which is able to expose Gwt classes
and methods to javascript.
● Right now most GQuery object methods are exposed but we have to
implement and export many static methods which are in jQuery like
extend, each, map …
● The main goal is to encourage people to wrap jQuery plugins, just
including them as jsni and creating java wrappers methods around it.

37. jsQuery issues
●
Gwt-exporter introduces a high amount of extra code to deal with types and
wrappers. If we consider compression, jsQuery is only 8KB greater
●
Gwt-exporter spends time figuring out which methods to call and how to wrap
parameters and return objects.
●
Apart of the code in GQuery, we will need extra code to emulate all jQuery
API.

38. jsQuery example
<!-- <script src="http://code.jquery.com/jquery-latest.min.js" /> -->
<script src="http://code.google.com/p/gwtquery/source/browse/api/jsquery.nocache.js" />
<script type="text/javascript">
$(document).ready(function(){
$("ul.thumb li").hover(function() {
$(this).css({'z-index' : '10'});
$(this).find('img').addClass("hover").stop()
.animate({
marginTop: '-110px',
marginLeft: '-110px',
top: '50%',
left: '50%',
width: '174px',
height: '174px',
padding: '20px'
}, 200);
} , function() {
$(this).css({'z-index' : '0'});
$(this).find('img').removeClass("hover").stop()
.animate({
marginTop: '0',
marginLeft: '0',
top: '0',
left: '0',
width: '100px',
height: '100px',
padding: '5px'
}, 400);
});
});
</script>

39. Links
GwtQuery
http://code.google.com/p/gwtquery/
http://gwtquery.googlecode.com/svn/trunk/gwtquery-core/javadoc/com/google/gwt/query/client/GQuery.html
http://code.google.com/p/gwtquery/w/list
http://code.google.com/p/gwtquery-plugins/
Plugins
http://gwtquery-plugins.googlecode.com/svn/trunk/ratings/demos/Ratings/RatingsSample.html
http://gwtquery-plugins.googlecode.com/svn/trunk/enhance/demos/Enhance/EnhanceSample.html
http://gwtquery-plugins.googlecode.com/svn/trunk/droppable/demo/GFinderSample/GFinderSample.html
http://gwtquery-plugins.googlecode.com/svn/trunk/droppable/demo/GwtPortletSample/GwtPortletSample.html
http://gwtquery-ui.googlecode.com/svn/demos/GwtQueryUi.html
Application
http://talkwheel.com

40. Conclusions
● People knowing jquery can easily use GQuery because share the API.
● GQuery uses java :
– Type safe, discover errors early (compile time instead of runtime)
– Advanced IDE (code completion, refactoring)
– Most people knows java but only a few js.
● GQuery uses gwt:
– Do not worry about compression, obfuscation …
– TDD, Debug
– Many libraries available
● GQuery complements the Gwt world making easier code: write less, do more.
● GQuery helps to develop applications using the jquery paradigm based on
Enhancement, instead of the Gwt one based on Widgets.
● GQuery is mature, just released version 1.1.0, and well documented.
● The GQuery plugin system is simple.
● Contributors are Welcome !!!

41. Announcement
GQuery 1.1.0 released today !
We wanted to match the new release announcement
with the RivieraDev event.