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package org.codehaus.plexus.util.introspection;

/*
 * Copyright The Codehaus 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;

/**
 * @author Jason van Zyl
 * @author Bob McWhirter
 * @author Christoph Reck
 * @author Geir Magnusson Jr.
 * @author Attila Szegedi
 *
 */
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.
     * 
     * @param method The method
     */
    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 name of the method.
     * @return List 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 ( Object method1 : methods ) { Method method = (Method) method1; 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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