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Spring Retry provides an abstraction around retrying failed operations, with an
emphasis on declarative control of the process and policy-based behaviour that is
easy to extend and customize. For instance, you can configure a plain POJO
operation to retry if it fails, based on the type of exception, and with a fixed
or exponential backoff.
/*
* 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.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;
/**
* A recoverer for method invocations based on the @Recover 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
* @param the type of the return value from the recovery
*/
public class RecoverAnnotationRecoveryHandler implements MethodInvocationRecoverer {
private SubclassClassifier classifier = new SubclassClassifier();
private Map methods = new HashMap();
private Object target;
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 cause) {
int min = Integer.MAX_VALUE;
Method result = null;
for (Method method : this.methods.keySet()) {
SimpleMetadata meta = this.methods.get(method);
Class 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;
}
}
}
}
return result;
}
private int calculateDistance(Class cause,
Class 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(Object target, Method method) {
final Map, Method> types = new HashMap, Method>();
final Method failingMethod = method;
ReflectionUtils.doWithMethods(failingMethod.getDeclaringClass(),
new MethodCallback() {
@Override
public void doWith(Method method)
throws IllegalArgumentException, IllegalAccessException {
Recover recover = AnnotationUtils.findAnnotation(method,
Recover.class);
if (recover != null && method.getReturnType()
.isAssignableFrom(failingMethod.getReturnType())) {
Class[] parameterTypes = method.getParameterTypes();
if (parameterTypes.length > 0 && Throwable.class
.isAssignableFrom(parameterTypes[0])) {
@SuppressWarnings("unchecked")
Class type = (Class) 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));
}
}
}
});
this.classifier.setTypeMap(types);
optionallyFilterMethodsBy(failingMethod.getReturnType());
}
private void optionallyFilterMethodsBy(Class returnClass) {
Map filteredMethods = new HashMap();
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 type;
public SimpleMetadata(int argCount, Class type) {
super();
this.argCount = argCount;
this.type = type;
}
public int getArgCount() {
return this.argCount;
}
public Class 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;
}
}
}