1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17
18 package org.apache.logging.log4j.core.util;
19
20 import java.lang.reflect.AccessibleObject;
21 import java.lang.reflect.Constructor;
22 import java.lang.reflect.Field;
23 import java.lang.reflect.InvocationTargetException;
24 import java.lang.reflect.Member;
25 import java.lang.reflect.Modifier;
26 import java.util.Objects;
27
28 /**
29 * Utility class for performing common reflective operations.
30 *
31 * @since 2.1
32 */
33 public final class ReflectionUtil {
34 private ReflectionUtil() {
35 }
36
37 /**
38 * Indicates whether or not a {@link Member} is both public and is contained in a public class.
39 *
40 * @param <T> type of the object whose accessibility to test
41 * @param member the Member to check for public accessibility (must not be {@code null}).
42 * @return {@code true} if {@code member} is public and contained in a public class.
43 * @throws NullPointerException if {@code member} is {@code null}.
44 */
45 public static <T extends AccessibleObject & Member> boolean isAccessible(final T member) {
46 Objects.requireNonNull(member, "No member provided");
47 return Modifier.isPublic(member.getModifiers()) && Modifier.isPublic(member.getDeclaringClass().getModifiers());
48 }
49
50 /**
51 * Makes a {@link Member} {@link AccessibleObject#isAccessible() accessible} if the member is not public.
52 *
53 * @param <T> type of the object to make accessible
54 * @param member the Member to make accessible (must not be {@code null}).
55 * @throws NullPointerException if {@code member} is {@code null}.
56 */
57 public static <T extends AccessibleObject & Member> void makeAccessible(final T member) {
58 if (!isAccessible(member) && !member.isAccessible()) {
59 member.setAccessible(true);
60 }
61 }
62
63 /**
64 * Makes a {@link Field} {@link AccessibleObject#isAccessible() accessible} if it is not public or if it is final.
65 *
66 * <p>Note that using this method to make a {@code final} field writable will most likely not work very well due to
67 * compiler optimizations and the like.</p>
68 *
69 * @param field the Field to make accessible (must not be {@code null}).
70 * @throws NullPointerException if {@code field} is {@code null}.
71 */
72 public static void makeAccessible(final Field field) {
73 Objects.requireNonNull(field, "No field provided");
74 if ((!isAccessible(field) || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) {
75 field.setAccessible(true);
76 }
77 }
78
79 /**
80 * Gets the value of a {@link Field}, making it accessible if required.
81 *
82 * @param field the Field to obtain a value from (must not be {@code null}).
83 * @param instance the instance to obtain the field value from or {@code null} only if the field is static.
84 * @return the value stored by the field.
85 * @throws NullPointerException if {@code field} is {@code null}, or if {@code instance} is {@code null} but
86 * {@code field} is not {@code static}.
87 * @see Field#get(Object)
88 */
89 public static Object getFieldValue(final Field field, final Object instance) {
90 makeAccessible(field);
91 if (!Modifier.isStatic(field.getModifiers())) {
92 Objects.requireNonNull(instance, "No instance given for non-static field");
93 }
94 try {
95 return field.get(instance);
96 } catch (final IllegalAccessException e) {
97 throw new UnsupportedOperationException(e);
98 }
99 }
100
101 /**
102 * Gets the value of a static {@link Field}, making it accessible if required.
103 *
104 * @param field the Field to obtain a value from (must not be {@code null}).
105 * @return the value stored by the static field.
106 * @throws NullPointerException if {@code field} is {@code null}, or if {@code field} is not {@code static}.
107 * @see Field#get(Object)
108 */
109 public static Object getStaticFieldValue(final Field field) {
110 return getFieldValue(field, null);
111 }
112
113 /**
114 * Sets the value of a {@link Field}, making it accessible if required.
115 *
116 * @param field the Field to write a value to (must not be {@code null}).
117 * @param instance the instance to write the value to or {@code null} only if the field is static.
118 * @param value the (possibly wrapped) value to write to the field.
119 * @throws NullPointerException if {@code field} is {@code null}, or if {@code instance} is {@code null} but
120 * {@code field} is not {@code static}.
121 * @see Field#set(Object, Object)
122 */
123 public static void setFieldValue(final Field field, final Object instance, final Object value) {
124 makeAccessible(field);
125 if (!Modifier.isStatic(field.getModifiers())) {
126 Objects.requireNonNull(instance, "No instance given for non-static field");
127 }
128 try {
129 field.set(instance, value);
130 } catch (final IllegalAccessException e) {
131 throw new UnsupportedOperationException(e);
132 }
133 }
134
135 /**
136 * Sets the value of a static {@link Field}, making it accessible if required.
137 *
138 * @param field the Field to write a value to (must not be {@code null}).
139 * @param value the (possibly wrapped) value to write to the field.
140 * @throws NullPointerException if {@code field} is {@code null}, or if {@code field} is not {@code static}.
141 * @see Field#set(Object, Object)
142 */
143 public static void setStaticFieldValue(final Field field, final Object value) {
144 setFieldValue(field, null, value);
145 }
146
147 /**
148 * Gets the default (no-arg) constructor for a given class.
149 *
150 * @param clazz the class to find a constructor for
151 * @param <T> the type made by the constructor
152 * @return the default constructor for the given class
153 * @throws IllegalStateException if no default constructor can be found
154 */
155 public static <T> Constructor<T> getDefaultConstructor(final Class<T> clazz) {
156 Objects.requireNonNull(clazz, "No class provided");
157 try {
158 final Constructor<T> constructor = clazz.getDeclaredConstructor();
159 makeAccessible(constructor);
160 return constructor;
161 } catch (final NoSuchMethodException ignored) {
162 try {
163 final Constructor<T> constructor = clazz.getConstructor();
164 makeAccessible(constructor);
165 return constructor;
166 } catch (final NoSuchMethodException e) {
167 throw new IllegalStateException(e);
168 }
169 }
170 }
171
172 /**
173 * Constructs a new {@code T} object using the default constructor of its class. Any exceptions thrown by the
174 * constructor will be rethrown by this method, possibly wrapped in an
175 * {@link java.lang.reflect.UndeclaredThrowableException}.
176 *
177 * @param clazz the class to use for instantiation.
178 * @param <T> the type of the object to construct.
179 * @return a new instance of T made from its default constructor.
180 * @throws IllegalArgumentException if the given class is abstract, an interface, an array class, a primitive type,
181 * or void
182 * @throws IllegalStateException if access is denied to the constructor, or there are no default constructors
183 */
184 public static <T> T instantiate(final Class<T> clazz) {
185 Objects.requireNonNull(clazz, "No class provided");
186 final Constructor<T> constructor = getDefaultConstructor(clazz);
187 try {
188 return constructor.newInstance();
189 } catch (final LinkageError | InstantiationException e) {
190 // LOG4J2-1051
191 // On platforms like Google App Engine and Android, some JRE classes are not supported: JMX, JNDI, etc.
192 throw new IllegalArgumentException(e);
193 } catch (final IllegalAccessException e) {
194 throw new IllegalStateException(e);
195 } catch (final InvocationTargetException e) {
196 Throwables.rethrow(e.getCause());
197 throw new InternalError("Unreachable");
198 }
199 }
200 }