- Polymer: is a JavaScript library for building web applications with Web Components.
- Polymer-Elements: is a collection of widgets built in Polymer. The collection is divided in sections: Iron, Paper, Gold, Neon, Platinum, Vaadin, etc.
- GWT-Polymer-Elements: is a Java wrapper enabling Polymer Elements to be used in GWT projects. Right now it includes wrappers for Iron, Paper, App, Platinum and Vaadin collections, but more might be added in the future.
The library has been generated using the Vaadin gwt-api-generator, an utility able to inspect polymer webcomponents and emit GWT Java code.
Because Polymer differentiates between collections, gwt-polymer-elements classes are prefixed with the same prefixes (Iron, Paper, Vaadin), in order to easily refer to the original web component, and to easily find the documentation related with it.
Visit our show case to see how components look like, and to take a look to the example code using each component.
When we parse the original components code to generate the Java API, we copy all the existing JS documentation so as it's available in the javadoc. Note that sometimes descriptions would refer to JS, but we consider that it's better to maintain the info.
NOTICE : We make an extensive use of JsInterop
, a new feature in GWT
for easily interacting with JavaScript.
It was experimental in GWT-2.7
, and stable in GWT-2.8.0
, but starting from gwt-polymer-elements-1.2.1.0.beta1, we don't support 2.7.0 anymore or it's legacy JsInterop syntax.
The .jar
file includes all the java code and web components of
Polymer Iron and Paper collections, so as you don't have to deal with the process of downloading and deploying all js wrapped libraries and components.
- If your project uses maven add the dependency:
<dependencies>
<dependency>
<groupId>com.vaadin.polymer</groupId>
<artifactId>vaadin-gwt-polymer-elements</artifactId>
<version>1.7.0.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
- otherwise you can download
the
vaadin-gwt-polymer-elements-1.7.0.0.jar
archive and put it in your gwt project classpath.
- Add this line to your
*.gwt.xml
module file:
<inherits name="com.vaadin.polymer.Elements"/>
### Add the Web Components Polyfill (Optional).
-
Only Chrome has full native support for Web Components nowadays, therefore, to make your project work with all modern browsers, you have to include the WebComponents Polyfill.
If you use the polymer components as
Widgets
, the library will lazy load it when needed. Otherwise load it very early in your.html
host page as it is shown in the following code.
Vaadin gwt-polymer-elements
bundles classes to build your application using either Widgets
or JsInterop Elements
. The former is the classic approach, while the latter will become the new tendency.
But Right now, Elements
is the most difficult way because GWT lacks of a complete Elemental-2.0
API relying on JsInterop
.
We provide a very small set of elemental interfaces limited to those needed for our implementation, they will be replaced by Elemental-2.0 when it was available.
In summary, for classic and production GWT projects it would be easier to use the Widget
since the API would not have important changes. Otherwise, if you want to get rid of the widget hierarchy we recommend to start using the Element
API mixing it with some DOM manipulation library like gwtquery
or just the methods included in the elemental API.
- Using the classic Widget API in Java.
PaperButton button = new PaperButton();
button.setIcon("polymer");
button.setLabel("Polymer");
button.setRaised(true);
button.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
// ...
}
});
RootPanel.get().add(button);
Note: Widget constructors accept any HTML content as argument which is appended to the web component rendered DOM
- Using the Element API in Java.
// Create a new instance of PaperButton
PaperButtonElement button = Polymer.create(PaperButtonElement.TAG);
// Set some properties
button.setIcon("polymer");
button.setLabel("Polymer");
button.setRaised(true);
// Add event listeners
button.addEventListener("click", new EventListener() {
public void onBrowserEvent(Event event) {
// ...
}
});
// Append to the html document
RootPanel.get().getElement().appendChild(button);
- Using
Widgets
orElements
in UiBinder
<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
xmlns:g='urn:import:com.google.gwt.user.client.ui'
xmlns:p='urn:import:com.vaadin.polymer.paper.widget'>
<ui:style>
.container paper-button.colored {
background: #4285f4;
color: #fff;
}
</ui:style>
<g:HTMLPanel>
<!-- As Widget -->
<p:PaperButton toggles="true" raised="true" active="true" addStyleNames="{style.colored}">active</p:PaperButton>
<!-- As Element -->
<paper-button raised="" noink="">Click me</paper-button>
</g:HTMLPanel>
Polymer uses Shadow DOM styling rules for providing scoped styling of the element’s local DOM. It supports some extra syntax which is not understable by the GWT GSS parser.
Polymer takes care of its syntax parsing any <style>
block you might have in your host page, but if you want to specify some styling rules in UiBinder, you have to add your style blocks to any panel.
<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
xmlns:g='urn:import:com.google.gwt.user.client.ui'
xmlns:p='urn:import:com.vaadin.polymer.paper.widget'>
<g:HTMLPanel>
<style is="custom-style">
paper-toolbar paper-icon-button {
--paper-icon-button-ink-color: var(--paper-indigo-500);
}
</style>
<p:PaperToolbar>
<p:PaperIconButton icon="menu"/>
<span class="title">Toolbar</span>
</p:PaperToolbar>
</g:HTMLPanel>
For more information about polymer styling syntax visit their documentation
Before using any component, you have to import the appropriate files. But gwt-polymer-elements
comes with some utilities so as you it would be done automatically.
- Widgets : When you use a widget, the import happens automatically
PaperButton button = new PapperButton();
- Elements :
Create new components through the
Polymer
helper class
PaperButtonElement button = Polymer.create(PaperButtonElement.TAG);
- Dynamic imports :
Polymer
has a couple of methods to do the import dynamically
Polymer.importHref("paper-button/paper-button.html");
- Static imports : Adding tags to the hosted page head is the traditional way to make webcomponents available if you want them in a mixed application (DOM, JS, or GWT) or if you want to be sure that web components are available from the beginning.
<link rel='import' href='application_context/bower_components/paper-button/paper-button.html'></link>
Polymer 1.x.x does not allow using custom properties before the web component has been initialized.
Thus gwt-polymer-elements
comes with some methods which helps to run callbacks when the component starts ready.
If you use widgets, the library would be able to deal with properties set very early, but call to some methods could not work
PaperButtonElement button = Polymer.createElement(PaperButtonElement.TAG);
Polymer.ready(button, new Function() {
public Object call(Object args) {
// Set button properties here
}
})
PolymerButton button = new PolymerButton();
// You could set methods here
button.setFoo(bar);
button.ready(new Function() {
public Object call(Object args) {
// But you have to enclose in a callback calls to element methods
}
});
Polymer.importHref(Arrays.asList("paper-tabs", "paper-tab-element"), new Function() {
public Object call(Object args) {
// Create your elements here and call their methods
}
})
To compile the vaadin-gwt-polymer-elements
library by yourself.
- Clone the repository with
$ git checkout https://github.com/vaadin/gwt-polymer-elements.git
- Change to the project folder
$ cd gwt-polymer-elements
- Run
$ npm install
to download all components to thesrc/main/resources
folder, to create all java files needed for GWT in thesrc/main/java/
folder and to compile and install the components library in you local maven repo.
- To run and debug the demo, go to the demo folder
$ cd demo
- Run
$ mvn gwt:devmode
to run the demo in SuperDevMode, otherwise run$ mvn clean package
to build the demo application undertarget
directory. - Host the demo either: by running for example
$ serve target/gwt-polymer-demo
(requires serve) or deploying the generatedtarget/gwt-polymer-demo.war
to your favourite servlet container.