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From Apache Wiki <wikidi...@apache.org>
Subject [Tapestry Wiki] Update of "Tapestry5AndJavaScriptExplained" by BobHarner
Date Mon, 17 Jan 2011 20:44:37 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Tapestry Wiki" for change notification.

The "Tapestry5AndJavaScriptExplained" page has been changed by BobHarner.
The comment on this change is: Partial updates to Tap 5.2, though still need to switch from
@IncludeJavaScriptLibrary to @Import annotation.
http://wiki.apache.org/tapestry/Tapestry5AndJavaScriptExplained?action=diff&rev1=6&rev2=7

--------------------------------------------------

  == Introduction ==
  
+ || Note: This page needs to be updated for Tapestry 5.2, including the @Import annotation
||
+ 
- Javascript is a critical element of modern web applications. Historically "real" software
developers have avoided JS either because they had more important things to do, or because
they simply didn't want to be bothered with front-end details. Well as we know, times have
changed and are changing still. If you want to have an application that can compete with other
modern applications, you have to use JS (including AJAX).
+ JavaScript is a critical element of modern web applications. Historically "real" software
developers have avoided JavaScript either because they had more important things to do, or
because they simply didn't want to be bothered with front-end details. Well as we know, times
have changed and are changing still. If you want to have an application that can compete with
other modern applications, you have to use JavaScript (including AJAX).
- Modern frameworks, and perhaps none more aggressively than [[http://www.rubyonrails.org/|RoR]],
go a long way in removing the pains of JS from developing web applications. Tapestry 5 is
no exception and even though it is currently in the beta stages, it has come along way in
making JS transparent to developers (not to mention 3rd party libraries like [[http://code.google.com/p/tapestry5-components/|tapestry5-components]]).
  
+ Modern frameworks, and perhaps none more aggressively than [[http://www.rubyonrails.org/|RoR]],
go a long way in removing the pains of JavaScript from developing web applications. Tapestry
5 is no exception and has come a long way in making JavaScript transparent to developers (not
to mention 3rd party libraries).
+ 
- However, there are brave souls who wish to know how it all works. Perhaps you're tracing
some weird error, developing a sophisticated component with JS, or maybe you're just curious.
This article is for such people, so we'll have a look at how Tapestry 5 elegantly weaves JS
into your application by creating a mixin. This mixin can be applied to links (that is, !PageLink
or !ActionLink components) so that the user will be asked to confirm that they would like
to follow that link, which is ultimately accomplished by a javascript `confirm` dialog.
+ However, there are brave souls who wish to know how it all works. Perhaps you're tracing
some weird error, developing a sophisticated component with JavaScript, or maybe you're just
curious. This article is for such people, so we'll have a look at how Tapestry 5 elegantly
weaves JavaScript into your application by creating a mixin. This mixin can be applied to
links (that is, !PageLink or !ActionLink components) so that the user will be asked to confirm
that they would like to follow that link, which is ultimately accomplished by a JavaScript
`confirm` dialog.
  
  ''The full project source is available [[http://thegodcode.net/tapestry5/jsclarity-project.zip|here]]''.
  
@@ -13, +16 @@

  
  This article assumes that you have some basic knowledge of Tapestry 5. You don't need intimate
knowledge of /how/ it works, just an understanding of how to develop applications with it.
In addition you should also be acquainted with the following concepts:
  
-  * Component [[http://tapestry.apache.org/tapestry5/guide/mixins.html|mixins]].
+  * [[http://tapestry.apache.org/component-mixins.html|Component Mixins]]
-  * Some javascript knowledge. You should at least have a basic understanding of client-side
objects and how they are created.
+  * Some JavaScript knowledge. You should at least have a basic understanding of client-side
objects and how they are created.
-  * Understanding of the [[http://json.org/|JSON]] format and the [[http://www.prototypejs.org/|prototype]]
library would be very helpful, but not required. A good starting point for modern JS programming
(prototype oriented, but still generally useful) is http://www.prototypejs.org/learn.
+  * Understanding of the [[http://json.org/|JSON]] format and the [[http://www.prototypejs.org/|prototype]]
library would be very helpful, but not required. A good starting point for modern JavaScript
programming (prototype oriented, but still generally useful) is http://www.prototypejs.org/learn.
  
