| /* |
| * 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.logging.log4j.core.util; |
| |
| import java.lang.reflect.AccessibleObject; |
| import java.lang.reflect.Constructor; |
| import java.lang.reflect.Field; |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.Member; |
| import java.lang.reflect.Modifier; |
| import java.util.Objects; |
| |
| /** |
| * Utility class for performing common reflective operations. |
| * |
| * @since 2.1 |
| */ |
| public final class ReflectionUtil { |
| private ReflectionUtil() { |
| } |
| |
| /** |
| * Indicates whether or not a {@link Member} is both public and is contained in a public class. |
| * |
| * @param <T> type of the object whose accessibility to test |
| * @param member the Member to check for public accessibility (must not be {@code null}). |
| * @return {@code true} if {@code member} is public and contained in a public class. |
| * @throws NullPointerException if {@code member} is {@code null}. |
| */ |
| public static <T extends AccessibleObject & Member> boolean isAccessible(final T member) { |
| Objects.requireNonNull(member, "No member provided"); |
| return Modifier.isPublic(member.getModifiers()) && Modifier.isPublic(member.getDeclaringClass().getModifiers()); |
| } |
| |
| /** |
| * Makes a {@link Member} {@link AccessibleObject#isAccessible() accessible} if the member is not public. |
| * |
| * @param <T> type of the object to make accessible |
| * @param member the Member to make accessible (must not be {@code null}). |
| * @throws NullPointerException if {@code member} is {@code null}. |
| */ |
| public static <T extends AccessibleObject & Member> void makeAccessible(final T member) { |
| if (!isAccessible(member) && !member.isAccessible()) { |
| member.setAccessible(true); |
| } |
| } |
| |
| /** |
| * Makes a {@link Field} {@link AccessibleObject#isAccessible() accessible} if it is not public or if it is final. |
| * |
| * <p>Note that using this method to make a {@code final} field writable will most likely not work very well due to |
| * compiler optimizations and the like.</p> |
| * |
| * @param field the Field to make accessible (must not be {@code null}). |
| * @throws NullPointerException if {@code field} is {@code null}. |
| */ |
| public static void makeAccessible(final Field field) { |
| Objects.requireNonNull(field, "No field provided"); |
| if ((!isAccessible(field) || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) { |
| field.setAccessible(true); |
| } |
| } |
| |
| /** |
| * Gets the value of a {@link Field}, making it accessible if required. |
| * |
| * @param field the Field to obtain a value from (must not be {@code null}). |
| * @param instance the instance to obtain the field value from or {@code null} only if the field is static. |
| * @return the value stored by the field. |
| * @throws NullPointerException if {@code field} is {@code null}, or if {@code instance} is {@code null} but |
| * {@code field} is not {@code static}. |
| * @see Field#get(Object) |
| */ |
| public static Object getFieldValue(final Field field, final Object instance) { |
| makeAccessible(field); |
| if (!Modifier.isStatic(field.getModifiers())) { |
| Objects.requireNonNull(instance, "No instance given for non-static field"); |
| } |
| try { |
| return field.get(instance); |
| } catch (final IllegalAccessException e) { |
| throw new UnsupportedOperationException(e); |
| } |
| } |
| |
| /** |
| * Gets the value of a static {@link Field}, making it accessible if required. |
| * |
| * @param field the Field to obtain a value from (must not be {@code null}). |
| * @return the value stored by the static field. |
| * @throws NullPointerException if {@code field} is {@code null}, or if {@code field} is not {@code static}. |
| * @see Field#get(Object) |
| */ |
| public static Object getStaticFieldValue(final Field field) { |
| return getFieldValue(field, null); |
| } |
| |
| /** |
| * Sets the value of a {@link Field}, making it accessible if required. |
| * |
| * @param field the Field to write a value to (must not be {@code null}). |
| * @param instance the instance to write the value to or {@code null} only if the field is static. |
| * @param value the (possibly wrapped) value to write to the field. |
| * @throws NullPointerException if {@code field} is {@code null}, or if {@code instance} is {@code null} but |
| * {@code field} is not {@code static}. |
| * @see Field#set(Object, Object) |
| */ |
| public static void setFieldValue(final Field field, final Object instance, final Object value) { |
| makeAccessible(field); |
| if (!Modifier.isStatic(field.getModifiers())) { |
| Objects.requireNonNull(instance, "No instance given for non-static field"); |
| } |
| try { |
| field.set(instance, value); |
| } catch (final IllegalAccessException e) { |
| throw new UnsupportedOperationException(e); |
| } |
| } |
| |
| /** |
| * Sets the value of a static {@link Field}, making it accessible if required. |
| * |
| * @param field the Field to write a value to (must not be {@code null}). |
| * @param value the (possibly wrapped) value to write to the field. |
| * @throws NullPointerException if {@code field} is {@code null}, or if {@code field} is not {@code static}. |
| * @see Field#set(Object, Object) |
| */ |
| public static void setStaticFieldValue(final Field field, final Object value) { |
| setFieldValue(field, null, value); |
| } |
| |
| /** |
| * Gets the default (no-arg) constructor for a given class. |
| * |
| * @param clazz the class to find a constructor for |
| * @param <T> the type made by the constructor |
| * @return the default constructor for the given class |
| * @throws IllegalStateException if no default constructor can be found |
| */ |
| public static <T> Constructor<T> getDefaultConstructor(final Class<T> clazz) { |
| Objects.requireNonNull(clazz, "No class provided"); |
| try { |
| final Constructor<T> constructor = clazz.getDeclaredConstructor(); |
| makeAccessible(constructor); |
| return constructor; |
| } catch (final NoSuchMethodException ignored) { |
| try { |
| final Constructor<T> constructor = clazz.getConstructor(); |
| makeAccessible(constructor); |
| return constructor; |
| } catch (final NoSuchMethodException e) { |
| throw new IllegalStateException(e); |
| } |
| } |
| } |
| |
| /** |
| * Constructs a new {@code T} object using the default constructor of its class. Any exceptions thrown by the |
| * constructor will be rethrown by this method, possibly wrapped in an |
| * {@link java.lang.reflect.UndeclaredThrowableException}. |
| * |
| * @param clazz the class to use for instantiation. |
| * @param <T> the type of the object to construct. |
| * @return a new instance of T made from its default constructor. |
| * @throws IllegalArgumentException if the given class is abstract, an interface, an array class, a primitive type, |
| * or void |
| * @throws IllegalStateException if access is denied to the constructor, or there are no default constructors |
| */ |
| public static <T> T instantiate(final Class<T> clazz) { |
| Objects.requireNonNull(clazz, "No class provided"); |
| final Constructor<T> constructor = getDefaultConstructor(clazz); |
| try { |
| return constructor.newInstance(); |
| } catch (final LinkageError | InstantiationException e) { |
| // LOG4J2-1051 |
| // On platforms like Google App Engine and Android, some JRE classes are not supported: JMX, JNDI, etc. |
| throw new IllegalArgumentException(e); |
| } catch (final IllegalAccessException e) { |
| throw new IllegalStateException(e); |
| } catch (final InvocationTargetException e) { |
| Throwables.rethrow(e.getCause()); |
| throw new InternalError("Unreachable"); |
| } |
| } |
| } |