Hello,
This is a follow up
of the WTP 2.0 Requirements meeting held on 26 Oct:
http://wiki.eclipse.org/index.php/2006-10-26_wtp-requiremements-minutes
I want to present
an overview of my vision how Java EE 5 models should be implemented in
WTP.
Currently, there
are J2EE 1.4 models implemented in WTP. These are EMF models generated
from the deployment descriptors' XML Schemas of the J2EE 1.4
specification. Overview of the J2EE 1.4 models is presented in the
following page:
http://www.eclipse.org/webtools/jst/components/j2ee/api/j2ee_models_overview.html
Java EE 5 models
should be implemented in a similar way. The EMF models should utilize
the new deployment descriptors' XML Schemas from the Java EE 5
specification. Additional complexity to the models is added by the fact
that the Java EE 5 specification uses Java Annotations in addition to
the deployment descriptors. Therefore, the problematic shifts on how to
integrate these annotations to the EMF model.
It was a natural
approach that I had a look to the JEM (Java EMF Model) project. JEM
contains functions for modeling Java classes in EMF. Unfortunately, JEM
does not cover Java Annotations at the moment and there is no plan for
the future yet:
http://dev.eclipse.org/newslists/news.eclipse.tools.ve/msg05989.html
There are to
approaches to model Java Annotations:
1. Extend JEM with new
features to cover Java Annotations and integrate both EMF models (the
other one is the one generated from the XML Schemas).
2. Implement custom
utility to parse and index Java Annotation from the source files and
make the EMF model (made from XML Schemas) to use it.
Due to the lack of
any documentation in the JEM project, approach 1. is feasible only
long-term. This is why I want to concentrate on approach 2.
Now, the Java EE 5
models problem can be split in the following tasks:
1. Build an EMF model
based on the deployment descriptors' XML Schemas.
2. Parse Java
Annotations from the Java files.
3. Index the parsed
annotations in a way they can be easily retrieved.
4. Make the EMF model
to be influenced by the available annotations.
5. Update Java
Annotation with changes on the EMF model.
Task 1. Build an
EMF model based on the deployment descriptors'' XML Schemas.
This can be done
easily with the available toolset provided by the EMF project. The EMF
model is generated by the XML Schemas for the Java EE 5 deployment
descriptors. A problem appears if we want to split the generated
classes in separate packages for better structure:
http://www.eclipse.org/newsportal/article.php?id=20770&group=eclipse.tools.emf#20770
However, this
problem is solvable at least with manual refactoring of the generated
classes.
Task 2. Parse Java
Annotations from the Java files.
Here Java files can
be:
- Java Class files
in JAR library in the classpath;
- Java source files
in the Eclipse project.
Java Annotations
from the Java Class files can be easily parsed using the Sun's Java
Reflect API.
Java Annotations from
the Java source files can be parsed using the Java DOM/AST API provided
by the Eclipse JDT Core project. The latter API models the Java source
code as a structured document. There, annotations are treated as member
modifiers (like public, private, static, final, etc.). There is a
function that checks if a modifier is an annotation.
The parser utility
will listen to events to trigger the parsing process:
-
ResourceChangeListener/Event - notifies for resource changes in the
workspace: project open/close, files added/deleted, etc;
-
ElementChangedListener/Event - notifies for changes in the Java Editor.
The parser will be notified that the user has changed a java file in
the editor and it has to be reparsed for changes in the annotations.
Task 3. Index the
parsed annotations in a way they can be easily retrieved.
The parser will update
an appropriate structure with the added or removed annotations. The
structure should allow quick and flexible way to retrieve the indexed
annotation. For beginning even an ArrayList that holds references to
the org.eclipse.jdt.core.dom.Annotation objects is enough. Annotation
objects hold references to the parent Java members and parent workspace
resources and that should be all the information we need. Of course,
the ArrayList is far away from the optimal solution and it should be
optimized later with a better structure.
Task 4. Make the
EMF model to be influenced by the available annotations.
The generated EMF
model from the deployment descriptors' XML Schemas will be modified in
a way that it not only looks into the XML data, but also looks up the
Annotation Model utility for the corresponding annotation. If there are
such annotations indexed, the EMF model will update it state
appropriately. The Annotation Model utility also has to provide
notification framework, so the EMF model to register a listener and be
notified with events on changes in the annotation model.
5. Update Java
Annotation with changes on the EMF model.
Properties in the EMF
model now declared in two sources: XML files and Java Annotations. When
this property is changes it has to be updated in the same source. If
the property is declared in XML then its new value has to be updated
again in the XML file. If the property is declared as a Java Annotation
it has to be updated again in the same Java Annotation.
To achieve the
above, the EMF model has to be changed in a way that it remembers the
source type of each property.
Updating Java
Annotation will be done again using the Java DOM/AST API.
This is the
overview for the moment. I want to here your comments. Especially, I
want to hear your opinion about the "Extending JEM" <--> "Custom
Annotation Model utility" dilemma. Due to the lack of documentation, my
knowledge to JEM is not enough and I cannot estimate the effort to
extend it with Java Annotation support. This is why I prefer the latter
approach that I have described in more details.
There are no
comments about the UI from my side for the moment. Here your comments
would be also interesting. Do we stick to the Deployment Descriptor
node in the Project Navigator? What features would be needed there for
future enhancements?
Greetings,
Kaloyan
Raev
Senior
Developer
NW AS
JS TOOLS JEE (BG)
SAP
Labs Bulgaria
T
+359/2/9157-416
mailto:kaloyan.raev@xxxxxxx
www.sap.com
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