com.gitee.l0km.common.spring.util.ReflectionUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2021 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
*
* https://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 com.gitee.l0km.common.spring.util;
import java.lang.reflect.Field;
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.List;
import java.util.Map;
/**
* 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
*/
public abstract class ReflectionUtils {
/**
* Pre-built MethodFilter that matches all non-bridge non-synthetic methods
* which are not declared on {@code java.lang.Object}.
*/
public static final MethodFilter USER_DECLARED_METHODS = new MethodFilter() {
@Override
public boolean matches(Method method) {
return !method.isBridge() && !method.isSynthetic();
}};
private static final Class[] EMPTY_CLASS_ARRAY = new Class[0];
private static final Method[] EMPTY_METHOD_ARRAY = new Method[0];
private static final Field[] EMPTY_FIELD_ARRAY = new Field[0];
private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];
/**
* 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);
/**
* Cache for {@link Class#getDeclaredFields()}, allowing for fast iteration.
*/
private static final Map, Field[]> declaredFieldsCache = new ConcurrentReferenceHashMap<>(256);
// Exception handling
/**
* Handle the given reflection exception.
* Should only be called if no checked exception is expected to be thrown
* by a target method, or if an error occurs while accessing a method or field.
*
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 or field: " + 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);
}
/**
* 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 an {@link Exception} or
* {@link Error} if appropriate; otherwise, throws an
* {@link UndeclaredThrowableException}.
* @param ex the exception to rethrow
* @throws Exception the rethrown exception (in case of a checked exception)
*/
public static void rethrowException(Throwable ex) throws Exception {
if (ex instanceof Exception) {
throw (Exception) ex;
}
if (ex instanceof Error) {
throw (Error) ex;
}
throw new UndeclaredThrowableException(ex);
}
// Constructor handling
// Method handling
/**
* 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
*/
public static Method findMethod(Class clazz, String name) {
return findMethod(clazz, name, EMPTY_CLASS_ARRAY);
}
/**
* 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
*/
public static Method findMethod(Class clazz, String name, 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, false));
for (Method method : methods) {
if (name.equals(method.getName()) && (paramTypes == null || hasSameParams(method, paramTypes))) {
return method;
}
}
searchType = searchType.getSuperclass();
}
return null;
}
private static boolean hasSameParams(Method method, Class[] paramTypes) {
return (paramTypes.length == method.getParameterTypes().length &&
Arrays.equals(paramTypes, method.getParameterTypes()));
}
/**
* 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[])
*/
public static Object invokeMethod(Method method, Object target) {
return invokeMethod(method, target, EMPTY_OBJECT_ARRAY);
}
/**
* 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
*/
public static Object invokeMethod(Method method, Object target, Object... args) {
try {
return method.invoke(target, args);
}
catch (Exception ex) {
handleReflectionException(ex);
}
throw new IllegalStateException("Should never get here");
}
/**
* 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, MethodFilter mf) {
// Keep backing up the inheritance hierarchy.
Method[] methods = getDeclaredMethods(clazz, false);
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 && (mf != USER_DECLARED_METHODS || clazz.getSuperclass() != Object.class)) {
doWithMethods(clazz.getSuperclass(), mc, mf);
}
else if (clazz.isInterface()) {
for (Class superIfc : clazz.getInterfaces()) {
doWithMethods(superIfc, mc, mf);
}
}
}
/**
* Perform the given callback operation on all matching methods of the given
* class, as locally declared or equivalent thereof (such as default methods
* on Java 8 based interfaces that the given class implements).
* @param clazz the class to introspect
* @param mc the callback to invoke for each method
* @throws IllegalStateException if introspection fails
* @see #doWithMethods
*/
public static void doWithLocalMethods(Class clazz, MethodCallback mc) {
Method[] methods = getDeclaredMethods(clazz, false);
for (Method method : methods) {
try {
mc.doWith(method);
}
catch (IllegalAccessException ex) {
throw new IllegalStateException("Not allowed to access method '" + method.getName() + "': " + ex);
}
}
}
/**
* Variant of {@link Class#getDeclaredMethods()} that uses a local cache in
* order to avoid the JVM's SecurityManager check and new Method instances.
