GH-244: Invoke Proxy for @Recover Method
Resolves https://github.com/spring-projects/spring-retry/issues/244

The `RecoverAnnotationRecoveryHandler` only has access to the undecorated
raw bean.

Use the `RetryContext` to make the proxy (if CGLIB) available to the recoverer.
src/main/java/org/springframework/retry/annotation/RecoverAnnotationRecoveryHandler.java
/*
 * Copyright 2013-2019 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 org.springframework.retry.annotation;

import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

import org.springframework.classify.SubclassClassifier;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.retry.ExhaustedRetryException;
import org.springframework.retry.interceptor.MethodInvocationRecoverer;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.ReflectionUtils.MethodCallback;
import org.springframework.util.StringUtils;

/**
 * A recoverer for method invocations based on the <code>@Recover</code> annotation. A
 * suitable recovery method is one with a Throwable type as the first parameter and the
 * same return type and arguments as the method that failed. The Throwable first argument
 * is optional and if omitted the method is treated as a default (called when there are no
 * other matches). Generally the best matching method is chosen based on the type of the
 * first parameter and the type of the exception being handled. The closest match in the
 * class hierarchy is chosen, so for instance if an IllegalArgumentException is being
 * handled and there is a method whose first argument is RuntimeException, then it will be
 * preferred over a method whose first argument is Throwable.
 *
 * @author Dave Syer
 * @author Josh Long
 * @author Aldo Sinanaj
 * @author Randell Callahan
 * @author Nathanaël Roberts
 * @author Maksim Kita
 * @author Gary Russell
 * @param <T> the type of the return value from the recovery
 */
public class RecoverAnnotationRecoveryHandler<T> implements MethodInvocationRecoverer<T> {

	private SubclassClassifier<Throwable, Method> classifier = new SubclassClassifier<Throwable, Method>();

	private Map<Method, SimpleMetadata> methods = new HashMap<Method, SimpleMetadata>();

	private Object target;

	private String recoverMethodName;

	public RecoverAnnotationRecoveryHandler(Object target, Method method) {
		this.target = target;
		init(target, method);
	}

	@Override
	public T recover(Object[] args, Throwable cause) {
		Method method = findClosestMatch(args, cause.getClass());
		if (method == null) {
			throw new ExhaustedRetryException("Cannot locate recovery method", cause);
		}
		SimpleMetadata meta = this.methods.get(method);
		Object[] argsToUse = meta.getArgs(cause, args);
		boolean methodAccessible = method.isAccessible();
		try {
			ReflectionUtils.makeAccessible(method);
			@SuppressWarnings("unchecked")
			T result = (T) ReflectionUtils.invokeMethod(method, this.target, argsToUse);
			return result;
		}
		finally {
			if (methodAccessible != method.isAccessible()) {
				method.setAccessible(methodAccessible);
			}
		}
	}

	private Method findClosestMatch(Object[] args, Class<? extends Throwable> cause) {
		Method result = null;

		if (StringUtils.isEmpty(this.recoverMethodName)) {
			int min = Integer.MAX_VALUE;
			for (Map.Entry<Method, SimpleMetadata> entry : this.methods.entrySet()) {
				Method method = entry.getKey();
				SimpleMetadata meta = entry.getValue();
				Class<? extends Throwable> type = meta.getType();
				if (type == null) {
					type = Throwable.class;
				}
				if (type.isAssignableFrom(cause)) {
					int distance = calculateDistance(cause, type);
					if (distance < min) {
						min = distance;
						result = method;
					}
					else if (distance == min) {
						boolean parametersMatch = compareParameters(args, meta.getArgCount(),
								method.getParameterTypes());
						if (parametersMatch) {
							result = method;
						}
					}
				}
			}
		}
		else {
			for (Map.Entry<Method, SimpleMetadata> entry : this.methods.entrySet()) {
				Method method = entry.getKey();
				if (method.getName().equals(this.recoverMethodName)) {
					SimpleMetadata meta = entry.getValue();
					if (meta.type.isAssignableFrom(cause)
							&& compareParameters(args, meta.getArgCount(), method.getParameterTypes())) {
						result = method;
						break;
					}
				}
			}
		}
		return result;
	}

