Congratulations by the time you have reached this section, you probably have mastered the basics
of Ext-Scripting, you probably already can edit your local files and have them refreshed on the fly
Under normal circumstances you, should be set up by now and you can start coding happily.
However since this is a framework based reloading mechanism it is wise to dig a little bit deeper
and to know what is happening under the hood and why things behave like they do.
If you are interested then read on.
Additionally to the standard reloading feature, Ext-Scripting provides two components
which hopefully will make the life of every programmer easier.
The Compiler Output Component
The Change History Component
Note currently and for the foreseeable future only Facelets as page description language
will be supported by the components.
To use the components following namespace has to be included
Example
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One of the cornerstones of Ext-Scripting is the dynamic recompilation.
Every file changed, is reloaded, while you hit refresh on the browser.
Now, under normal circumstances, the compiler errors and warnings are written to the console log
as following:
Now, trying to catch those errors within the log is "mildly spoken" annoying
and time consuming.
Exactly for bypassing this problem a compiler output component
can be used either in your page or preferably in a second page.
The following Video shows the compiler output component in action
Video: Compiler Component in Action
Usage of the Compiler Output Component
The compiler output component currently is presented as Facelets only component as follows
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Following attributes can be used
Attribute Name
Possible Values
Description
errorsLabel
All values are allowed
A Label which is displayed in above all errors to notify the user that the error section
starts here
WarningsLabel
All values are allowed
A Label which is displayed in above all errors to notify the user that the warning
section
starts here
scriptingLanguage
Java, Groovy or an empty String
Scripting language filter, here you can set which scripting engines
compile errors should be displayed, currently Java or Groovy are supported as values
if you leave the attribute empty or set nothing then everything is displayed
Image: Compiler Output Component
The second cornerstone of Ext-Scripting is change tracking and dependency detection.
Now if you have changed a file, Ext-Scripting tracks the changes and also marks
most classes which have a dependency to your class as changed.
Again usually the output is pushed into the log as following:
Again, to get a quick overview within your running page, or preferably an extra page, you can use
a specialized component which gives you a quick overview over the change history of the system.
Here our change history component comes into play. With it you can track a certain number of changes
done over time including their marked dependencies.
Image: Change History Component in Action
Usage
The change history component can be currently used in Facelets only as follows
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Following attributes can be used
Attribute Name
Possible Values
Description
noEntries
The <Integer Value> number of entries of the current history
A positive Integer value which shows the last N entries of your history
beginning with the latest change marker on top
Ext-Scripting automatically compiles with the debug flags on. Debugging against a running configuration
should be no problem. If the debugger can be pointed towards the sources, debugging should work without
any side effects.
Due to the fact that the debugger can pick up the debug info from the newly compiled class
files. (Note - the class files are not altered in any way so in any case you just deal with normal Java
classes)
TODO add video here
One of the goals of Ext-Scripting is to prevent unnecessary restarts and redeploys during
development. To
enable this, it provides custom functionality outside of the scope of providing scripting
capabilities.
One of those features is the page and resource reloading from your source directories.
Pages and web-resources like CSS files or images are loaded from your resource directory without
having to redeploy the web
application,
changes on them can be watched on the fly simple by a browser reload. There is no need to adjust
your web application server or your IDE for auto deployment mechanisms. Unnecessary web application
restarts for changed resources can be avoided that way.
Note while page reloading works on the fly for both JSF 1.2 and JSF 2.x+, resource reloading
only works for JSF2.x+, if you need similar functionality for JSF 1.x you can use
a third party resource loading library like Weblets.
The central point of setting up your resource reloading are two configuration parameters
The first parameter org.apache.myfaces.extensions.scripting.resource.LOADER_PATHS defines
the root path for your resources (aka everything web related, like xhtml facelet templates css files etc..).
Note, despite being called resource LOADER_PATH in most cases this path will just be pointed
to the your source web application root directory.
(ie: src/main/webapp in a standard Maven2 structure or <project-root>/webapp for a standard
Eclipse project structure.
The name resource just refers to the fact that for Ext-Scripting every web related file is seen as resource
The second parameter facelets.RESOURCE_RESOLVER is responsible for enabling the resouce loading
of Facelet templates and pages, since Facelets does not have an auto plugging mechanism this has
to be
set to a standard value which is org.apache.myfaces.extensions.scripting.jsf.facelet.ReroutingResourceResolver
Ext-Scripting tries to avoid as many server restarts as possible. To enable this it needs to unload
recompile and load artifacts and the those which reference our changed ones. To enable this,
Ext-Scripting
does dependency detection on bytecode level as well as on artifact level. This functionality is enabled
automatically you wont have anything further to do. You can see it working by watching the output log,
if
you change a class, you automatically will see that the system marks the classes which reference your
changed class as tainted as well.
