- /*
- * 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.
- */
-
- package org.apache.commons.jexl.util.introspection;
-
- 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 <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
- * @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
- * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
- * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
- * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
- * @version $Id: MethodMap.java,v 1.5 2004/08/19 17:15:59 dion Exp $
- */
- 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 String key
- * @return List list of methods
- */
- public List get(String key)
- {
- return (List) methodByNameMap.get(key);
- }
-
- /**
- * <p>
- * 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.
- * </p>
- *
- * <p>
- * This turns out to be a relatively rare case
- * where this is needed - however, functionality
- * like this is needed.
- * </p>
- *
- * @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 (Method)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 (Iterator applicable = applicables.iterator();
- applicable.hasNext();)
- {
- Method app = (Method) applicable.next();
- Class[] appArgs = app.getParameterTypes();
- boolean lessSpecific = false;
-
- for (Iterator maximal = maximals.iterator();
- !lessSpecific && maximal.hasNext();)
- {
- Method max = (Method) 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 (Method)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 (Iterator imethod = methods.iterator(); imethod.hasNext();)
- {
- Method method = (Method) imethod.next();
-
- 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 && 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;
- }
- }