001/*
002 * Copyright 2002-2012 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.Collections;
022import java.util.Comparator;
023import java.util.List;
024
025import org.springframework.util.Assert;
026
027/**
028 * Comparator capable of sorting exceptions based on their depth from the thrown exception type.
029 *
030 * @author Juergen Hoeller
031 * @author Arjen Poutsma
032 * @since 3.0.3
033 */
034public class ExceptionDepthComparator implements Comparator<Class<? extends Throwable>> {
035
036        private final Class<? extends Throwable> targetException;
037
038
039        /**
040         * Create a new ExceptionDepthComparator for the given exception.
041         * @param exception the target exception to compare to when sorting by depth
042         */
043        public ExceptionDepthComparator(Throwable exception) {
044                Assert.notNull(exception, "Target exception must not be null");
045                this.targetException = exception.getClass();
046        }
047
048        /**
049         * Create a new ExceptionDepthComparator for the given exception type.
050         * @param exceptionType the target exception type to compare to when sorting by depth
051         */
052        public ExceptionDepthComparator(Class<? extends Throwable> exceptionType) {
053                Assert.notNull(exceptionType, "Target exception type must not be null");
054                this.targetException = exceptionType;
055        }
056
057
058        @Override
059        public int compare(Class<? extends Throwable> o1, Class<? extends Throwable> o2) {
060                int depth1 = getDepth(o1, this.targetException, 0);
061                int depth2 = getDepth(o2, this.targetException, 0);
062                return (depth1 - depth2);
063        }
064
065        private int getDepth(Class<?> declaredException, Class<?> exceptionToMatch, int depth) {
066                if (exceptionToMatch.equals(declaredException)) {
067                        // Found it!
068                        return depth;
069                }
070                // If we've gone as far as we can go and haven't found it...
071                if (exceptionToMatch == Throwable.class) {
072                        return Integer.MAX_VALUE;
073                }
074                return getDepth(declaredException, exceptionToMatch.getSuperclass(), depth + 1);
075        }
076
077
078        /**
079         * Obtain the closest match from the given exception types for the given target exception.
080         * @param exceptionTypes the collection of exception types
081         * @param targetException the target exception to find a match for
082         * @return the closest matching exception type from the given collection
083         */
084        public static Class<? extends Throwable> findClosestMatch(
085                        Collection<Class<? extends Throwable>> exceptionTypes, Throwable targetException) {
086
087                Assert.notEmpty(exceptionTypes, "Exception types must not be empty");
088                if (exceptionTypes.size() == 1) {
089                        return exceptionTypes.iterator().next();
090                }
091                List<Class<? extends Throwable>> handledExceptions =
092                                new ArrayList<Class<? extends Throwable>>(exceptionTypes);
093                Collections.sort(handledExceptions, new ExceptionDepthComparator(targetException));
094                return handledExceptions.get(0);
095        }
096
097}