org.apache.maven.shared.utils.introspection.MethodMap Maven / Gradle / Ivy
package org.apache.maven.shared.utils.introspection;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
/**
* @author Jason van Zyl
* @author Bob McWhirter
* @author Christoph Reck
* @author Geir Magnusson Jr.
* @author Attila Szegedi
* @version $Id$
*/
class MethodMap
{
private static final int MORE_SPECIFIC = 0;
private static final int LESS_SPECIFIC = 1;
private static final int INCOMPARABLE = 2;
/**
* Keep track of all methods with the same name.
*/
private final Map> methodByNameMap = new Hashtable>();
/**
* Add a method to a list of methods by name.
* For a particular class we are keeping track
* of all the methods with the same name.
*
* @param method The method
*/
void add( Method method )
{
String methodName = method.getName();
List l = get( methodName );
if ( l == null )
{
l = new ArrayList();
methodByNameMap.put( methodName, l );
}
l.add( method );
}
/**
* Return a list of methods with the same name.
*
* @param key The name of the method.
* @return List list of methods
*/
List get( String key )
{
return methodByNameMap.get( key );
}
/**
*
* Find a method. Attempts to find the
* most specific applicable method using the
* algorithm described in the JLS section
* 15.12.2 (with the exception that it can't
* distinguish a primitive type argument from
* an object type argument, since in reflection
* primitive type arguments are represented by
* their object counterparts, so for an argument of
* type (say) java.lang.Integer, it will not be able
* to decide between a method that takes int and a
* method that takes java.lang.Integer as a parameter.
*
*
*
* This turns out to be a relatively rare case
* where this is needed - however, functionality
* like this is needed.
*
*
* @param methodName name of method
* @param args the actual arguments with which the method is called
* @return the most specific applicable method, or null if no
* method is applicable.
* @throws AmbiguousException if there is more than one maximally
* specific applicable method
*/
Method find( String methodName, Object... args )
throws AmbiguousException
{
List methodList = get( methodName );
if ( methodList == null )
{
return null;
}
int l = args.length;
Class[] classes = new Class[l];
for ( int i = 0; i < l; ++i )
{
Object arg = args[i];
/*
* if we are careful down below, a null argument goes in there
* so we can know that the null was passed to the method
*/
classes[i] = arg == null ? null : arg.getClass();
}
return getMostSpecific( methodList, classes );
}
/**
* simple distinguishable exception, used when
* we run across ambiguous overloading
*/
static class AmbiguousException
extends Exception
{
}
private static Method getMostSpecific( List methods, Class... classes )
throws AmbiguousException
{
LinkedList applicables = getApplicables( methods, classes );
if ( applicables.isEmpty() )
{
return null;
}
if ( applicables.size() == 1 )
{
return applicables.getFirst();
}
/*
* This list will contain the maximally specific methods. Hopefully at
* the end of the below loop, the list will contain exactly one method,
* (the most specific method) otherwise we have ambiguity.
*/
LinkedList maximals = new LinkedList();
for ( Method app : applicables )
{
Class[] appArgs = app.getParameterTypes();
boolean lessSpecific = false;
for ( Iterator maximal = maximals.iterator(); !lessSpecific && maximal.hasNext(); )
{
Method max = maximal.next();
switch ( moreSpecific( appArgs, max.getParameterTypes() ) )
{
case MORE_SPECIFIC:
{
/*
* This method is more specific than the previously
* known maximally specific, so remove the old maximum.
*/
maximal.remove();
break;
}
case LESS_SPECIFIC:
{
/*
* This method is less specific than some of the
* currently known maximally specific methods, so we
* won't add it into the set of maximally specific
* methods
*/
lessSpecific = true;
break;
}
}
}
if ( !lessSpecific )
{
maximals.addLast( app );
}
}
if ( maximals.size() > 1 )
{
// We have more than one maximally specific method
throw new AmbiguousException();
}
return maximals.getFirst();
}
/**
* Determines which method signature (represented by a class array) is more
* specific. This defines a partial ordering on the method signatures.
*
* @param c1 first signature to compare
* @param c2 second signature to compare
* @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if
* c1 is less specific than c2, INCOMPARABLE if they are incomparable.
*/
private static int moreSpecific( Class[] c1, Class[] c2 )
{
boolean c1MoreSpecific = false;
boolean c2MoreSpecific = false;
for ( int i = 0; i < c1.length; ++i )
{
if ( c1[i] != c2[i] )
{
c1MoreSpecific = c1MoreSpecific || isStrictMethodInvocationConvertible( c2[i], c1[i] );
c2MoreSpecific = c2MoreSpecific || isStrictMethodInvocationConvertible( c1[i], c2[i] );
}
}
if ( c1MoreSpecific )
{
if ( c2MoreSpecific )
{
/*
* Incomparable due to cross-assignable arguments (i.e.
