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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.

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/*
 * Copyright 2006-2022 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.classify;

import java.util.Map;

/**
 * A special purpose {@link Classifier} with easy configuration options for mapping from
 * one arbitrary type of object to another via a pattern matcher.
 *
 * @author Dave Syer
 * @param  the type of thing to classify
 * @param  the output of the classifier
 *
 */
@SuppressWarnings("serial")
public class BackToBackPatternClassifier implements Classifier {

	private Classifier router;

	private Classifier matcher;

	/**
	 * Default constructor, provided as a convenience for people using setter injection.
	 */
	public BackToBackPatternClassifier() {
	}

	/**
	 * Set up a classifier with input to the router and output from the matcher.
	 * @param router see {@link #setRouterDelegate(Object)}
	 * @param matcher see {@link #setMatcherMap(Map)}
	 */
	public BackToBackPatternClassifier(Classifier router, Classifier matcher) {
		super();
		this.router = router;
		this.matcher = matcher;
	}

	/**
	 * A convenience method for creating a pattern matching classifier for the matcher
	 * component.
	 * @param map maps pattern keys with wildcards to output values
	 */
	public void setMatcherMap(Map map) {
		this.matcher = new PatternMatchingClassifier<>(map);
	}

	/**
	 * A convenience method of creating a router classifier based on a plain old Java
	 * Object. The object provided must have precisely one public method that either has
	 * the @Classifier annotation or accepts a single argument and outputs a
	 * String. This will be used to create an input classifier for the router component.
	 * @param delegate the delegate object used to create a router classifier
	 */
	public void setRouterDelegate(Object delegate) {
		this.router = new ClassifierAdapter<>(delegate);
	}

	/**
	 * Classify the input and map to a String, then take that and put it into a pattern
	 * matcher to match to an output value.
	 */
	@Override
	public T classify(C classifiable) {
		return this.matcher.classify(this.router.classify(classifiable));
	}

}