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Modularized JavaScript with JBoss Portal Platform 6 – Avoid Conflicts, Promote Re-usability

JBoss Portal Platform 6

JBoss Portal Platform 6 Beta is now available.
http://www.redhat.com/promo/jpp6/

Many new features are documented there:

  • Built on blazingly fast, lightweight JBoss Enterprise Application Platform 6 technology
  • Develop with JSF2 and Rich Faces 4 in portlets, via Portlet Bridge
  • Implement single sign-on (SSO) using SAML 2.0
  • Launch fast with Maven quick starts

Portlet and JavaScript

However, to developers and architects, one of the first issues and most difficult issue we face in any portal implementation is – what are the best practices to use JavaScripts in a portal platform?

Imagine if you have 2 portlets both using a shared JavaScript, such as jQuery – how would you share the JavaScript between the 2 portlets?

  • Each Portlet include its own
    • This is largely a no-no.  If each portlet include its own jQuery in a <script> tag, they’ll most likely run into conflicts or unnecessarily reload a script already loaded.
  • Deploy a single version
    • Then what if you need multiple versions?
    • What if some portlets needs a different version of the JavaScript library?

Now, expand this dilemma to not just common JavaScripts libraries, but to all of your application’s JavaScripts!

Oh, and don’t forget, you may also want to minify and combine scripts to reduce latency, to be Content Delivery Network (CDN) friendly, and ultimately, to improve your customer’s browsing  experience.

How JBoss Portal Platform 6 Helps

JBoss Portal Platform 6 has an exciting new feature to deal with the age old question of how to best deal with JavaScripts in Portlets.

  • JavaScript should be modular and re-usable
  • Dependency management – if a JavaScript depends on another JavaScript, it should load it automatically
  • Each portlet should be able to specify what JavaScript it needs to use
  • If the Portal Platform already provides certain JavaScript libraries, your portlet should still be able to use other versions.  Multiple versions should not cause issues.
  • Work with JavaScripts you already have

All of the above can be accomplished with JBoss Portal Platform 6!  Best of all, it can be achieved using XML-based configurations as well as using JavaScripts to load JavaScript modules.

JavaScript Modules

JBoss Portal Platform 6 fully embraces the concept of JavaScript modules.  For example, you can define a module named “jquery-1.9.0″ to be associated with jquery-1.9.0.js.

Each module definition contains a name, and JavaScript multiple JavaScript files.  For example:

<module>
    <name>jquery-1.9.0</name>
    <script>/javascript/jquery-1.9.0.js</script>
</module>

Note that, JBoss Portal Platform 6 already ships with a module named “jquery” that provides jQuery 1.7.1.  But it’s OK to define another module using a different name.

Dependencies

A JavaScript module can have dependencies to another JavaScript module.  For example, if your application JavaScript “version.js” depends on jQuery:

(function($) {
    alert($().jquery); // Display jQuery version in an alert window.
})($);

First, we can associate the JavaScript with the portlet, so that JBoss Portal Platform 6 can load “version.js” only if the portlet is also on the page, and then specify the dependency:

<portlet>
    <name>jquery-version</name>
    <module>
        <script>
            <path>/javascript/version.js</path>
        </script>
        <depends>
            <module>jquery</module>
        </depends>
    </module>
</portlet>

* JBoss Portal Platform 6 provides jQuery 1.7.1 as a module.  It can be referenced and re-used by any portlet.

You can, of course, specify multiple dependencies.

Multiple Versions?  No Problem!

What if your portlet needs newest jQuery 1.9.0, even though JBoss Portal Platform already has jQuery 1.7.1?  Not to worry – it’s as easy as changing out the dependency!

<portlet>
    <name>jquery-version</name>
    <module>
        <script>
            <path>/javascript/version.js</path>
        </script>
        <depends>
            <module>jquery-1.9.0</module>
        </depends>
    </module>
</portlet>

In fact, you can even use both versions at the same time.

<portlet>
    <name>jquery-version</name>
    <module>
        <script>
            <path>/javascript/version-both.js</path>
        </script>
        <depends>
            <module>jquery</module>
            <as>jq17</as>
        </depends>
        <depends>
            <module>jquery-1.9.0</module>
            <as>jq19</as>
        </depends>
    </module>
</portlet>

The “<as/>” tag will create an alias for the JavaScript so that it can be referred to by the consuming script.  In the above example, out-of-the-box jQuery is now aliased as “jq17″, and our own version is aliased as “jq19″.  These will then be accessible by the consuming script as variables with those names.

And for “version-both.js”:

(function(jq17, jq19) {
    alert(jq17().jquery); // Display jQuery version in an alert window.
    alert(jq19().jquery);
})(jq17, jq19);

Adapter

What if the JavaScript is not already wrapped by a factory function, e.g. (function(…) { … })(…);

E.g., “version-legacy.js”:

alert($().jquery);

With Adapter, you can wrap existing JavaScripts files with any JavaScript fragments before and after the file:

<portlet>
    <name>jquery-version-legacy</name>
    <module>
        <script>
            <adapter>
                (function($){
                <include>/javascript/version-legacy.js</include>
                })(jq19);
            </adapter>
        </script>
        <depends>
            <module>jquery-1.9.0</module>
            <as>jq19</as>
        </depends>
    </module>
</portlet>

In case you already have many JavaScript files you want to re-use and don’t want to make extensive changes, or if a third-party library needs to be re-wrapped with JavaScript best practices, then Adapter is your friend.

Magic Behind the Scene

How can JBoss Portal Platform 6 accomplish all this?  The magic behind the scene is that JBoss Portal Platform 6 fully embraces Asynchronous Module Definition (AMD).  Behind the scenes, JBoss Portal Platform 6 translates the XML configurations into AMD friendly JavaScript.  For example, when loading both jQuery versions, JBoss Portal Platform 6 will generate the following JavaScript fragment:

define('PORTLET/jquery-portlet/jquery-portlet', ["SHARED/jquery","SHARED/jquery-1.9.0"], function(jq17,jq19) {
    var require = eXo.require, requirejs = eXo.require,define = eXo.define;
    eXo.define.names=["jq17","jq19"];
    eXo.define.deps=[jq17,jq19];
    return (function() {
        alert("jq17().jquery);
        alert("jq19().jquery)
    })(jq17, jq19);
});

Minify, Last-Modified

Last, if not least, JBoss Portal Platform 6 will automatically combine all of the JavaScripts in a single module and then minify the script.  This will not only reduce the size of the JavaScript, it will also reduce the number of files the user’s browser will need to download!  The minified resource will also have proper cache headers, such as Cache-Control and Last-Modified headers to reduce unnecessary re-download of the script and making it more CDN friendly.

Architecting Your Portal with JavaScript in Mind

With these enhancements to JBoss Portal Platform 6, it’s now possible to modularize your JavaScripts, apply dependency management, promote re-usability, and not to worry about the nitty gritty details behind the scenes.  It also opens up a number of possibilities such as deploying JavaScript libraries in a dedicated archive (.war), and portlets packaged in other archives can also reference and re-use the JavaScript.  If you need to upgrade the shared JavaScript code, you can simply deploy the archive containing the new script.

The Code

The examples in this article can be found on github.
https://github.com/saturnism/code-in-blogs/tree/master/jpp6-js-example

There are also plenty more examples in GateIn Community Project.
https://github.com/gatein/gatein-portal/tree/master/examples/portlets
(amd-js, jquery, and todomvc)


Read the original blog entry...

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