Oracle Fusion Middleware Java API Reference for Oracle Extension SDK
11g Release 2 (



Declaration model.


Interface Summary
AnnotationD Represents an annotation (not to be confused with an annotation type).
ArrayTypeD Represents an array type.
ClassD Represents a primitive, class, interface, enum, or annotation type.
ConstructorD Represents a constructor.
Declaration Common supertype of all Declaration elements.
ExecutableD Common supertype for constructor and method declarations.
FieldD Represents a field or enum constant.
GenericD Common supertype for Declaration elements that may declare type parameters.
HasAnnotationsD Common supertype for Declaration elements that may have annotations.
HasNameD Common supertype for Declaration elements that have a name.
HasTypeD Common supertype for Declaration elements that have a type.
LocalVariableD Represents a local variable.
MemberD Represents a member declaration, part of a type declaration.
MethodD Represents a method or annotation element.
PackageD Represents a package.
ParameterD Represents a parameter.
TypeD Represents a type.
TypeVariableD Represents a type variable.
WildcardTypeD Represents a wildcard type.

Class Summary
Declaration.DeclarationKind Identifies a Declaration.

Package Description

Declaration model.

Similarities to reflection

Method names

This package's method names should match method names in reflection as closely as possible. This allows callers who are already familiar with reflection API to learn this API quicker. Examples: ClassD#getEnclosingMethod(), ClassD#getInterfaces(), GenericD#getTypeParameters().

Differences from reflection

No special getGeneric*() methods

Consider, for example, java.lang.reflect.Method#getReturnType() Method.getReturnType() . Though the return type of a method is a generic type, getReturnType() must return the type erasure of the return type for compatibility with callers compiled against the jdk < 1.5 reflection API. Thus, in order to get the real return type of a method in the jdk >= 1.5 reflection API, callers must call java.lang.reflect.Method#getGenericReturnType() Method.getGenericReturnType() .

This API is not bound by said requirement and is free to return the real return type of a method, generic or not. This trims down the size of the API and improves the readability of caller code that operates upon the real return type instead of the return type's erasure. We argue that the set of callers operating on the real return type form the majority. There is no loss of functionality because callers who want the type erasure can call getReturnType().getTypeErasure().

Non-empty TypeD

The jdk >= 1.5 reflection API requires that a caller casts a Type to be a Class (or other subtype) before calling methods such as getMethods() and isAssignableFrom(C). While technically correct, it is a very clunky API for IDE features to use. Because many of said operations are performed regardless of whether the target type is a class, type variable, wildcard type, array type, etc., these have been pushed into the supertype TypeD.

Here are some notable additions above what java.lang.Class provides:

The hidden clinit method

Though the reflection API does not provide access to the hidden clinit method, certain IDE features need access to it. In particular, debugging features require access to the method's line number table for determining if a breakpoint may be set on a particular line of code.

getName() returns simple names

All implementations of HasNameD#getName() should return simple names. The only place this deviates from the reflection API is that ClassD#getName() returns its simple name instead of java.lang.Class#getName() which returns a fully qualified class name or a FieldDescriptor name.

The benefit is that the name returned by ClassD#getName() conforms strictly to the JLS whereas the name returned by java.lang.Class#getName() conforms neither to the JLS nor the JVMS. To get the fully qualified source name of a class, use TypeD#getSourceName(), conformant to the JLS3. To get the fully qualified type descriptor of a class, use TypeD#getTypeDescriptor(), conformant to the JVMS3.


We use the method TypeD#getSourceName() instead of java.lang.Class#getCanonicalName(). The two problems posed by getCanonicalName() is that it is only valid on raw types and that JLS3 isn't out yet which means no one actually knows what "canonical name" means. The use of the term "source name" is both more readable and more general. It applies equally well to parameterized types, type variables, and wildcard types.

Never return a null String

A String typed method should NEVER return null if the specified value is not present. A String typed method may only return null if the method call itself is irrelevant. An example of where the reflection API returns a null String is java.lang.Package#getName() for the root package. Returning the empty string for the root package allows callers to fill a Map with PackageD values and PackageD#getSourceName() keys. However, it is unclear what to return for String typed methods where the result is irrelevant. Consider TypeD#getSourceName() for anonymous inner classes. An anonymous class may not be referred to in a source compilation unit, rendering the call to getSourceName() irrelevant. Returning null poses a problem preventing callers from filling a Map with TypeD values and the TypeD#getSourceName() keys. Special case handling decreases code readibility. However, returning the empty string also poses a problem because then two anonymous classes will share the same key.

We choose to return the empty string in this case with this reasoning. Consider that TypeD#getSourceName() uniquely identifies a type in a specific scope. That is, suppose there is a type variable T and a local class T both accessible at a given point in a source compilation unit. (Yes, that will generate a compile error but unlike the reflection API, this API must be able to handle erroneous compilation units.) However, one type will always hide the other, therefore it is safe to keep a Map of visible TypeD's at a given point in a source compilation unit. A refactoring feature, say, may want to be able to insert the value of getSourceName() into that given point in the source. If getSourceName() returns the empty string, then the caller will simple insert nothing into the buffer.

Oracle Fusion Middleware Java API Reference for Oracle Extension SDK
11g Release 2 (


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