/*
* Copyright 2002-2013 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.messaging.handler.invocation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.core.ExceptionDepthComparator;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
/**
* Cache exception handling method mappings and provide options to look up a method
* that should handle an exception. If multiple methods match, they are sorted using
* {@link ExceptionDepthComparator} and the top match is returned.
*
* @author Rossen Stoyanchev
* @since 4.0
*/
public abstract class AbstractExceptionHandlerMethodResolver {
private static final Method NO_METHOD_FOUND = ClassUtils.getMethodIfAvailable(System.class, "currentTimeMillis");
private final Map<Class<? extends Throwable>, Method> mappedMethods = new ConcurrentHashMap<Class<? extends Throwable>, Method>(16);
private final Map<Class<? extends Throwable>, Method> exceptionLookupCache = new ConcurrentHashMap<Class<? extends Throwable>, Method>(16);
/**
* Protected constructor accepting exception-to-method mappings.
*/
protected AbstractExceptionHandlerMethodResolver(Map<Class<? extends Throwable>, Method> mappedMethods) {
Assert.notNull(mappedMethods, "Mapped Methods must not be null");
this.mappedMethods.putAll(mappedMethods);
}
/**
* Extract the exceptions this method handles.This implementation looks for
* sub-classes of Throwable in the method signature.
* The method is static to ensure safe use from sub-class constructors.
*/
@SuppressWarnings("unchecked")
protected static List<Class<? extends Throwable>> getExceptionsFromMethodSignature(Method method) {
List<Class<? extends Throwable>> result = new ArrayList<Class<? extends Throwable>>();
for (Class<?> paramType : method.getParameterTypes()) {
if (Throwable.class.isAssignableFrom(paramType)) {
result.add((Class<? extends Throwable>) paramType);
}
}
Assert.notEmpty(result, "No exception types mapped to {" + method + "}");
return result;
}
/**
* Whether the contained type has any exception mappings.
*/
public boolean hasExceptionMappings() {
return (this.mappedMethods.size() > 0);
}
/**
* Find a method to handle the given exception.
* Use {@link org.springframework.core.ExceptionDepthComparator} if more than one match is found.
* @param exception the exception
* @return a method to handle the exception or {@code null}
*/
public Method resolveMethod(Exception exception) {
Class<? extends Exception> exceptionType = exception.getClass();
Method method = this.exceptionLookupCache.get(exceptionType);
if (method == null) {
method = getMappedMethod(exceptionType);
this.exceptionLookupCache.put(exceptionType, method != null ? method : NO_METHOD_FOUND);
}
return method != NO_METHOD_FOUND ? method : null;
}
/**
* Return the method mapped to the given exception type or {@code null}.
*/
private Method getMappedMethod(Class<? extends Exception> exceptionType) {
List<Class<? extends Throwable>> matches = new ArrayList<Class<? extends Throwable>>();
for (Class<? extends Throwable> mappedException : this.mappedMethods.keySet()) {
if (mappedException.isAssignableFrom(exceptionType)) {
matches.add(mappedException);
}
}
if (!matches.isEmpty()) {
Collections.sort(matches, new ExceptionDepthComparator(exceptionType));
return this.mappedMethods.get(matches.get(0));
}
else {
return null;
}
}
}