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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.commons.jexl.util.introspection;
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import java.lang.reflect.Method;
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import java.util.ArrayList;
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import java.util.Hashtable;
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import java.util.Iterator;
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import java.util.LinkedList;
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import java.util.List;
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* @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
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* @author <a href="mailto:bob@werken.com">Bob McWhirter</a>
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* @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a>
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* @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
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* @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a>
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* @version $Id: MethodMap.java 584046 2007-10-12 05:14:37Z proyal $
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public class MethodMap {
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* whether a method is more specific than a previously compared one.
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private static final int MORE_SPECIFIC = 0;
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* whether a method is less specific than a previously compared one.
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private static final int LESS_SPECIFIC = 1;
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* A method doesn't match a previously compared one.
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private static final int INCOMPARABLE = 2;
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* Keep track of all methods with the same name.
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Map methodByNameMap = new Hashtable();
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* Add a method to a list of methods by name. For a particular class we are
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* keeping track of all the methods with the same name.
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* @param method the method.
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public void add(Method method) {
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String methodName = method.getName();
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List l = get(methodName);
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methodByNameMap.put(methodName, l);
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* Return a list of methods with the same name.
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* @return List list of methods
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public List get(String key) {
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return (List) methodByNameMap.get(key);
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* Find a method. Attempts to find the
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* most specific applicable method using the
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* algorithm described in the JLS section
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* 15.12.2 (with the exception that it can't
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* distinguish a primitive type argument from
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* an object type argument, since in reflection
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* primitive type arguments are represented by
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* their object counterparts, so for an argument of
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* type (say) java.lang.Integer, it will not be able
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* to decide between a method that takes int and a
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* method that takes java.lang.Integer as a parameter.
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* This turns out to be a relatively rare case
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* where this is needed - however, functionality
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* like this is needed.
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* @param methodName name of method
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* @param args the actual arguments with which the method is called
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* @return the most specific applicable method, or null if no
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* method is applicable.
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* @throws AmbiguousException if there is more than one maximally
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* specific applicable method
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public Method find(String methodName, Object[] args)
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throws AmbiguousException {
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List methodList = get(methodName);
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if (methodList == null) {
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Class[] classes = new Class[l];
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for (int i = 0; i < l; ++i) {
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Object arg = args[i];
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* if we are careful down below, a null argument goes in there
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* so we can know that the null was passed to the method
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arg == null ? null : arg.getClass();
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return getMostSpecific(methodList, classes);
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* Simple distinguishable exception, used when
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* we run across ambiguous overloading. Caught
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* by the introspector.
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public static class AmbiguousException extends RuntimeException {
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* Version Id for serializable
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private static final long serialVersionUID = -2314636505414551663L;
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private static Method getMostSpecific(List methods, Class[] classes)
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throws AmbiguousException {
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LinkedList applicables = getApplicables(methods, classes);
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if (applicables.isEmpty()) {
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if (applicables.size() == 1) {
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return (Method) applicables.getFirst();
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* This list will contain the maximally specific methods. Hopefully at
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* the end of the below loop, the list will contain exactly one method,
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* (the most specific method) otherwise we have ambiguity.
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LinkedList maximals = new LinkedList();
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for (Iterator applicable = applicables.iterator();
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applicable.hasNext();) {
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Method app = (Method) applicable.next();
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Class[] appArgs = app.getParameterTypes();
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boolean lessSpecific = false;
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for (Iterator maximal = maximals.iterator();
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!lessSpecific && maximal.hasNext();) {
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Method max = (Method) maximal.next();
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switch (moreSpecific(appArgs, max.getParameterTypes())) {
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case MORE_SPECIFIC: {
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* This method is more specific than the previously
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* known maximally specific, so remove the old maximum.
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case LESS_SPECIFIC: {
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* This method is less specific than some of the
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* currently known maximally specific methods, so we
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* won't add it into the set of maximally specific
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maximals.addLast(app);
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if (maximals.size() > 1) {
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// We have more than one maximally specific method
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throw new AmbiguousException();
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return (Method) maximals.getFirst();
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* Determines which method signature (represented by a class array) is more
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* specific. This defines a partial ordering on the method signatures.