	private int calculateDistance(Class<? extends Throwable> cause, Class<? extends Throwable> type) {
		int result = 0;
		Class<?> current = cause;
		while (current != type && current != Throwable.class) {
			result++;
			current = current.getSuperclass();
		}
		return result;
	}

	private boolean compareParameters(Object[] args, int argCount, Class<?>[] parameterTypes) {
		if (argCount == (args.length + 1)) {
			int startingIndex = 0;
			if (parameterTypes.length > 0 && Throwable.class.isAssignableFrom(parameterTypes[0])) {
				startingIndex = 1;
			}
			for (int i = startingIndex; i < parameterTypes.length; i++) {
				final Object argument = i - startingIndex < args.length ? args[i - startingIndex] : null;
				if (argument == null) {
					continue;
				}
				if (!parameterTypes[i].isAssignableFrom(argument.getClass())) {
					return false;
				}
			}
			return true;
		}
		return false;
	}

	private void init(final Object target, Method method) {
		final Map<Class<? extends Throwable>, Method> types = new HashMap<Class<? extends Throwable>, Method>();
		final Method failingMethod = method;
		Retryable retryable = AnnotationUtils.findAnnotation(method, Retryable.class);
		if (retryable != null) {
			this.recoverMethodName = retryable.recover();
		}
		ReflectionUtils.doWithMethods(target.getClass(), new MethodCallback() {
			@Override
			public void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {
				Recover recover = AnnotationUtils.findAnnotation(method, Recover.class);
				if (recover == null) {
					recover = findAnnotationOnTarget(target, method);
				}
				if (recover != null && failingMethod.getGenericReturnType() instanceof ParameterizedType
						&& method.getGenericReturnType() instanceof ParameterizedType) {
					if (isParameterizedTypeAssignable((ParameterizedType) method.getGenericReturnType(),
							(ParameterizedType) failingMethod.getGenericReturnType())) {
						putToMethodsMap(method, types);
					}
				}
				else if (recover != null && method.getReturnType().isAssignableFrom(failingMethod.getReturnType())) {
					putToMethodsMap(method, types);
				}
			}
		});
		this.classifier.setTypeMap(types);
		optionallyFilterMethodsBy(failingMethod.getReturnType());
	}

	/**
	 * Returns {@code true} if the input methodReturnType is a direct match of the
	 * failingMethodReturnType. Takes nested generics into consideration as well, while
	 * deciding a match.
	 * @param methodReturnType
	 * @param failingMethodReturnType
	 * @return true if the parameterized return types match.
	 * @since 1.3.2
	 */
	private boolean isParameterizedTypeAssignable(ParameterizedType methodReturnType,
			ParameterizedType failingMethodReturnType) {

		Type[] methodActualArgs = methodReturnType.getActualTypeArguments();
		Type[] failingMethodActualArgs = failingMethodReturnType.getActualTypeArguments();
		if (methodActualArgs.length != failingMethodActualArgs.length) {
			return false;
		}
		int startingIndex = 0;
		for (int i = startingIndex; i < methodActualArgs.length; i++) {
			Type methodArgType = methodActualArgs[i];
			Type failingMethodArgType = failingMethodActualArgs[i];
			if (methodArgType instanceof ParameterizedType && failingMethodArgType instanceof ParameterizedType) {
				return isParameterizedTypeAssignable((ParameterizedType) methodArgType,
						(ParameterizedType) failingMethodArgType);
			}
			if (methodArgType instanceof Class && failingMethodArgType instanceof Class
					&& !failingMethodArgType.equals(methodArgType)) {
				return false;
			}
		}
		return true;
	}

	private void putToMethodsMap(Method method, Map<Class<? extends Throwable>, Method> types) {
		Class<?>[] parameterTypes = method.getParameterTypes();
		if (parameterTypes.length > 0 && Throwable.class.isAssignableFrom(parameterTypes[0])) {
			@SuppressWarnings("unchecked")
			Class<? extends Throwable> type = (Class<? extends Throwable>) parameterTypes[0];
			types.put(type, method);
			RecoverAnnotationRecoveryHandler.this.methods.put(method, new SimpleMetadata(parameterTypes.length, type));
		}
		else {
			RecoverAnnotationRecoveryHandler.this.classifier.setDefaultValue(method);
			RecoverAnnotationRecoveryHandler.this.methods.put(method, new SimpleMetadata(parameterTypes.length, null));
		}
	}