* 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()
*/
public static Method[] getDeclaredMethods(Class clazz) {
return getDeclaredMethods(clazz, true);
}
private static Method[] getDeclaredMethods(Class clazz, boolean defensive) {
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 ? EMPTY_METHOD_ARRAY : result));
}
catch (Throwable ex) {
throw new IllegalStateException("Failed to introspect Class [" + clazz.getName() +
"] from ClassLoader [" + clazz.getClassLoader() + "]", ex);
}
}
return (result.length == 0 || !defensive) ? result : result.clone();
}
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 ArrayList<>();
}
result.add(ifcMethod);
}
}
}
return result;
}
/**
* Determine whether the given method is an "equals" method.
* @see java.lang.Object#equals(Object)
*/
public static boolean isEqualsMethod(Method method) {
if (method == null) {
return false;
}
if (method.getParameterTypes().length != 1) {
return false;
}
if (!method.getName().equals("equals")) {
return false;
}
return method.getParameterTypes()[0] == Object.class;
}
/**
* Determine whether the given method is a "hashCode" method.
* @see java.lang.Object#hashCode()
*/
public static boolean isHashCodeMethod(Method method) {
return method != null && method.getParameterTypes().length == 0 && method.getName().equals("hashCode");
}
/**
* Determine whether the given method is a "toString" method.
* @see java.lang.Object#toString()
*/
public static boolean isToStringMethod(Method method) {
return (method != null && method.getParameterTypes().length == 0 && method.getName().equals("toString"));
}
/**
* 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);
}
}
// Field handling
/**
* Attempt to find a {@link Field field} on the supplied {@link Class} with the
* supplied {@code name}. Searches all superclasses up to {@link Object}.
* @param clazz the class to introspect
* @param name the name of the field
* @return the corresponding Field object, or {@code null} if not found
*/
public static Field findField(Class clazz, String name) {
return findField(clazz, name, null);
}
/**
* Attempt to find a {@link Field field} on the supplied {@link Class} with the
* supplied {@code name} 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} if type is specified)
* @param type the type of the field (may be {@code null} if name is specified)
* @return the corresponding Field object, or {@code null} if not found
*/
public static Field findField(Class clazz, String name, Class type) {
Assert.notNull(clazz, "Class must not be null");
Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified");
Class searchType = clazz;
while (Object.class != searchType && searchType != null) {
Field[] fields = getDeclaredFields(searchType);
for (Field field : fields) {
if ((name == null || name.equals(field.getName())) &&
(type == null || type.equals(field.getType()))) {
return field;
}
}
searchType = searchType.getSuperclass();
}
return null;
}
/**
* This variant retrieves {@link Class#getDeclaredFields()} from a local cache
* in order to avoid the JVM's SecurityManager check and defensive array copying.
* @param clazz the class to introspect
* @return the cached array of fields
* @throws IllegalStateException if introspection fails
* @see Class#getDeclaredFields()
*/
private static Field[] getDeclaredFields(Class clazz) {
Assert.notNull(clazz, "Class must not be null");
Field[] result = declaredFieldsCache.get(clazz);
if (result == null) {
try {
result = clazz.getDeclaredFields();
declaredFieldsCache.put(clazz, (result.length == 0 ? EMPTY_FIELD_ARRAY : result));
}
catch (Throwable ex) {
throw new IllegalStateException("Failed to introspect Class [" + clazz.getName() +
"] from ClassLoader [" + clazz.getClassLoader() + "]", ex);
}
}
return result;
}
/**
* Determine whether the given field is a "public static final" constant.
* @param field the field to check
*/
public static boolean isPublicStaticFinal(Field field) {
int modifiers = field.getModifiers();
return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers));
}
// Cache handling
/**
* Clear the internal method/field cache.
*/
public static void clearCache() {
declaredMethodsCache.clear();
declaredFieldsCache.clear();
}
/**
* Action to take on each method.
*/
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.
*/
public interface MethodFilter {
/**
* Determine whether the given method matches.
* @param method the method to check
*/
boolean matches(Method method);
}
/**
* Callback interface invoked on each field in the hierarchy.
*/
public interface FieldCallback {
/**
* Perform an operation using the given field.
* @param field the field to operate on
*/
void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
}
}