  
  == Getting Started ==
  
- To start our project we'll use the [[http://tapestry.apache.org/tapestry5/quickstart/|maven
quickstart archetype]]. Assuming you have maven installed execute the following from a console:
+ To start our project we'll use the Maven quickstart archetype as described at [[http://tapestry.apache.org/getting-started.html|Getting
Started]]. Assuming you have Maven installed execute the following from a console:
  
  {{{
- mvn archetype:create -DarchetypeGroupId=org.apache.tapestry -DarchetypeArtifactId=quickstart
-DarchetypeVersion=5.0.11 -DgroupId=net.godcode -DartifactId=jsclarity -DpackageName=net.godcode.jsclarity
-Dversion=1.0.0-SNAPSHOT
+ mvn archetype:create -DarchetypeGroupId=org.apache.tapestry -DarchetypeArtifactId=quickstart
-DarchetypeVersion=5.0.11 -DgroupId=net.godcode -DartifactId=jsclarity -DpackageName=net.godcode.jsclarity
-Dversion=1.0.0-SNAPSHOT -DarchetypeRepository=http://tapestry.apache.or
  }}}
  
- I use maven 2, eclipse, the maven 2 eclipse plugin, and jetty (5) for my development environment.
I will make no assumptions about what you use, so when we create a class or run the application
I will simply say "create this class" or "run the application." I will however make note of
where certain files belong in the context of a maven project.
+ I use Maven 2, Eclipse, the Maven 2 Eclipse plugin, and Jetty (5) for my development environment.
I will make no assumptions about what you use, so when we create a class or run the application
I will simply say "create this class" or "run the application." I will however make note of
where certain files belong in the context of a Maven project.
  
  
  == Creating the Mixin ==
@@ -74, +77 @@

  }
  }}}
  
- The first thing you may ask is "What does the [[http://tapestry.apache.org/tapestry5/apidocs/org/apache/tapestry5/annotations/IncludeJavaScriptLibrary.html|@IncludeJavaScriptLibrary]]
do"? Naturally, it includes a javascript library, but we'll have a closer look at it later.
For now let's look at the `afterRender` method.
+ The first thing you may ask is "What does the [[http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/IncludeJavaScriptLibrary.html|@IncludeJavaScriptLibrary]]
do"? Naturally, it includes a JavaScript library, but we'll have a closer look at it later.
For now let's look at the `afterRender` method.
  
  {{{
  	@AfterRender
@@ -84, +87 @@

  	}
  }}}
  
- Here we do one thing: insert a little piece of javascript in our page. For now don't worry
about when/how/where this happens, just understand that this script code will be called after
the page has properly loaded in the user's browser. You'll notice that it's calling a constructor
(`new Confirm('%s', '%s');`) to create a client-side object of type `Confirm`. This javascript
class accompanies our mixin and implements the client-side logic to confirm that the user
would indeed like to proceed with the action.
+ Here we do one thing: insert a little piece of JavaScript in our page. For now don't worry
about when/how/where this happens, just understand that this script code will be called after
the page has properly loaded in the user's browser. You'll notice that it's calling a constructor
(`new Confirm('%s', '%s');`) to create a client-side object of type `Confirm`. This JavaScript
class accompanies our mixin and implements the client-side logic to confirm that the user
would indeed like to proceed with the action.
  
  
  == Creating the Mixin's Javascript File ==
  
- Now let's create our javascript class to accompany our mixin. Following the convention,
we'll place this file in the same package as our mixin class, such that it becomes a resource
on the classpath. This is useful because when we pass a relative name to the [[http://tapestry.apache.org/tapestry5/apidocs/org/apache/tapestry5/annotations/IncludeJavaScriptLibrary.html|@IncludeJavaScriptLibrary]],
Tapestry will start in the package of the annotated class.
+ Now let's create our JavaScript class to accompany our mixin. Following the convention,
we'll place this file in the same package as our mixin class, such that it becomes a resource
on the classpath. This is useful because when we pass a relative name to the [[http://tapestry.apache.org/tapestry5/apidocs/org/apache/tapestry5/annotations/IncludeJavaScriptLibrary.html|@IncludeJavaScriptLibrary]],
Tapestry will start in the package of the annotated class.
  
  ''Maven location: src/main/resources/net/godcode/jsclarity/mixins/confirm.js (notice this
is in `src/main/resources`)''
  
@@ -111, +114 @@

  }
  }}}
  
- Knowing a little about the prototype library will help you here, but in short, this is a
javascript class that takes 2 arguments in its constructor: the DOM id of the HTML element
(`element`) of which we will intercept `onclick` events, and the confirmation message (`message`)
to display when a click is received.
+ Knowing a little about the prototype library will help you here, but in short, this is a
JavaScript class that takes 2 arguments in its constructor: the DOM id of the HTML element
(`element`) of which we will intercept `onclick` events, and the confirmation message (`message`)
to display when a click is received.
  
