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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 bahaviour 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 2006-2007 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.springframework.retry.policy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.springframework.retry.RetryContext;
import org.springframework.retry.RetryPolicy;
import org.springframework.retry.context.RetryContextSupport;
/**
* A {@link RetryPolicy} that composes a list of other policies and delegates
* calls to them in order.
*
* @author Dave Syer
* @author Michael Minella
*
*/
@SuppressWarnings("serial")
public class CompositeRetryPolicy implements RetryPolicy {
RetryPolicy[] policies = new RetryPolicy[0];
private boolean optimistic = false;
/**
* Setter for optimistic.
*
* @param optimistic should this retry policy be optimistic
*/
public void setOptimistic(boolean optimistic) {
this.optimistic = optimistic;
}
/**
* Setter for policies.
*
* @param policies the {@link RetryPolicy} policies
*/
public void setPolicies(RetryPolicy[] policies) {
this.policies = Arrays.asList(policies).toArray(new RetryPolicy[policies.length]);
}
/**
* Delegate to the policies that were in operation when the context was
* created. If any of them cannot retry then return false, otherwise return
* true.
*
* @param context the {@link RetryContext}
* @see org.springframework.retry.RetryPolicy#canRetry(org.springframework.retry.RetryContext)
*/
@Override
public boolean canRetry(RetryContext context) {
RetryContext[] contexts = ((CompositeRetryContext) context).contexts;
RetryPolicy[] policies = ((CompositeRetryContext) context).policies;
boolean retryable = true;
if(this.optimistic) {
retryable = false;
for (int i = 0; i < contexts.length; i++) {
if (policies[i].canRetry(contexts[i])) {
retryable = true;
}
}
}
else {
for (int i = 0; i < contexts.length; i++) {
if (!policies[i].canRetry(contexts[i])) {
retryable = false;
}
}
}
return retryable;
}
/**
* Delegate to the policies that were in operation when the context was
* created. If any of them fails to close the exception is propagated (and
* those later in the chain are closed before re-throwing).
*
* @see org.springframework.retry.RetryPolicy#close(org.springframework.retry.RetryContext)
* @param context the {@link RetryContext}
*/
@Override
public void close(RetryContext context) {
RetryContext[] contexts = ((CompositeRetryContext) context).contexts;
RetryPolicy[] policies = ((CompositeRetryContext) context).policies;
RuntimeException exception = null;
for (int i = 0; i < contexts.length; i++) {
try {
policies[i].close(contexts[i]);
}
catch (RuntimeException e) {
if (exception == null) {
exception = e;
}
}
}
if (exception != null) {
throw exception;
}
}
/**
* Creates a new context that copies the existing policies and keeps a list
* of the contexts from each one.
*
* @see org.springframework.retry.RetryPolicy#open(RetryContext)
*/
@Override
public RetryContext open(RetryContext parent) {
List list = new ArrayList();
for (RetryPolicy policy : this.policies) {
list.add(policy.open(parent));
}
return new CompositeRetryContext(parent, list, this.policies);
}
/**
* Delegate to the policies that were in operation when the context was
* created.
*
* @see org.springframework.retry.RetryPolicy#close(org.springframework.retry.RetryContext)
*/
@Override
public void registerThrowable(RetryContext context, Throwable throwable) {
RetryContext[] contexts = ((CompositeRetryContext) context).contexts;
RetryPolicy[] policies = ((CompositeRetryContext) context).policies;
for (int i = 0; i < contexts.length; i++) {
policies[i].registerThrowable(contexts[i], throwable);
}
((RetryContextSupport) context).registerThrowable(throwable);
}
private static class CompositeRetryContext extends RetryContextSupport {
RetryContext[] contexts;
RetryPolicy[] policies;
public CompositeRetryContext(RetryContext parent, List contexts, RetryPolicy[] policies) {
super(parent);
this.contexts = contexts.toArray(new RetryContext[contexts.size()]);
this.policies = policies;
}
}
}