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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