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/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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.springframework.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.UndeclaredThrowableException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.springframework.lang.Nullable;

/**
 * Simple utility class for working with the reflection API and handling reflection exceptions.
 *
 * 

* Only intended for internal use. * * @author Juergen Hoeller * @author Rob Harrop * @author Rod Johnson * @author Costin Leau * @author Sam Brannen * @author Chris Beams * @since 1.2.2 */ public abstract class ReflectionUtils { private static final Method[] NO_METHODS = {}; /** * Cache for {@link Class#getDeclaredMethods()} plus equivalent default methods from Java 8 based * interfaces, allowing for fast iteration. */ private static final Map, Method[]> declaredMethodsCache = new ConcurrentReferenceHashMap<>(256); /** * Attempt to find a {@link Method} on the supplied class with the supplied name and no * parameters. Searches all superclasses up to {@code Object}. *

* Returns {@code null} if no {@link Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @return the Method object, or {@code null} if none found */ @Nullable public static Method findMethod(Class clazz, String name) { return findMethod(clazz, name, new Class[0]); } /** * Attempt to find a {@link Method} on the supplied class with the supplied name and parameter * types. Searches all superclasses up to {@code Object}. *

* Returns {@code null} if no {@link Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @param paramTypes the parameter types of the method (may be {@code null} to indicate any * signature) * @return the Method object, or {@code null} if none found */ @Nullable public static Method findMethod(Class clazz, String name, @Nullable Class... paramTypes) { Assert.notNull(clazz, "Class must not be null"); Assert.notNull(name, "Method name must not be null"); Class searchType = clazz; while (searchType != null) { Method[] methods = (searchType.isInterface() ? searchType.getMethods() : getDeclaredMethods(searchType)); for (Method method : methods) { if (name.equals(method.getName()) && (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes()))) { return method; } } searchType = searchType.getSuperclass(); } return null; } /** * Invoke the specified {@link Method} against the supplied target object with no arguments. The * target object can be {@code null} when invoking a static {@link Method}. *

* Thrown exceptions are handled via a call to {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @return the invocation result, if any * @see #invokeMethod(java.lang.reflect.Method, Object, Object[]) */ @Nullable public static Object invokeMethod(Method method, @Nullable Object target) { return invokeMethod(method, target, new Object[0]); } /** * Invoke the specified {@link Method} against the supplied target object with the supplied * arguments. The target object can be {@code null} when invoking a static {@link Method}. *

* Thrown exceptions are handled via a call to {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @param args the invocation arguments (may be {@code null}) * @return the invocation result, if any */ @Nullable public static Object invokeMethod(Method method, @Nullable Object target, @Nullable Object... args) { try { return method.invoke(target, args); } catch (Exception ex) { handleReflectionException(ex); } throw new IllegalStateException("Should never get here"); } /** * Handle the given reflection exception. Should only be called if no checked exception is * expected to be thrown by the target method. *

* Throws the underlying RuntimeException or Error in case of an InvocationTargetException with * such a root cause. Throws an IllegalStateException with an appropriate message or * UndeclaredThrowableException otherwise. * * @param ex the reflection exception to handle */ public static void handleReflectionException(Exception ex) { if (ex instanceof NoSuchMethodException) { throw new IllegalStateException("Method not found: " + ex.getMessage()); } if (ex instanceof IllegalAccessException) { throw new IllegalStateException("Could not access method: " + ex.getMessage()); } if (ex instanceof InvocationTargetException) { handleInvocationTargetException((InvocationTargetException) ex); } if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } throw new UndeclaredThrowableException(ex); } /** * Handle the given invocation target exception. Should only be called if no checked exception is * expected to be thrown by the target method. *

* Throws the underlying RuntimeException or Error in case of such a root cause. Throws an * UndeclaredThrowableException otherwise. * * @param ex the invocation target exception to handle */ public static void handleInvocationTargetException(InvocationTargetException ex) { rethrowRuntimeException(ex.getTargetException()); } /** * Rethrow the given {@link Throwable exception}, which is presumably the target * exception of an {@link InvocationTargetException}. Should only be called if no checked * exception is expected to be thrown by the target method. *

* Rethrows the underlying exception cast to a {@link RuntimeException} or {@link Error} if * appropriate; otherwise, throws an {@link UndeclaredThrowableException}. * * @param ex the exception to rethrow * @throws RuntimeException the rethrown exception */ public static void rethrowRuntimeException(Throwable ex) { if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } if (ex instanceof Error) { throw (Error) ex; } throw new UndeclaredThrowableException(ex); } /** * Determine whether the given method is a "hashCode" method. * * @see java.lang.Object#hashCode() */ public static boolean isHashCodeMethod(@Nullable Method method) { return (method != null && method.getName().equals("hashCode") && method.getParameterCount() == 0); } /** * Determine whether the given method is a "toString" method. * * @see java.lang.Object#toString() */ public static boolean isToStringMethod(@Nullable Method method) { return (method != null && method.getName().equals("toString") && method.getParameterCount() == 0); } /** * Perform the given callback operation on all matching methods of the given class and * superclasses. *