	private Recover findAnnotationOnTarget(Object target, Method method) {
		try {
			Method targetMethod = target.getClass().getMethod(method.getName(), method.getParameterTypes());
			return AnnotationUtils.findAnnotation(targetMethod, Recover.class);
		}
		catch (Exception e) {
			return null;
		}
	}

	private void optionallyFilterMethodsBy(Class<?> returnClass) {
		Map<Method, SimpleMetadata> filteredMethods = new HashMap<Method, SimpleMetadata>();
		for (Method method : this.methods.keySet()) {
			if (method.getReturnType() == returnClass) {
				filteredMethods.put(method, this.methods.get(method));
			}
		}
		if (filteredMethods.size() > 0) {
			this.methods = filteredMethods;
		}
	}

	private static class SimpleMetadata {

		private int argCount;

		private Class<? extends Throwable> type;

		public SimpleMetadata(int argCount, Class<? extends Throwable> type) {
			super();
			this.argCount = argCount;
			this.type = type;
		}

		public int getArgCount() {
			return this.argCount;
		}

		public Class<? extends Throwable> getType() {
			return this.type;
		}

		public Object[] getArgs(Throwable t, Object[] args) {
			Object[] result = new Object[getArgCount()];
			int startArgs = 0;
			if (this.type != null) {
				result[0] = t;
				startArgs = 1;
			}
			int length = result.length - startArgs > args.length ? args.length : result.length - startArgs;
			if (length == 0) {
				return result;
			}
			System.arraycopy(args, 0, result, startArgs, length);
			return result;
		}

	}

}

/*
 * Copyright 2013-2019 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 org.springframework.retry.annotation;

import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

import org.springframework.classify.SubclassClassifier;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.retry.ExhaustedRetryException;
import org.springframework.retry.RetryContext;
import org.springframework.retry.interceptor.MethodInvocationRecoverer;
import org.springframework.retry.support.RetrySynchronizationManager;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.ReflectionUtils.MethodCallback;
import org.springframework.util.StringUtils;

/**
 * A recoverer for method invocations based on the <code>@Recover</code> annotation. A
 * suitable recovery method is one with a Throwable type as the first parameter and the
 * same return type and arguments as the method that failed. The Throwable first argument
 * is optional and if omitted the method is treated as a default (called when there are no
 * other matches). Generally the best matching method is chosen based on the type of the
 * first parameter and the type of the exception being handled. The closest match in the
 * class hierarchy is chosen, so for instance if an IllegalArgumentException is being
 * handled and there is a method whose first argument is RuntimeException, then it will be
 * preferred over a method whose first argument is Throwable.
 *
 * @author Dave Syer
 * @author Josh Long
 * @author Aldo Sinanaj
 * @author Randell Callahan
 * @author Nathanaël Roberts
 * @author Maksim Kita
 * @author Gary Russell
 * @param <T> the type of the return value from the recovery
 */
public class RecoverAnnotationRecoveryHandler<T> implements MethodInvocationRecoverer<T> {

	private SubclassClassifier<Throwable, Method> classifier = new SubclassClassifier<Throwable, Method>();

	private Map<Method, SimpleMetadata> methods = new HashMap<Method, SimpleMetadata>();

	private Object target;

	private String recoverMethodName;

	public RecoverAnnotationRecoveryHandler(Object target, Method method) {
		this.target = target;
		init(target, method);
	}

	@Override
	public T recover(Object[] args, Throwable cause) {
		Method method = findClosestMatch(args, cause.getClass());
		if (method == null) {
			throw new ExhaustedRetryException("Cannot locate recovery method", cause);
		}
		SimpleMetadata meta = this.methods.get(method);
		Object[] argsToUse = meta.getArgs(cause, args);
		boolean methodAccessible = method.isAccessible();
		try {
			ReflectionUtils.makeAccessible(method);
			RetryContext context = RetrySynchronizationManager.getContext();
			Object proxy = null;
			if (context != null) {
				proxy = context.getAttribute("___proxy___");
				if (proxy != null) {
					Method proxyMethod = findMethodOnProxy(method, proxy);
					if (proxyMethod == null) {
						proxy = null;
					}
					else {
						method = proxyMethod;
					}
				}
			}
			if (proxy == null) {
				proxy = this.target;
			}
			@SuppressWarnings("unchecked")
			T result = (T) ReflectionUtils.invokeMethod(method, proxy, argsToUse);
			return result;
		}
		finally {
			if (methodAccessible != method.isAccessible()) {
				method.setAccessible(methodAccessible);
			}
		}
	}