  That's it, we're done writing our mixin. Now let's use it!
  
@@ -163, +166 @@

  
  == Understanding What's Happening ==
  
- At this point we've created a mixin and paired client-side functionality with it by creating
a javascript class in an external file. In doing so we've learned how to create this pairing,
make sure the script file is included in the rendered page, and how to create the client-side
object from the mixin. But how does it all fit together?
+ At this point we've created a mixin and paired client-side functionality with it by creating
a JavaScript class in an external file. In doing so we've learned how to create this pairing,
make sure the script file is included in the rendered page, and how to create the client-side
object from the mixin. But how does it all fit together?
  
  Let's start with what we know:
  
-  1. Ultimately a page comes down to HTML and javascript.
+  1. Ultimately a page comes down to HTML and JavaScript.
-  1. Our javascript class is in an external file, so that file must be included.
+  1. Our JavaScript class is in an external file, so that file must be included.
-  1. Our javascript class uses the prototype javascript library, so that must be included
before we include our javascript file.
+  1. Our JavaScript class uses the prototype JavaScript library, so that must be included
before we include our JavaScript file.
-  1. Because our javascript class needs the DOM id of an HTML element, that element must
be loaded before we instantiate an instance of our class.
+  1. Because our JavaScript class needs the DOM id of an HTML element, that element must
be loaded before we instantiate an instance of our class.
  
  Now view the source of the rendered page. It will look something like this:
  
@@ -220, +223 @@

  
  This annotation is a wonderful shortcut. To find where and how Tapestry implements the magic
behind it you'll need to dig into the T5 source. The beauty of course is that you don't need
to understand the ''how'' to understand what it does.
  
- You can apply this annotation to page, component, or mixin classes. You must provide it
with either the name of a javascript file as a string, or an array of files. These strings
represent locations in the classpath, which will be searched in a relative manner. Whenever
you use this annotation, Tapestry also adds the prototype and scriptaculous libraries before
the files specified in the annotation automatically. It's also smart enough not to add the
same file twice. To top it off, if your files cannot be found Tapestry will fail fast by throwing
an exception. To me, this is just great. I don't want my application to just suck it up and
keep going. The assumption made by Tapestry here is the same for any injected asset files:
that they are an integral part of the application's front end and so the breaking of the application
is a logical consequence when they are missing.
+ You can apply this annotation to page, component, or mixin classes. You must provide it
with either the name of a JavaScript file as a string, or an array of files. These strings
represent locations in the classpath, which will be searched in a relative manner. Whenever
you use this annotation, Tapestry also adds the prototype and scriptaculous libraries before
the files specified in the annotation automatically. It's also smart enough not to add the
same file twice. To top it off, if your files cannot be found Tapestry will fail fast by throwing
an exception. To me, this is just great. I don't want my application to just suck it up and
keep going. The assumption made by Tapestry here is the same for any injected asset files:
that they are an integral part of the application's front end and so the breaking of the application
is a logical consequence when they are missing.
  
  
  == RenderSupport ==
@@ -247, +250 @@

  </script>
  }}}
  
- That basically says it all. Calls to `RenderSupport#addScript` result in a `<script>`
block being generated at the foot of your page. If you want to see exactly what happens in
the javascript then you'll want to look at the `tapestry.js` file, where you can find the
source of `Tapestry.onDOMLoaded`. You could just take my word and know that the function argument
it receives is called after the document has loaded, effectively associating the contained
code with the `onload` event of the document. In our case we can know that the element to
which we are attaching our javascript object will have loaded. 
+ That basically says it all. Calls to `RenderSupport#addScript` result in a `<script>`
block being generated at the foot of your page. If you want to see exactly what happens in
the JavaScript then you'll want to look at the `tapestry.js` file, where you can find the
source of `Tapestry.onDOMLoaded`. You could just take my word and know that the function argument
it receives is called after the document has loaded, effectively associating the contained
code with the `onload` event of the document. In our case we can know that the element to
which we are attaching our JavaScript object will have loaded. 
  
  If multiple calls are made to `RenderSupport#addScript`, then the scripts will be accumulated
and output in a single call to `Tapestry.onDOMLoaded`.  Take note if you are calling `RenderSupport#addScript`
from a method used to restart the render cycle.  For instance, you could have a tree menu
component that uses an @AfterRender method to iterate over the list of tree nodes, while the
`RenderSupport#addScript` is used to initialize the tree.  Since you only want to initialize
the tree once, you may want to do something like this:
  

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