Package org.apache.calcite.util

Interface ReflectiveVisitDispatcher<R extends ReflectiveVisitor,E>

Type Parameters:

R - Return type

E - Argument type

public interface ReflectiveVisitDispatcher<R extends ReflectiveVisitor,E>

Interface for looking up methods relating to reflective visitation. One possible implementation would cache the results.

Type parameter 'R' is the base class of visitoR class; type parameter 'E' is the base class of visiteE class.

TODO: obsolete ReflectUtil.lookupVisitMethod(java.lang.Class<?>, java.lang.Class<?>, java.lang.String), and use caching in implementing that method.

Method Summary

Modifier and Type	Method	Description
boolean	invokeVisitor(R visitor, E visitee, String visitMethodName)	Implements the Glossary.VISITOR_PATTERN via reflection.
@Nullable Method	lookupVisitMethod(Class<? extends R> visitorClass, Class<? extends E> visiteeClass, String visitMethodName)	Looks up a visit method.
@Nullable Method	lookupVisitMethod(Class<? extends R> visitorClass, Class<? extends E> visiteeClass, String visitMethodName, List<Class> additionalParameterTypes)	Looks up a visit method taking additional parameters beyond the overloaded visitee type.

Method Details

lookupVisitMethod

@Nullable Method lookupVisitMethod(Class<? extends R> visitorClass,
 Class<? extends E> visiteeClass,
 String visitMethodName,
 List<Class> additionalParameterTypes)

Looks up a visit method taking additional parameters beyond the overloaded visitee type.

Parameters:

visitorClass - class of object whose visit method is to be invoked

visiteeClass - class of object to be passed as a parameter to the visit method

visitMethodName - name of visit method

additionalParameterTypes - list of additional parameter types

Returns:

method found, or null if none found

lookupVisitMethod

@Nullable Method lookupVisitMethod(Class<? extends R> visitorClass,
 Class<? extends E> visiteeClass,
 String visitMethodName)

Looks up a visit method.

Parameters:

visitorClass - class of object whose visit method is to be invoked

visiteeClass - class of object to be passed as a parameter to the visit method

visitMethodName - name of visit method

Returns:

method found, or null if none found

invokeVisitor

boolean invokeVisitor(R visitor,
 E visitee,
 String visitMethodName)

Implements the Glossary.VISITOR_PATTERN via reflection. The basic technique is taken from a Javaworld article. For an example of how to use it, see ReflectVisitorTest.

Visit method lookup follows the same rules as if compile-time resolution for VisitorClass.visit(VisiteeClass) were performed. An ambiguous match due to multiple interface inheritance results in an IllegalArgumentException. A non-match is indicated by returning false.

Parameters:

visitor - object whose visit method is to be invoked

visitee - object to be passed as a parameter to the visit method

visitMethodName - name of visit method, e.g. "visit"

Returns:

true if a matching visit method was found and invoked