	private Method findMethodOnProxy(Method method, Object proxy) {
		try {
			return proxy.getClass().getMethod(method.getName(), method.getParameterTypes());
		}
		catch (NoSuchMethodException e) {
			return null;
		}
		catch (SecurityException e) {
			return null;
		}
	}

	private Method findClosestMatch(Object[] args, Class<? extends Throwable> cause) {
		Method result = null;

		if (StringUtils.isEmpty(this.recoverMethodName)) {
			int min = Integer.MAX_VALUE;
			for (Map.Entry<Method, SimpleMetadata> entry : this.methods.entrySet()) {
				Method method = entry.getKey();
				SimpleMetadata meta = entry.getValue();
				Class<? extends Throwable> type = meta.getType();
				if (type == null) {
					type = Throwable.class;
				}
				if (type.isAssignableFrom(cause)) {
					int distance = calculateDistance(cause, type);
					if (distance < min) {
						min = distance;
						result = method;
					}
					else if (distance == min) {
						boolean parametersMatch = compareParameters(args, meta.getArgCount(),
								method.getParameterTypes());
						if (parametersMatch) {
							result = method;
						}
					}
				}
			}
		}
		else {
			for (Map.Entry<Method, SimpleMetadata> entry : this.methods.entrySet()) {
				Method method = entry.getKey();
				if (method.getName().equals(this.recoverMethodName)) {
					SimpleMetadata meta = entry.getValue();
					if (meta.type.isAssignableFrom(cause)
							&& compareParameters(args, meta.getArgCount(), method.getParameterTypes())) {
						result = method;
						break;
					}
				}
			}
		}
		return result;
	}

	private int calculateDistance(Class<? extends Throwable> cause, Class<? extends Throwable> type) {
		int result = 0;
		Class<?> current = cause;
		while (current != type && current != Throwable.class) {
			result++;
			current = current.getSuperclass();
		}
		return result;
	}

	private boolean compareParameters(Object[] args, int argCount, Class<?>[] parameterTypes) {
		if (argCount == (args.length + 1)) {
			int startingIndex = 0;
			if (parameterTypes.length > 0 && Throwable.class.isAssignableFrom(parameterTypes[0])) {
				startingIndex = 1;
			}
			for (int i = startingIndex; i < parameterTypes.length; i++) {
				final Object argument = i - startingIndex < args.length ? args[i - startingIndex] : null;
				if (argument == null) {
					continue;
				}
				if (!parameterTypes[i].isAssignableFrom(argument.getClass())) {
					return false;
				}
			}
			return true;
		}
		return false;
	}

	private void init(final Object target, Method method) {
		final Map<Class<? extends Throwable>, Method> types = new HashMap<Class<? extends Throwable>, Method>();
		final Method failingMethod = method;
		Retryable retryable = AnnotationUtils.findAnnotation(method, Retryable.class);
		if (retryable != null) {
			this.recoverMethodName = retryable.recover();
		}
		ReflectionUtils.doWithMethods(target.getClass(), new MethodCallback() {
			@Override
			public void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {
				Recover recover = AnnotationUtils.findAnnotation(method, Recover.class);
				if (recover == null) {
					recover = findAnnotationOnTarget(target, method);
				}
				if (recover != null && failingMethod.getGenericReturnType() instanceof ParameterizedType
						&& method.getGenericReturnType() instanceof ParameterizedType) {
					if (isParameterizedTypeAssignable((ParameterizedType) method.getGenericReturnType(),
							(ParameterizedType) failingMethod.getGenericReturnType())) {
						putToMethodsMap(method, types);
					}
				}
				else if (recover != null && method.getReturnType().isAssignableFrom(failingMethod.getReturnType())) {
					putToMethodsMap(method, types);
				}
			}
		});
		this.classifier.setTypeMap(types);
		optionallyFilterMethodsBy(failingMethod.getReturnType());
	}