* foo(String, Object) vs. foo(Object, String))
*/
return INCOMPARABLE;
}
return MORE_SPECIFIC;
}
if ( c2MoreSpecific )
{
return LESS_SPECIFIC;
}
/*
* Incomparable due to non-related arguments (i.e.
* foo(Runnable) vs. foo(Serializable))
*/
return INCOMPARABLE;
}
/**
* Returns all methods that are applicable to actual argument types.
*
* @param methods list of all candidate methods
* @param classes the actual types of the arguments
* @return a list that contains only applicable methods (number of
* formal and actual arguments matches, and argument types are assignable
* to formal types through a method invocation conversion).
*/
private static LinkedList getApplicables( List methods, Class... classes )
{
LinkedList list = new LinkedList();
for ( Method method : methods )
{
if ( isApplicable( method, classes ) )
{
list.add( method );
}
}
return list;
}
/**
* Returns true if the supplied method is applicable to actual
* argument types.
*
* @param method The method to check for applicability
* @param classes The arguments
* @return true if the method applies to the parameter types
*/
private static boolean isApplicable( Method method, Class... classes )
{
Class[] methodArgs = method.getParameterTypes();
if ( methodArgs.length != classes.length )
{
return false;
}
for ( int i = 0; i < classes.length; ++i )
{
if ( !isMethodInvocationConvertible( methodArgs[i], classes[i] ) )
{
return false;
}
}
return true;
}
/**
* Determines whether a type represented by a class object is
* convertible to another type represented by a class object using a
* method invocation conversion, treating object types of primitive
* types as if they were primitive types (that is, a Boolean actual
* parameter type matches boolean primitive formal type). This behavior
* is because this method is used to determine applicable methods for
* an actual parameter list, and primitive types are represented by
* their object duals in reflective method calls.
*
* @param formal the formal parameter type to which the actual
* parameter type should be convertible
* @param actual the actual parameter type.
* @return true if either formal type is assignable from actual type,
* or formal is a primitive type and actual is its corresponding object
* type or an object type of a primitive type that can be converted to
* the formal type.
*/
private static boolean isMethodInvocationConvertible( Class formal, Class actual )
{
/*
* if it's a null, it means the arg was null
*/
if ( actual == null && !formal.isPrimitive() )
{
return true;
}
/*
* Check for identity or widening reference conversion
*/
if ( actual != null && formal.isAssignableFrom( actual ) )
{
return true;
}
/*
* Check for boxing with widening primitive conversion. Note that
* actual parameters are never primitives.
*/
if ( formal.isPrimitive() )
{
if ( formal == Boolean.TYPE && actual == Boolean.class )
{
return true;
}
if ( formal == Character.TYPE && actual == Character.class )
{
return true;
}
if ( formal == Byte.TYPE && actual == Byte.class )
{
return true;
}
if ( formal == Short.TYPE && ( actual == Short.class || actual == Byte.class ) )
{
return true;
}
if ( formal == Integer.TYPE
&& ( actual == Integer.class || actual == Short.class || actual == Byte.class ) )
{
return true;
}
if ( formal == Long.TYPE
&& ( actual == Long.class || actual == Integer.class || actual == Short.class
|| actual == Byte.class ) )
{
return true;
}
if ( formal == Float.TYPE
&& ( actual == Float.class || actual == Long.class || actual == Integer.class
|| actual == Short.class || actual == Byte.class ) )
{
return true;
}
if ( formal == Double.TYPE
&& ( actual == Double.class || actual == Float.class || actual == Long.class || actual == Integer.class
|| actual == Short.class || actual == Byte.class ) )
{
return true;
}
}
return false;
}
/**
* Determines whether a type represented by a class object is
* convertible to another type represented by a class object using a
* method invocation conversion, without matching object and primitive
* types. This method is used to determine the more specific type when
* comparing signatures of methods.
*
* @param formal the formal parameter type to which the actual
* parameter type should be convertible
* @param actual the actual parameter type.
* @return true if either formal type is assignable from actual type,
* or formal and actual are both primitive types and actual can be
* subject to widening conversion to formal.
*/
private static boolean isStrictMethodInvocationConvertible( Class formal, Class actual )
{
/*
* we shouldn't get a null into, but if so
*/
if ( actual == null && !formal.isPrimitive() )
{
return true;
}
/*
* Check for identity or widening reference conversion
*/
if ( formal.isAssignableFrom( actual ) )
{
return true;
}
/*
* Check for widening primitive conversion.
*/
if ( formal.isPrimitive() )
{
if ( formal == Short.TYPE && ( actual == Byte.TYPE ) )
{
return true;
}
if ( formal == Integer.TYPE && ( actual == Short.TYPE || actual == Byte.TYPE ) )
{
return true;
}
if ( formal == Long.TYPE && ( actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE ) )
{
return true;
}
if ( formal == Float.TYPE
&& ( actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE ) )
{
return true;
}
if ( formal == Double.TYPE
&& ( actual == Float.TYPE || actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE
|| actual == Byte.TYPE ) )
{
return true;
}
}
return false;
}
}
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