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Apache Commons Lang, a package of Java utility classes for the
classes that are in java.lang's hierarchy, or are considered to be so
standard as to justify existence in java.lang.
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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.commons.lang3.reflect;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Constructor;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import org.apache.commons.lang3.ClassUtils;
/**
* Contains common code for working with {@link java.lang.reflect.Method Methods}/{@link java.lang.reflect.Constructor Constructors},
* extracted and refactored from {@link MethodUtils} when it was imported from Commons BeanUtils.
*
* @since 2.5
*/
abstract class MemberUtils {
// TODO extract an interface to implement compareParameterSets(...)?
private static final int ACCESS_TEST = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE;
/** Array of primitive number types ordered by "promotability" */
private static final Class[] ORDERED_PRIMITIVE_TYPES = { Byte.TYPE, Short.TYPE,
Character.TYPE, Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE };
/**
* XXX Default access superclass workaround.
*
* When a {@code public} class has a default access superclass with {@code public} members,
* these members are accessible. Calling them from compiled code works fine.
* Unfortunately, on some JVMs, using reflection to invoke these members
* seems to (wrongly) prevent access even when the modifier is {@code public}.
* Calling {@code setAccessible(true)} solves the problem but will only work from
* sufficiently privileged code. Better workarounds would be gratefully
* accepted.
* @param o the AccessibleObject to set as accessible
* @return a boolean indicating whether the accessibility of the object was set to true.
*/
static boolean setAccessibleWorkaround(final AccessibleObject o) {
if (o == null || o.isAccessible()) {
return false;
}
final Member m = (Member) o;
if (!o.isAccessible() && Modifier.isPublic(m.getModifiers()) && isPackageAccess(m.getDeclaringClass().getModifiers())) {
try {
o.setAccessible(true);
return true;
} catch (final SecurityException e) { // NOPMD
// ignore in favor of subsequent IllegalAccessException
}
}
return false;
}
/**
* Returns whether a given set of modifiers implies package access.
* @param modifiers to test
* @return {@code true} unless {@code package}/{@code protected}/{@code private} modifier detected
*/
static boolean isPackageAccess(final int modifiers) {
return (modifiers & ACCESS_TEST) == 0;
}
/**
* Returns whether a {@link Member} is accessible.
* @param m Member to check
* @return {@code true} if m is accessible
*/
static boolean isAccessible(final Member m) {
return m != null && Modifier.isPublic(m.getModifiers()) && !m.isSynthetic();
}
/**
* Compares the relative fitness of two Constructors in terms of how well they
* match a set of runtime parameter types, such that a list ordered
* by the results of the comparison would return the best match first
* (least).
*
* @param left the "left" Constructor
* @param right the "right" Constructor
* @param actual the runtime parameter types to match against
* {@code left}/{@code right}
* @return int consistent with {@code compare} semantics
* @since 3.5
*/
static int compareConstructorFit(final Constructor left, final Constructor right, final Class[] actual) {
return compareParameterTypes(Executable.of(left), Executable.of(right), actual);
}
/**
* Compares the relative fitness of two Methods in terms of how well they
* match a set of runtime parameter types, such that a list ordered
* by the results of the comparison would return the best match first
* (least).
*
* @param left the "left" Method
* @param right the "right" Method
* @param actual the runtime parameter types to match against
* {@code left}/{@code right}
* @return int consistent with {@code compare} semantics
* @since 3.5
*/
static int compareMethodFit(final Method left, final Method right, final Class[] actual) {
return compareParameterTypes(Executable.of(left), Executable.of(right), actual);
}
/**
* Compares the relative fitness of two Executables in terms of how well they
* match a set of runtime parameter types, such that a list ordered
* by the results of the comparison would return the best match first
* (least).
*
* @param left the "left" Executable
* @param right the "right" Executable
* @param actual the runtime parameter types to match against
* {@code left}/{@code right}
* @return int consistent with {@code compare} semantics
*/
private static int compareParameterTypes(final Executable left, final Executable right, final Class[] actual) {
final float leftCost = getTotalTransformationCost(actual, left);
final float rightCost = getTotalTransformationCost(actual, right);
return Float.compare(leftCost, rightCost);
}
/**
* Returns the sum of the object transformation cost for each class in the
* source argument list.
* @param srcArgs The source arguments
* @param executable The executable to calculate transformation costs for
* @return The total transformation cost
*/
private static float getTotalTransformationCost(final Class[] srcArgs, final Executable executable) {
final Class[] destArgs = executable.getParameterTypes();
final boolean isVarArgs = executable.isVarArgs();
// "source" and "destination" are the actual and declared args respectively.
float totalCost = 0.0f;
final long normalArgsLen = isVarArgs ? destArgs.length-1 : destArgs.length;
if (srcArgs.length < normalArgsLen) {
return Float.MAX_VALUE;
}
for (int i = 0; i < normalArgsLen; i++) {
totalCost += getObjectTransformationCost(srcArgs[i], destArgs[i]);
}
if (isVarArgs) {
// When isVarArgs is true, srcArgs and dstArgs may differ in length.