* The same named method occurring on subclass and superclass will appear twice, unless excluded * by a {@link MethodFilter}. * * @param clazz the class to introspect * @param mc the callback to invoke for each method * @throws IllegalStateException if introspection fails * @see #doWithMethods(Class, MethodCallback, MethodFilter) */ public static void doWithMethods(Class clazz, MethodCallback mc) { doWithMethods(clazz, mc, null); } /** * Perform the given callback operation on all matching methods of the given class and * superclasses (or given interface and super-interfaces). *

* The same named method occurring on subclass and superclass will appear twice, unless excluded * by the specified {@link MethodFilter}. * * @param clazz the class to introspect * @param mc the callback to invoke for each method * @param mf the filter that determines the methods to apply the callback to * @throws IllegalStateException if introspection fails */ public static void doWithMethods(Class clazz, MethodCallback mc, @Nullable MethodFilter mf) { // Keep backing up the inheritance hierarchy. Method[] methods = getDeclaredMethods(clazz); for (Method method : methods) { if (mf != null && !mf.matches(method)) { continue; } try { mc.doWith(method); } catch (IllegalAccessException ex) { throw new IllegalStateException("Not allowed to access method '" + method.getName() + "': " + ex); } } if (clazz.getSuperclass() != null) { doWithMethods(clazz.getSuperclass(), mc, mf); } else if (clazz.isInterface()) { for (Class superIfc : clazz.getInterfaces()) { doWithMethods(superIfc, mc, mf); } } } /** * Get all declared methods on the leaf class and all superclasses. Leaf class methods are * included first. * * @param leafClass the class to introspect * @throws IllegalStateException if introspection fails */ public static Method[] getAllDeclaredMethods(Class leafClass) { final List methods = new ArrayList<>(32); doWithMethods(leafClass, methods::add); return methods.toArray(new Method[0]); } /** * This variant retrieves {@link Class#getDeclaredMethods()} from a local cache in order to avoid * the JVM's SecurityManager check and defensive array copying. In addition, it also includes Java * 8 default methods from locally implemented interfaces, since those are effectively to be * treated just like declared methods. * * @param clazz the class to introspect * @return the cached array of methods * @throws IllegalStateException if introspection fails * @see Class#getDeclaredMethods() */ private static Method[] getDeclaredMethods(Class clazz) { Assert.notNull(clazz, "Class must not be null"); Method[] result = declaredMethodsCache.get(clazz); if (result == null) { try { Method[] declaredMethods = clazz.getDeclaredMethods(); List defaultMethods = findConcreteMethodsOnInterfaces(clazz); if (defaultMethods != null) { result = new Method[declaredMethods.length + defaultMethods.size()]; System.arraycopy(declaredMethods, 0, result, 0, declaredMethods.length); int index = declaredMethods.length; for (Method defaultMethod : defaultMethods) { result[index] = defaultMethod; index++; } } else { result = declaredMethods; } declaredMethodsCache.put(clazz, (result.length == 0 ? NO_METHODS : result)); } catch (Throwable ex) { throw new IllegalStateException("Failed to introspect Class [" + clazz.getName() + "] from ClassLoader [" + clazz.getClassLoader() + "]", ex); } } return result; } @Nullable private static List findConcreteMethodsOnInterfaces(Class clazz) { List result = null; for (Class ifc : clazz.getInterfaces()) { for (Method ifcMethod : ifc.getMethods()) { if (!Modifier.isAbstract(ifcMethod.getModifiers())) { if (result == null) { result = new LinkedList<>(); } result.add(ifcMethod); } } } return result; } /** * Action to take on each method. */ @FunctionalInterface public interface MethodCallback { /** * Perform an operation using the given method. * * @param method the method to operate on */ void doWith(Method method) throws IllegalArgumentException, IllegalAccessException; } /** * Callback optionally used to filter methods to be operated on by a method callback. */ @FunctionalInterface public interface MethodFilter { /** * Determine whether the given method matches. * * @param method the method to check */ boolean matches(Method method); } /** * Make the given method accessible, explicitly setting it accessible if necessary. The * {@code setAccessible(true)} method is only called when actually necessary, to avoid unnecessary * conflicts with a JVM SecurityManager (if active). * * @param method the method to make accessible * @see java.lang.reflect.Method#setAccessible */ public static void makeAccessible(Method method) { if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) && !method.isAccessible()) { method.setAccessible(true); } } /** * Determine whether the given method is an "equals" method. * * @see java.lang.Object#equals(Object) */ public static boolean isEqualsMethod(@Nullable Method method) { if (method == null || !method.getName().equals("equals")) { return false; } Class[] paramTypes = method.getParameterTypes(); return (paramTypes.length == 1 && paramTypes[0] == Object.class); } /****************************** For Test ****************************/ }





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