You have to have in mind that data currently in ram cannot be recovered by the unloading and reloading
happening, so everything stored for instance in application or session scope is lost that way.
Following video shows the mechanism working:
This dependency detection works over all dynamic classes, no matter being it classes, interfaces,
annotations, and it works over static and dynamic imports.
Javabean dependencies also are detected on artifact level so that if the JSF IOC mechanism is used those
bound over neutral Object classes also will reload the dependencies correctly.
One of the main features which Ext-Scripting provides over standard JSF is dynamic annotations.
Dynamic annotations basically introduces a mechanism so that your standard JSF annotations like
@ManagedBean or @FacesComponent or @ManagedProperty or even the scopes like @RequestScoped or
@SessionScoped
can be changed on the fly in a dynamic way.
To enable this mechanism you don't have to do anything, it comes out of the box in a MyFaces 2.0
environment.
Following video demonstrates the mechanism
Ext-Scripting supports following JSF 1.2 artifact reloading:
ApplicationFactory reloading on method call level
FacesContextFactory reloading on method call level
LifecycleFactory reloading on method call level
RenderkitFactory reloading on method call level
ElResolver
Converter (on JSF level alone)
Validator (on JSF level alone)
Component reloading on component tree creation level (on JSF level alone)
ViewHandler
Lifecycle
Renderer
PhaseListener
ManagedBeans reloading for all managed beans even session and application scoped ones on request
level
Support for either JavaC or JSR 199 depending on your JDK Version
Support for Groovy and Java
Ext-Scripting supports following JSF 2.0 artifact reloading: Additionally to what is present for JSF
1.2
Component limitations have been lifted for Facelets as rendering language
All major JSF 2 annotations can be used in a dynamic way, annotations can be moved removed or
added on the fly
Support for Reloading on ComponentTagHandler, ConverterTagHandler, BehaviorTagHandler,
ValidatorTagHandler
ResourceHandler
Behavior
BehaviorRenderer
ComponentSystemEvent Support via dynamic Annotations
Application System Event Support
While the target of supporting extension frameworks will be post 1.0 Ext-Scripting already
supports dynamic bean validation and Ext-Val
To setup Ext-Val simply add the needed dependencies and you can start to use it instantly
The MyFaces 2.0 demo has a simple example ported over from the Ext-Val distribution which
shows the dynamic aspects of using Ext-Val and Ext-Scripting combined
The same what applies to Ext-Val also applies to straight bean validation.
Note at the time of release, the current stable version of Ext-Val has a bug
which enforces one manual configuration entry!
org.apache.myfaces.extensions.scripting.startup.SuppressExtValWarningStartupListenerjavax.faces.event.PostConstructApplicationEvent
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Note the class already is provided by Ext-Scripting, all which has done is
to add this entry to bypass the error.
This class probably will be obsolete with Ext-Val versions higher than
2.0.3 (which was the latest stable at time of writing)
Currently there is no direct Spring support for Ext-Scripting, it however is in the works
and will be delivered in a release post 1.0
Currently there is no direct CDI support for Ext-Scripting, it however the
work on it will be started post 1.0
While Ext-Scripting itself is only used for rapid prototyping following two szenarii will probably occur in a typical
user development environment
while it makes sense to have the Groovy sources for editing, for the final deployment, it makes sense
to just deliver the classes instead of the source files.
While doing that for your ide is out of scope of this documentation (currently). The documentation can provide you the information on how
to do it in Apache Maven:
The trick is to combine two things. Apache Maven 2 profiles and the Apache Maven2 groovy plugin
For a short explanation on Apache Maven 2 profiles please follow this link: Apache Maven 2 Profiles
The idea is, to define a deployment profile which triggers the Maven 2 groovy plugin which then will compile your classes, here is an example
configuration of such a profile, which can be copy pasted into your build file
The standard settings of the groovy maven plugin is that it will use your src/main/groovy directory as the path to pickup the sources.
You either can use that one and adjust the corresponding org.apache.myfaces.extensions.scripting.groovy.LOADER_PATHS setting for editing.
Or you can readjust the corresponding plugin settings of the Groovy Maven plugin. Follow this link for further information.
A call to maven clean install -P deployment now triggers the groovy compile task. You also can use the extended features
of the maven profiles to automate the switch if you use maven also for deployment of your project.
One problem you might have noticed is, that if you do not work with the default configuration on your sources
(aka. WEB-INF/<scripting-language>, you have to rely on the corresponding configuration entries, which in itself take absolute paths.
One user of the system came up with the question, on how to deal with multiple developers. The answer is plain and simple, unfortunately the
support of such a use case could be better for 1.0, all you can do is either to rely on the default paths, or use your build system to handle
the configuration parts per user, or standardize on the same file structure for every user.
Additional support for this scenario will be added post 1.0 to ease this usecase but for now it is a known but not entirely solved problem.
