ReflectionUtils.java
/*
* Copyright (C) 2015 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.codehaus.gmavenplus.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Inspired heavily by Spring's <a href="https://github.com/SpringSource/spring-framework/blob/master/spring-core/src/main/java/org/springframework/util/ReflectionUtils.java">ReflectionUtils</a>.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @author Rod Johnson
* @author Costin Leau
* @author Sam Brannen
* @author Chris Beams
* @author Keegan Witt
* @since 1.0-beta-1
*/
public class ReflectionUtils {
private ReflectionUtils() {
}
/**
* Attempt to find a {@link Constructor} on the supplied class with the supplied parameter types.
* Searches all superclasses up to <code>Object</code>.
*
* @param clazz The class to introspect
* @param paramTypes The parameter types of the method (may be <code>null</code> to indicate any signature)
* @return The Constructor object
*/
public static Constructor<?> findConstructor(final Class<?> clazz, final Class<?>... paramTypes) {
if (clazz == null) {
throw new IllegalArgumentException("Class must not be null.");
}
Class<?> searchType = clazz;
while (searchType != null) {
Constructor<?>[] constructors = searchType.isInterface() ? clazz.getConstructors() : clazz.getDeclaredConstructors();
for (Constructor<?> constructor : constructors) {
if (paramTypes == null || Arrays.equals(paramTypes, constructor.getParameterTypes())) {
return constructor;
}
}
searchType = searchType.getSuperclass();
}
throw new IllegalArgumentException("Unable to find constructor " + clazz.getName() + "(" + Arrays.toString(paramTypes).replaceAll("^\\[", "").replaceAll("]$", "").replaceAll("class ", "") + ").");
}
/**
* Attempt to find a {@link Field field} on the supplied {@link Class} with the supplied <code>name</code> and/or {@link Class type}.
* Searches all superclasses up to {@link Object}.
*
* @param clazz The class to introspect
* @param name The name of the field (may be <code>null</code> if type is specified)
* @param type The type of the field (may be <code>null</code> if name is specified)
* @return The corresponding Field object
*/
public static Field findField(final Class<?> clazz, final String name, final Class<?> type) {
if (clazz == null) {
throw new IllegalArgumentException("Class must not be null");
}
if (name == null && type == null) {
throw new IllegalArgumentException("Either name or type of the field must be specified.");
}
Class<?> searchType = clazz;
while (Object.class != searchType && searchType != null) {
Field[] fields = searchType.getDeclaredFields();
for (Field field : fields) {
if ((name == null || name.equals(field.getName())) && (type == null || type.equals(field.getType()))) {
return field;
}
}
searchType = searchType.getSuperclass();
}
throw new IllegalArgumentException("Unable to find " + (type != null ? type.getName() : "") + " " + (name != null ? name : "") + ".");
}
/**
* Attempt to find a {@link Method} on the supplied class with the supplied name and parameter types.
* Searches all superclasses up to <code>Object</code>.
*
* @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</code> to indicate any signature)
* @return The Method object
*/
public static Method findMethod(final Class<?> clazz, final String name, final Class<?>... paramTypes) {
if (clazz == null) {
throw new IllegalArgumentException("Class must not be null.");
}
if (name == null) {
throw new IllegalArgumentException("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();
}
throw new IllegalArgumentException("Unable to find method " + clazz.getName() + "." + name + "(" + Arrays.toString(paramTypes).replaceAll("^\\[", "").replaceAll("]$", "").replaceAll("class ", "") + ").");
}
/**
* Find and return the specified value from the specified enum class.
*
* @param clazz The enum class to introspect
* @param valueName The name of the enum value to get
* @return The enum value
*/
public static Object getEnumValue(final Class<?> clazz, final String valueName) {
if (clazz.isEnum()) {
for (Object o : clazz.getEnumConstants()) {
if (o.toString().equals(valueName)) {
return o;
}
}
throw new IllegalArgumentException("Unable to get an enum constant with that name.");
} else {
throw new IllegalArgumentException(clazz + " must be an enum.");
}
}
/**
* Get the field represented by the supplied {@link Field field object} on the specified {@link Object target object}.
