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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
*
* 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.feilong.lib.springframework.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
* @since 1.2.2
*/
public abstract class ReflectionUtils{
private static final Method[] NO_METHODS = {};
private static final Field[] NO_FIELDS = {};
/**
* 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);
/**
* 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;
}
/**
* 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.
*
* Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}.
*
* @param field
* the field to get
* @param target
* the target object from which to get the field
* @return the field's current value
*/
public static Object getField(Field field,Object target){
try{
return field.get(target);
}catch (IllegalAccessException ex){
handleReflectionException(ex);
throw new IllegalStateException("Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
}
}
/**
* 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, 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
*/
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));
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[])
*/
public static Object invokeMethod(Method method,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
*/
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");
}
/**
* 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);
}
/**
* 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){
Assert.notNull(clazz, "Class must not be null");
Method[] result = declaredMethodsCache.get(clazz);
if (result == null){
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));
}
return result;
}
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;
}
/**
* 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
* @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){
result = clazz.getDeclaredFields();
declaredFieldsCache.put(clazz, (result.length == 0 ? NO_FIELDS : result));
}
return result;
}
}