Difference between revisions of "MoDisco/Components/J2SE5"

Revision as of 09:13, 16 March 2009

The J2SE5 metamodel : it is the reflect of Java language, as it has been defined in version 3 of "Java Language Specification" from Sun Microsystems ("JLS3" corresponds to JDK 5).

J2SE5 metamodel contains 101 metaclasses. To better understand it, this page will introduce main features (metaclasses and links).

You could also browse definition model, j2se5.ecore available in sources (see install section).

A good tip is also to see javadoc associated to metamodel implemented by Eclipse team in project JDT (Java Development Tool). This metamodel and J2SE5 are very similar.

Main metaclasses

ASTNode

Every metaclasses (without metaclass Model) inherit from ASTNode. As its name indicate it, ASTNode represent a graph node. ASTNode has a reference to Comment metaclass because almost every java element could be associated to a comment (bloc or line comment and Javadoc). More details in "Comment" section.

ASTNode metaclass

Model, Package, AbstractTypeDeclaration

Root element of each J2SE5 model in an instance of "Model" metaclass. It is a translation of java application concept, so it contains package declarations (instances of PackageDeclaration metaclass). And package declarations contain type declarations (instances compatible with AbstractTypeDeclaration metaclass), and so on ...

Model, Package & type declaration superclass

NamedElement & notion of Proxy

A lot of java elements are "named", and this name could be considered as an identifier : methods, packages, types, variables, fields, ... So all of corresponding metaclasses inherit from NamedElement metaclass. It will be usefull to resolve references in binding, see NamedElementRef metaclass.

And an other goal of this metaclass is to indicate which element is a part of the current java application or not (element from an external library of from JDK). Then external elements are tagged as proxy through dedicated attribute and could be easily filtered. For example, instruction "System.out.println" has been decomposed in three named elements (one class, one variable and one method) which defintion are not part of current java application. So attribute "proxy" of these elements has been initialized as true.

NamedElement and its hierarchy

NamedElementRef

To represent links between java elements, as java AST defines only string references, metaclass NamedElementRef initially contained only this information. But an important addition was to resolve binding between elements, so is is actually possible to navigate directly in elements graph. It has been represented through a relationship from a NamedElementRef to a NamedElement (proxy or not).

NamedElementRef

BodyDeclaration

A type declaration has different kinds of contents : fields, methods, static block, initialization block or other type declarations. All of these elements are of type BodyDeclaration metaclass.

BodyDeclaration and its hierarchy

Expressions

Like in many languages, concept of expression exists in Java : it is a portion of code, without declarations, and its evaluation returns a value, numerical or boolean or other ...

++i

All types of expressions shall inherit from Expression metaclass.

Expression and its hierarchy

Statements

An "instruction" in Java is represented by Statement metaclass. A block of code (Block metaclass) contains a collection of statements, an a block of code may be contained by a method.

if, while, for, do, ...

All of their definitions use concept of expression to separate value from instruction keyword.

Statement and its hierarchy

Zoom on comments

There is three kinds of comments : line comments (//), block comments (/* */) and javadoc (/** */). Every comments contains text fragments, but we could have more informations on javadoc (Javadoc metaclass), it could contain javadoc tags that are identified and collected through instances of TagElement metaclass.

Comment and its hierarchy

Zoom on annotations

Official usage of annotations has been introduced in version 5 of JDK. To handle it, annotation declarations are managed as type declarations (AnnotationTypeDeclaration metaclass) with specific attributes (AnnotationTypeMemberDeclaration metaclass). And annotation usages are translated in instances of Annotation metaclass, which reference corresponding annotation declarations. And parameters are translated in instances of MemberValuePair metaclass.

Annotation

Zoom on generics

Version 5 of JDK introduces also concept of "generics". Generic types of methods declarations are translated respectively in instances of TypeDeclaration of MethodDeclaration metaclass with arguments as instances of TypeParameter metaclass. Usage of these generics are translated in instances of ParameterizedType metaclass which reference concret elements (type and types arguments).

Specific case of type argument is "wildcard" (for example <? extends X>. There is a specific metaclass to handle it : WildCardType.

Generics

Requirements

To use the plug-in you need:

• JDK 1.5 or above
• a version of Eclipse 3.3 or above with the following set of plugins installed

• EMF 2.3.0 or higher

Team

Gabriel Barbier (Mia-Software)

Fabien Giquel (Mia-Software)

Frédéric Madiot (Mia-Software)

Install

You will find a version of this plug-in attached in following bug.

As IP review of this plugin is not finished, here is installation instructions :

• Extract archive file in your Eclipse workspace, then use "import" menu to import this project.
• Use "export" menu to export this project as a plugin (Deployable plugins and fragments) in your Eclipse installation. Don't forget to choose "Package plug-ins as individual jar archives" option.
• re-start your Eclipse to take in account this plug-in

Associated Discoverers

The main discoverer available for this metamodel : JavaDiscoverer

It also exists an other project which produces a very similar model of Java applications : JavaAST I hope these two discoverers will be merged in futur.