fixed @ExceptionHandler resolution in case of multiple matches at different inheritance levels (SPR-7085)

org.springframework.core/src/main/java/org/springframework/core/ExceptionDepthComparator.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2002-2010 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.core;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import org.springframework.util.Assert;
+
+/**
+ * Comparator capable of sorting exceptions based on their depth from the thrown exception type.
+ *
+ * @author Juergen Hoeller
+ * @author Arjen Poutsma
+ * @since 3.0.3
+ */
+public class ExceptionDepthComparator implements Comparator<Class<? extends Throwable>> {
+
+	private final Class<? extends Throwable> targetException;
+
+
+	/**
+	 * Create a new ExceptionDepthComparator for the given exception.
+	 * @param exception the target exception to compare to when sorting by depth
+	 */
+	public ExceptionDepthComparator(Throwable exception) {
+		Assert.notNull(exception, "Target exception must not be null");
+		this.targetException = exception.getClass();
+	}
+
+	/**
+	 * Create a new ExceptionDepthComparator for the given exception type.
+	 * @param exceptionType the target exception type to compare to when sorting by depth
+	 */
+	public ExceptionDepthComparator(Class<? extends Throwable> exceptionType) {
+		Assert.notNull(exceptionType, "Target exception type must not be null");
+		this.targetException = exceptionType;
+	}
+
+
+	public int compare(Class<? extends Throwable> o1, Class<? extends Throwable> o2) {
+		int depth1 = getDepth(o1, this.targetException, 0);
+		int depth2 = getDepth(o2, this.targetException, 0);
+		return (depth1 - depth2);
+	}
+
+	private int getDepth(Class declaredException, Class exceptionToMatch, int depth) {
+		if (declaredException.equals(exceptionToMatch)) {
+			// Found it!
+			return depth;
+		}
+		// If we've gone as far as we can go and haven't found it...
+		if (Throwable.class.equals(exceptionToMatch)) {
+			return -1;
+		}
+		return getDepth(declaredException, exceptionToMatch.getSuperclass(), depth + 1);
+	}
+
+
+	/**
+	 * Obtain the closest match from the given exception types for the given target exception.
+	 * @param exceptionTypes the collection of exception types
+	 * @param targetException the target exception to find a match for
+	 * @return the closest matching exception type from the given collection
+	 */
+	public static Class<? extends Throwable> findClosestMatch(
+			Collection<Class<? extends Throwable>> exceptionTypes, Throwable targetException) {
+
+		Assert.notEmpty(exceptionTypes, "Exception types must not be empty");
+		if (exceptionTypes.size() == 1) {
+			return exceptionTypes.iterator().next();
+		}
+		List<Class<? extends Throwable>> handledExceptions =
+				new ArrayList<Class<? extends Throwable>>(exceptionTypes);
+		Collections.sort(handledExceptions, new ExceptionDepthComparator(targetException));
+		return handledExceptions.get(0);
+	}
+
+}