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The Spring Batch Infrastructure is a set of low-level components, interfaces and tools for batch processing applications and optimisations.

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/*
 * 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.batch.retry;


/**
 * A {@link RetryPolicy} is responsible for allocating and managing resources
 * needed by {@link RetryOperations}. The {@link RetryPolicy} allows retry
 * operations to be aware of their context. Context can be internal to the retry
 * framework, e.g. to support nested retries. Context can also be external, and
 * the {@link RetryPolicy} provides a uniform API for a range of different
 * platforms for the external context.
 * 
 * @author Dave Syer
 * 
 */
public interface RetryPolicy {

	/**
	 * @param context the current retry status
	 * @return true if the operation can proceed
	 */
	boolean canRetry(RetryContext context);

	/**
	 * @param context the current context.
	 * @return true if the policy determines that the last exception should be
	 * re-thrown.
	 */
	boolean shouldRethrow(RetryContext context);

	/**
	 * Acquire resources needed for the retry operation. The callback is passed
	 * in so that marker interfaces can be used and a manager can collaborate
	 * with the callback to set up some state in the status token.
	 * 
	 * @param callback the {@link RetryCallback} that will execute the unit of
	 * work for this retry.
	 * @param parent the parent context if we are in a nested retry.
	 * @return a {@link RetryContext} object specific to this manager.
	 * 
	 */
	RetryContext open(RetryCallback callback, RetryContext parent);

	/**
	 * @param context a retry status created by the {@link #open(RetryCallback, RetryContext)}
	 * method of this manager.
	 */
	void close(RetryContext context);

	/**
	 * Called once per retry attempt, after the callback fails.
	 * 
	 * @param context the current status object.
	 * 
	 * @throws TerminatedRetryException if the status is set to terminate only.
	 * 
	 */
	void registerThrowable(RetryContext context, Throwable throwable) throws TerminatedRetryException;

	/**
	 * Handle an exhausted retry. Default will be to throw an exception, but
	 * implementations may provide recovery path.
	 * 
	 * @param context the current retry context.
	 * @return an appropriate value possibly from the callback.
	 * 
	 * @throws ExhaustedRetryException if there is no recovery path.
	 */
	Object handleRetryExhausted(RetryContext context) throws ExhaustedRetryException;
}