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* @param c1 first signature to compare
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* @param c2 second signature to compare
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* @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if
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* c1 is less specific than c2, INCOMPARABLE if they are incomparable.
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private static int moreSpecific(Class[] c1, Class[] c2) {
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boolean c1MoreSpecific = false;
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boolean c2MoreSpecific = false;
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// compare lengths to handle comparisons where the size of the arrays
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// doesn't match, but the methods are both applicable due to the fact
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// that one is a varargs method
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if (c1.length > c2.length) {
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return MORE_SPECIFIC;
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if (c2.length > c1.length) {
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return LESS_SPECIFIC;
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// ok, move on and compare those of equal lengths
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for (int i = 0; i < c1.length; ++i) {
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if (c1[i] != c2[i]) {
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boolean last = (i == c1.length - 1);
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isStrictConvertible(c2[i], c1[i], last);
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isStrictConvertible(c1[i], c2[i], last);
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if (c1MoreSpecific) {
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if (c2MoreSpecific) {
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* Incomparable due to cross-assignable arguments (i.e.
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* foo(String, Object) vs. foo(Object, String))
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return MORE_SPECIFIC;
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if (c2MoreSpecific) {
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return LESS_SPECIFIC;
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* Incomparable due to non-related arguments (i.e.
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* foo(Runnable) vs. foo(Serializable))
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* Returns all methods that are applicable to actual argument types.
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* @param methods list of all candidate methods
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* @param classes the actual types of the arguments
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* @return a list that contains only applicable methods (number of
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* formal and actual arguments matches, and argument types are assignable
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* to formal types through a method invocation conversion).
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private static LinkedList getApplicables(List methods, Class[] classes) {
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LinkedList list = new LinkedList();
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for (Iterator imethod = methods.iterator(); imethod.hasNext();) {
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Method method = (Method) imethod.next();
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if (isApplicable(method, classes)) {
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* Returns true if the supplied method is applicable to actual
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* @param method method that will be called
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* @param classes arguments to method
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* @return true if method is applicable to arguments
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private static boolean isApplicable(Method method, Class[] classes) {
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Class[] methodArgs = method.getParameterTypes();
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if (methodArgs.length > classes.length) {
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// if there's just one more methodArg than class arg
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// and the last methodArg is an array, then treat it as a vararg
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return methodArgs.length == classes.length + 1 &&
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methodArgs[methodArgs.length - 1].isArray();
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if (methodArgs.length == classes.length) {
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// this will properly match when the last methodArg
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// is an array/varargs and the last class is the type of array
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// (e.g. String when the method is expecting String...)
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for (int i = 0; i < classes.length; ++i) {
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if (!isConvertible(methodArgs[i], classes[i], false)) {
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// if we're on the last arg and the method expects an array
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if (i == classes.length - 1 && methodArgs[i].isArray()) {
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// check to see if the last arg is convertible
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// to the array's component type
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return isConvertible(methodArgs[i], classes[i], true);
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if (methodArgs.length > 0) {// more arguments given than the method accepts; check for varargs
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// check that the last methodArg is an array
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Class lastarg = methodArgs[methodArgs.length - 1];
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if (!lastarg.isArray()) {
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// check that they all match up to the last method arg
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for (int i = 0; i < methodArgs.length - 1; ++i) {
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if (!isConvertible(methodArgs[i], classes[i], false)) {
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// check that all remaining arguments are convertible to the vararg type
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Class vararg = lastarg.getComponentType();
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for (int i = methodArgs.length - 1; i < classes.length; ++i) {
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if (!isConvertible(vararg, classes[i], false)) {
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private static boolean isConvertible(Class formal, Class actual,
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boolean possibleVarArg) {
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return IntrospectionUtils.
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isMethodInvocationConvertible(formal, actual, possibleVarArg);
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private static boolean isStrictConvertible(Class formal, Class actual,
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boolean possibleVarArg) {
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return IntrospectionUtils.
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isStrictMethodInvocationConvertible(formal, actual, possibleVarArg);
added
removed
src/java/org/apache/commons/jexl/util/introspection/MethodMap.java
