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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.HashMap;
import java.util.Map;

/**
 * A {@link Classifier} that maps from String patterns with wildcards to a set of values
 * of a given type. An input String is matched with the most specific pattern possible to
 * the corresponding value in an input map. A default value should be specified with a
 * pattern key of "*".
 *
 * @author Dave Syer
 * @param  the output of the classifier
 */
@SuppressWarnings("serial")
public class PatternMatchingClassifier implements Classifier {

	private PatternMatcher values;

	/**
	 * Default constructor. Use the setter or the other constructor to create a sensible
	 * classifier, otherwise all inputs will cause an exception.
	 */
	public PatternMatchingClassifier() {
		this(new HashMap<>());
	}

	/**
	 * Create a classifier from the provided map. The keys are patterns, using '?' as a
	 * single character and '*' as multi-character wildcard.
	 * @param values the values to use in the {@link PatternMatcher}
	 */
	public PatternMatchingClassifier(Map values) {
		super();
		this.values = new PatternMatcher<>(values);
	}

	/**
	 * A map from pattern to value
	 * @param values the pattern map to set
	 */
	public void setPatternMap(Map values) {
		this.values = new PatternMatcher<>(values);
	}

	/**
	 * Classify the input by matching it against the patterns provided in
	 * {@link #setPatternMap(Map)}. The most specific pattern that matches will be used to
	 * locate a value.
	 * @return the value matching the most specific pattern possible
	 * @throws IllegalStateException if no matching value is found.
	 */
	@Override
	public T classify(String classifiable) {
		T value = this.values.match(classifiable);
		return value;
	}

}