// There are two special cases to consider:
final boolean noVarArgsPassed = srcArgs.length < destArgs.length;
final boolean explicitArrayForVarags = srcArgs.length == destArgs.length && srcArgs[srcArgs.length-1].isArray();
final float varArgsCost = 0.001f;
final Class destClass = destArgs[destArgs.length-1].getComponentType();
if (noVarArgsPassed) {
// When no varargs passed, the best match is the most generic matching type, not the most specific.
totalCost += getObjectTransformationCost(destClass, Object.class) + varArgsCost;
} else if (explicitArrayForVarags) {
final Class sourceClass = srcArgs[srcArgs.length-1].getComponentType();
totalCost += getObjectTransformationCost(sourceClass, destClass) + varArgsCost;
} else {
// This is typical varargs case.
for (int i = destArgs.length-1; i < srcArgs.length; i++) {
final Class srcClass = srcArgs[i];
totalCost += getObjectTransformationCost(srcClass, destClass) + varArgsCost;
}
}
}
return totalCost;
}
/**
* Gets the number of steps required needed to turn the source class into
* the destination class. This represents the number of steps in the object
* hierarchy graph.
* @param srcClass The source class
* @param destClass The destination class
* @return The cost of transforming an object
*/
private static float getObjectTransformationCost(Class srcClass, final Class destClass) {
if (destClass.isPrimitive()) {
return getPrimitivePromotionCost(srcClass, destClass);
}
float cost = 0.0f;
while (srcClass != null && !destClass.equals(srcClass)) {
if (destClass.isInterface() && ClassUtils.isAssignable(srcClass, destClass)) {
// slight penalty for interface match.
// we still want an exact match to override an interface match,
// but
// an interface match should override anything where we have to
// get a superclass.
cost += 0.25f;
break;
}
cost++;
srcClass = srcClass.getSuperclass();
}
/*
* If the destination class is null, we've traveled all the way up to
* an Object match. We'll penalize this by adding 1.5 to the cost.
*/
if (srcClass == null) {
cost += 1.5f;
}
return cost;
}
/**
* Gets the number of steps required to promote a primitive number to another
* type.
* @param srcClass the (primitive) source class
* @param destClass the (primitive) destination class
* @return The cost of promoting the primitive
*/
private static float getPrimitivePromotionCost(final Class srcClass, final Class destClass) {
float cost = 0.0f;
Class cls = srcClass;
if (!cls.isPrimitive()) {
// slight unwrapping penalty
cost += 0.1f;
cls = ClassUtils.wrapperToPrimitive(cls);
}
for (int i = 0; cls != destClass && i < ORDERED_PRIMITIVE_TYPES.length; i++) {
if (cls == ORDERED_PRIMITIVE_TYPES[i]) {
cost += 0.1f;
if (i < ORDERED_PRIMITIVE_TYPES.length - 1) {
cls = ORDERED_PRIMITIVE_TYPES[i + 1];
}
}
}
return cost;
}
static boolean isMatchingMethod(final Method method, final Class[] parameterTypes) {
return isMatchingExecutable(Executable.of(method), parameterTypes);
}
static boolean isMatchingConstructor(final Constructor method, final Class[] parameterTypes) {
return isMatchingExecutable(Executable.of(method), parameterTypes);
}
private static boolean isMatchingExecutable(final Executable method, final Class[] parameterTypes) {
final Class[] methodParameterTypes = method.getParameterTypes();
if (ClassUtils.isAssignable(parameterTypes, methodParameterTypes, true)) {
return true;
}
if (method.isVarArgs()) {
int i;
for (i = 0; i < methodParameterTypes.length - 1 && i < parameterTypes.length; i++) {
if (!ClassUtils.isAssignable(parameterTypes[i], methodParameterTypes[i], true)) {
return false;
}
}
final Class varArgParameterType = methodParameterTypes[methodParameterTypes.length - 1].getComponentType();
for (; i < parameterTypes.length; i++) {
if (!ClassUtils.isAssignable(parameterTypes[i], varArgParameterType, true)) {
return false;
}
}
return true;
}
return false;
}
/**
* A class providing a subset of the API of java.lang.reflect.Executable in Java 1.8,
* providing a common representation for function signatures for Constructors and Methods.
*/
private static final class Executable {
private final Class[] parameterTypes;
private final boolean isVarArgs;
private static Executable of(final Method method) {
return new Executable(method);
}
private static Executable of(final Constructor constructor) {
return new Executable(constructor);
}
private Executable(final Method method) {
parameterTypes = method.getParameterTypes();
isVarArgs = method.isVarArgs();
}
private Executable(final Constructor constructor) {
parameterTypes = constructor.getParameterTypes();
isVarArgs = constructor.isVarArgs();
}
public Class[] getParameterTypes() {
return parameterTypes;
}
public boolean isVarArgs() {
return isVarArgs;
}
}
}