* In accordance with {@link Field#get(Object)} semantics, the returned value is automatically wrapped if the underlying field has a primitive type.
*
* @param field The field to get
* @param target The target object from which to get the field
* @return The field's current value
* @throws IllegalAccessException when unable to access the specified field because access modifiers prevent it
*/
public static Object getField(final Field field, final Object target) throws IllegalAccessException {
field.setAccessible(true);
return field.get(target);
}
/**
* Get the field represented by the supplied {@link Field field object} on the specified {@link Object target object}.
* In accordance with {@link Field#get(Object)} semantics, the returned value is automatically wrapped if the underlying field has a primitive type.
*
* @param field The field to get
* @return The field's current value
* @throws IllegalAccessException when unable to access the specified field because access modifiers prevent it
*/
public static Object getStaticField(final Field field) throws IllegalAccessException {
if (!Modifier.isStatic(field.getModifiers())) {
throw new IllegalArgumentException("Field must be static.");
}
return getField(field, null);
}
/**
* Invoke the specified {@link Constructor} with the supplied arguments.
*
* @param constructor The method to invoke
* @param args The invocation arguments (may be <code>null</code>)
* @return The invocation result, if any
* @throws IllegalAccessException when unable to access the specified constructor because access modifiers prevent it
* @throws java.lang.reflect.InvocationTargetException when a reflection invocation fails
* @throws InstantiationException when an instantiation fails
*/
public static Object invokeConstructor(final Constructor<?> constructor, final Object... args) throws InvocationTargetException, IllegalAccessException, InstantiationException {
if (constructor == null) {
throw new IllegalArgumentException("Constructor must not be null.");
}
constructor.setAccessible(true);
return constructor.newInstance(args);
}
/**
* Invoke the specified {@link Method} against the supplied target object with the supplied arguments.
* The target object can be <code>null</code> when invoking a static {@link Method}.
*
* @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</code>)
* @return The invocation result, if any
* @throws IllegalAccessException when unable to access the specified method because access modifiers prevent it
* @throws java.lang.reflect.InvocationTargetException when a reflection invocation fails
*/
public static Object invokeMethod(final Method method, final Object target, final Object... args) throws InvocationTargetException, IllegalAccessException {
if (method == null) {
throw new IllegalArgumentException("Method must not be null.");
}
if (target == null) {
throw new IllegalArgumentException("Object must not be null.");
}
method.setAccessible(true);
return method.invoke(target, args);
}
/**
* Invoke the specified static {@link Method} with the supplied arguments.
*
* @param method The method to invoke
* @param args The invocation arguments (may be <code>null</code>)
* @return The invocation result, if any
* @throws IllegalAccessException when unable to access the specified method because access modifiers prevent it
* @throws java.lang.reflect.InvocationTargetException when a reflection invocation fails
*/
public static Object invokeStaticMethod(final Method method, final Object... args) throws InvocationTargetException, IllegalAccessException {
if (method == null) {
throw new IllegalArgumentException("Method must not be null.");
}
if (!Modifier.isStatic(method.getModifiers())) {
throw new IllegalArgumentException("Method must be static.");
}
method.setAccessible(true);
return method.invoke(null, args);
}
/**
* 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
* @see Class#getDeclaredMethods()
*/
private static Method[] getDeclaredMethods(Class<?> clazz) {
Method[] result;
Method[] declaredMethods = clazz.getDeclaredMethods();
List<Method> 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;
}
return result;
}
private static List<Method> findConcreteMethodsOnInterfaces(Class<?> clazz) {
List<Method> result = null;
for (Class<?> ifc : clazz.getInterfaces()) {
for (Method ifcMethod : ifc.getMethods()) {
if (!Modifier.isAbstract(ifcMethod.getModifiers())) {
if (result == null) {
result = new ArrayList<>();
}
result.add(ifcMethod);
}
}
}
return result;
}
}