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package org.codehaus.plexus.interpolation.reflection;

/* ====================================================================
 *   Copyright 2001-2004 The Apache Software Foundation.
 *
 *   Licensed 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;

/**
 * NOTE: This class was copied from plexus-utils, to allow this library
 * to stand completely self-contained.
 * 
* @author Jason van Zyl * @author Bob McWhirter * @author Christoph Reck * @author Geir Magnusson Jr. * @author Attila Szegedi * @version $Id$ */ public 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. */ 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. */ public 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 key * @return list of methods */ public 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 */ public 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 */ public 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. */ 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 ) { return actual == Boolean.class; } if ( formal == Character.TYPE ) { return actual == Character.class; } if ( formal == Byte.TYPE ) { return actual == Byte.class; } if ( formal == Short.TYPE ) { return actual == Short.class || actual == Byte.class; } if ( formal == Integer.TYPE ) { return actual == Integer.class || actual == Short.class || actual == Byte.class; } if ( formal == Long.TYPE ) { return actual == Long.class || actual == Integer.class || actual == Short.class || actual == Byte.class; } if ( formal == Float.TYPE ) { return actual == Float.class || actual == Long.class || actual == Integer.class || actual == Short.class || actual == Byte.class; } if ( formal == Double.TYPE ) { return actual == Double.class || actual == Float.class || actual == Long.class || actual == Integer.class || actual == Short.class || actual == Byte.class; } } 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 ) { return actual == Byte.TYPE; } if ( formal == Integer.TYPE ) { return actual == Short.TYPE || actual == Byte.TYPE; } if ( formal == Long.TYPE ) { return actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE; } if ( formal == Float.TYPE ) { return actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE; } if ( formal == Double.TYPE ) { return actual == Float.TYPE || actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE; } } return false; } }




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