org.eigenbase.util
Interface ReflectiveVisitDispatcher<R extends ReflectiveVisitor,E>

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.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/util/ReflectiveVisitDispatcher.java#4 $

Author:

Julian Hyde

Method Summary

boolean	invokeVisitor(R visitor, E visitee, String visitMethodName) Implements the Glossary.VisitorPattern via reflection.
Method	lookupVisitMethod(Class<? extends R> visitorClass, Class<? extends E> visiteeClass, String visitMethodName) Looks up a visit method.
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 Detail

lookupVisitMethod

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

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.VisitorPattern 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