	/**
	 * Returns {@code true} if the input methodReturnType is a direct match of the
	 * failingMethodReturnType. Takes nested generics into consideration as well, while
	 * deciding a match.
	 * @param methodReturnType
	 * @param failingMethodReturnType
	 * @return true if the parameterized return types match.
	 * @since 1.3.2
	 */
	private boolean isParameterizedTypeAssignable(ParameterizedType methodReturnType,
			ParameterizedType failingMethodReturnType) {

		Type[] methodActualArgs = methodReturnType.getActualTypeArguments();
		Type[] failingMethodActualArgs = failingMethodReturnType.getActualTypeArguments();
		if (methodActualArgs.length != failingMethodActualArgs.length) {
			return false;
		}
		int startingIndex = 0;
		for (int i = startingIndex; i < methodActualArgs.length; i++) {
			Type methodArgType = methodActualArgs[i];
			Type failingMethodArgType = failingMethodActualArgs[i];
			if (methodArgType instanceof ParameterizedType && failingMethodArgType instanceof ParameterizedType) {
				return isParameterizedTypeAssignable((ParameterizedType) methodArgType,
						(ParameterizedType) failingMethodArgType);
			}
			if (methodArgType instanceof Class && failingMethodArgType instanceof Class
					&& !failingMethodArgType.equals(methodArgType)) {
				return false;
			}
		}
		return true;
	}

	private void putToMethodsMap(Method method, Map<Class<? extends Throwable>, Method> types) {
		Class<?>[] parameterTypes = method.getParameterTypes();
		if (parameterTypes.length > 0 && Throwable.class.isAssignableFrom(parameterTypes[0])) {
			@SuppressWarnings("unchecked")
			Class<? extends Throwable> type = (Class<? extends Throwable>) parameterTypes[0];
			types.put(type, method);
			RecoverAnnotationRecoveryHandler.this.methods.put(method, new SimpleMetadata(parameterTypes.length, type));
		}
		else {
			RecoverAnnotationRecoveryHandler.this.classifier.setDefaultValue(method);
			RecoverAnnotationRecoveryHandler.this.methods.put(method, new SimpleMetadata(parameterTypes.length, null));
		}
	}

	private Recover findAnnotationOnTarget(Object target, Method method) {
		try {
			Method targetMethod = target.getClass().getMethod(method.getName(), method.getParameterTypes());
			return AnnotationUtils.findAnnotation(targetMethod, Recover.class);
		}
		catch (Exception e) {
			return null;
		}
	}

	private void optionallyFilterMethodsBy(Class<?> returnClass) {
		Map<Method, SimpleMetadata> filteredMethods = new HashMap<Method, SimpleMetadata>();
		for (Method method : this.methods.keySet()) {
			if (method.getReturnType() == returnClass) {
				filteredMethods.put(method, this.methods.get(method));
			}
		}
		if (filteredMethods.size() > 0) {
			this.methods = filteredMethods;
		}
	}

	private static class SimpleMetadata {

		private int argCount;

		private Class<? extends Throwable> type;

		public SimpleMetadata(int argCount, Class<? extends Throwable> type) {
			super();
			this.argCount = argCount;
			this.type = type;
		}

		public int getArgCount() {
			return this.argCount;
		}

		public Class<? extends Throwable> getType() {
			return this.type;
		}

		public Object[] getArgs(Throwable t, Object[] args) {
			Object[] result = new Object[getArgCount()];
			int startArgs = 0;
			if (this.type != null) {
				result[0] = t;
				startArgs = 1;
			}
			int length = result.length - startArgs > args.length ? args.length : result.length - startArgs;
			if (length == 0) {
				return result;
			}
			System.arraycopy(args, 0, result, startArgs, length);
			return result;
		}

	}

}

1. Good point; I was just being lazy to get a quick fix out.
2. Yes, we can add code to find the corresponding method on the proxy (if it exists). The problem is it won't solve every use case because the proxied interfaces may not expose the recover method. So we'd still need to handle the case where we call the recover method directly on the target instead of the proxy.