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https://issues.apache.org/jira/browse/LUCENE-3041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13804446#comment-13804446
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Uwe Schindler commented on LUCENE-3041:
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Hi I found a bug in the InvocationDispatcher when used with Java 7: the manual
ordering of methods to visit is broken, because Class#getDeclaredMethods()
returns the methods in random order (on same JVM, too). The ordering is not
enough to prevent choosing the wrong method, so AmbiguousMethodException occurs
("Multiple methods resolved for parameter type, cannot disambiguate"). In the
current code, because older JVMs return methods in declaration order and as
Collections.sort() is stable, the methods declared earlier take precendence.
But this does no longer work with Java 7.
If I have time, I will upload a fix I found for that (I have one locally in
another package, because this visitor was used for some internal code). The new
approach groups the visit(*) methods by parameter types with same superclass
and also sorts by class hierarchy distance (more far superclasses get lower
score than direct superclasses). The approch uses the lowest distance from
parameter type to method type.
This makes InvocationDispatcher randomization proof (just add
Collections.sort() in the InvocationDispatcher ctor to test...)
> Support Query Visting / Walking
> -------------------------------
>
> Key: LUCENE-3041
> URL: https://issues.apache.org/jira/browse/LUCENE-3041
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Affects Versions: 4.0-ALPHA
> Reporter: Chris Male
> Assignee: Simon Willnauer
> Priority: Minor
> Fix For: 4.6
>
> Attachments: LUCENE-3041.patch, LUCENE-3041.patch, LUCENE-3041.patch,
> LUCENE-3041.patch, LUCENE-3041.patch
>
>
> Out of the discussion in LUCENE-2868, it could be useful to add a generic
> Query Visitor / Walker that could be used for more advanced rewriting,
> optimizations or anything that requires state to be stored as each Query is
> visited.
> We could keep the interface very simple:
> {code}
> public interface QueryVisitor {
> Query visit(Query query);
> }
> {code}
> and then use a reflection based visitor like Earwin suggested, which would
> allow implementators to provide visit methods for just Querys that they are
> interested in.
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