com.bluegosling.reflect

Interface TypeVisitor<R,P>

Type Parameters:

R - the type of value returned from visiting a type

P - an optional context parameter that is supplied to the visitor when visiting a type

public interface TypeVisitor<R,P>

A visitor for generic types. This enables dynamic-dispatch-like algorithms without the if-else boiler-plate with instanceof checks and casts. To visit a type, use the main entry-point method: visit(Type, Object).

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	TypeVisitor.Builder<R,P> A builder of visitors, using functional interfaces as the building blocks.

Method Summary

Modifier and Type	Method and Description
default R	defaultAction(Type type, P param) The default action for visiting a type, called when visiting a type where the corresponding visit* method has not been overridden.
default R	visit(Type type, P param) Visits the given type.
default R	visitClass(Class<?> clazz, P param) Invoked when the visited type is a class token.
default R	visitGenericArrayType(GenericArrayType arrayType, P param) Invoked when the visited type is a generic array type.
default R	visitParameterizedType(ParameterizedType parameterizedType, P param) Invoked when the visited type is a parameterized type.
default R	visitTypeVariable(TypeVariable<?> typeVariable, P param) Invoked when the visited type is a type variable.
default R	visitUnknownType(Type type, P param) Invoked when the visited type is not a known sub-type of the Type interface.
default R	visitWildcardType(WildcardType wildcardType, P param) Invoked when the visited type is a wildcard type.

Method Detail

visit

default R visit(Type type,
                P param)

Visits the given type. This is the entry point and generally need not be overridden by implementing classes. This method will re-dispatch to one of the other visit methods based on the kind of given type.

Parameters:

type - the type

param - the context parameter

Returns:

the result of visiting the given type

defaultAction

default R defaultAction(Type type,
                        P param)

The default action for visiting a type, called when visiting a type where the corresponding visit* method has not been overridden.

The default implementation returns null.

Parameters:

type - a generic type

param - the context parameter

Returns:

the result of visiting the given type

visitClass

default R visitClass(Class<?> clazz,
                     P param)

Invoked when the visited type is a class token.

Parameters:

clazz - the class token

param - the context parameter

Returns:

the result of visiting the given class

visitParameterizedType

default R visitParameterizedType(ParameterizedType parameterizedType,
                                 P param)

Invoked when the visited type is a parameterized type.

Parameters:

parameterizedType - the parameterized type

param - the context parameter

Returns:

the result of visiting the given parameterized type

visitGenericArrayType

default R visitGenericArrayType(GenericArrayType arrayType,
                                P param)

Invoked when the visited type is a generic array type.

Parameters:

arrayType - the generic array type

param - the context parameter

Returns:

the result of visiting the given generic array type

visitWildcardType

default R visitWildcardType(WildcardType wildcardType,
                            P param)

Invoked when the visited type is a wildcard type.

Parameters:

wildcardType - the wildcard type

param - the context parameter

Returns:

the result of visiting the given wildcard type

visitTypeVariable

default R visitTypeVariable(TypeVariable<?> typeVariable,
                            P param)

Invoked when the visited type is a type variable.

Parameters:

typeVariable - the type variable

param - the context parameter

Returns:

the result of visiting the given type variable

visitUnknownType

default R visitUnknownType(Type type,
                           P param)

Invoked when the visited type is not a known sub-type of the Type interface.

Other visit* methods have a default implementation that calls defaultAction(Type, Object). But the default implementation of this method is different. Instead, it throws an UnknownTypeException.

Parameters:

type - the type

param - the context parameter

Returns:

the result of visiting the given type