javax.lang.model.element.AnnotationValueVisitor Maven / Gradle / Ivy
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*
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package javax.lang.model.element;
import java.util.List;
import javax.lang.model.type.TypeMirror;
/**
* A visitor of the values of annotation type elements, using a
* variant of the visitor design pattern. Unlike a standard visitor
* which dispatches based on the concrete type of a member of a type
* hierarchy, this visitor dispatches based on the type of data
* stored; there are no distinct subclasses for storing, for example,
* {@code boolean} values versus {@code int} values. Classes
* implementing this interface are used to operate on a value when the
* type of that value is unknown at compile time. When a visitor is
* passed to a value's {@link AnnotationValue#accept accept} method,
* the visitXyz method applicable to that value is
* invoked.
*
* Classes implementing this interface may or may not throw a
* {@code NullPointerException} if the additional parameter {@code p}
* is {@code null}; see documentation of the implementing class for
* details.
*
*
WARNING: It is possible that methods will be added to
* this interface to accommodate new, currently unknown, language
* structures added to future versions of the Java™ programming
* language. Therefore, visitor classes directly implementing this
* interface may be source incompatible with future versions of the
* platform. To avoid this source incompatibility, visitor
* implementations are encouraged to instead extend the appropriate
* abstract visitor class that implements this interface. However, an
* API should generally use this visitor interface as the type for
* parameters, return type, etc. rather than one of the abstract
* classes.
*
*
Note that methods to accommodate new language constructs could
* be added in a source compatible way if they were added as
* default methods. However, default methods are only
* available on Java SE 8 and higher releases and the {@code
* javax.lang.model.*} packages bundled in Java SE 8 were required to
* also be runnable on Java SE 7. Therefore, default methods
* were not used when extending {@code javax.lang.model.*}
* to cover Java SE 8 language features. However, default methods
* are used in subsequent revisions of the {@code javax.lang.model.*}
* packages that are only required to run on Java SE 8 and higher
* platform versions.
*
* @param the return type of this visitor's methods
* @param the type of the additional parameter to this visitor's methods.
* @author Joseph D. Darcy
* @author Scott Seligman
* @author Peter von der Ahé
* @since 1.6
*/
public interface AnnotationValueVisitor {
/**
* Visits an annotation value.
* @param av the value to visit
* @param p a visitor-specified parameter
* @return a visitor-specified result
*/
R visit(AnnotationValue av, P p);
/**
* A convenience method equivalent to {@code visit(av, null)}.
*
* @implSpec The default implementation is {@code visit(av, null)}.
*
* @param av the value to visit
* @return a visitor-specified result
*/
default R visit(AnnotationValue av) {
return visit(av, null);
}
/**
* Visits a {@code boolean} value in an annotation.
* @param b the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitBoolean(boolean b, P p);
/**
* Visits a {@code byte} value in an annotation.
* @param b the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitByte(byte b, P p);
/**
* Visits a {@code char} value in an annotation.
* @param c the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitChar(char c, P p);
/**
* Visits a {@code double} value in an annotation.
* @param d the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitDouble(double d, P p);
/**
* Visits a {@code float} value in an annotation.
* @param f the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitFloat(float f, P p);
/**
* Visits an {@code int} value in an annotation.
* @param i the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitInt(int i, P p);
/**
* Visits a {@code long} value in an annotation.
* @param i the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitLong(long i, P p);
/**
* Visits a {@code short} value in an annotation.
* @param s the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitShort(short s, P p);
/**
* Visits a string value in an annotation.
* @param s the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitString(String s, P p);
/**
* Visits a type value in an annotation.
* @param t the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitType(TypeMirror t, P p);
/**
* Visits an {@code enum} value in an annotation.
* @param c the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitEnumConstant(VariableElement c, P p);
/**
* Visits an annotation value in an annotation.
* @param a the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitAnnotation(AnnotationMirror a, P p);
/**
* Visits an array value in an annotation.
* @param vals the value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
*/
R visitArray(List vals, P p);
/**
* Visits an unknown kind of annotation value.
* This can occur if the language evolves and new kinds
* of value can be stored in an annotation.
* @param av the unknown value being visited
* @param p a visitor-specified parameter
* @return the result of the visit
* @throws UnknownAnnotationValueException
* a visitor implementation may optionally throw this exception
*/
R visitUnknown(AnnotationValue av, P p);
}