org.apache.maven.model.interpolation.reflection.MethodMap Maven / Gradle / Ivy
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/*
* 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.
*/
package org.apache.maven.model.interpolation.reflection;
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;
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 final long serialVersionUID = 751688436639650618L;
}
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;
default:
}
}
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;
}
}