org.springframework.web.method.annotation.ExceptionHandlerMethodResolver Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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.web.method.annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.core.ExceptionDepthComparator;
import org.springframework.core.MethodIntrospector;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ConcurrentReferenceHashMap;
import org.springframework.util.ReflectionUtils.MethodFilter;
import org.springframework.web.bind.annotation.ExceptionHandler;
/**
* Discovers {@linkplain ExceptionHandler @ExceptionHandler} methods in a given class,
* including all of its superclasses, and helps to resolve a given {@link Exception}
* to the exception types supported by a given {@link Method}.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 3.1
*/
public class ExceptionHandlerMethodResolver {
/**
* A filter for selecting {@code @ExceptionHandler} methods.
*/
public static final MethodFilter EXCEPTION_HANDLER_METHODS = method ->
AnnotatedElementUtils.hasAnnotation(method, ExceptionHandler.class);
private final Map, Method> mappedMethods = new HashMap<>(16);
private final Map, Method> exceptionLookupCache = new ConcurrentReferenceHashMap<>(16);
/**
* A constructor that finds {@link ExceptionHandler} methods in the given type.
* @param handlerType the type to introspect
*/
public ExceptionHandlerMethodResolver(Class handlerType) {
for (Method method : MethodIntrospector.selectMethods(handlerType, EXCEPTION_HANDLER_METHODS)) {
for (Class exceptionType : detectExceptionMappings(method)) {
addExceptionMapping(exceptionType, method);
}
}
}
/**
* Extract exception mappings from the {@code @ExceptionHandler} annotation first,
* and then as a fallback from the method signature itself.
*/
@SuppressWarnings("unchecked")
private List> detectExceptionMappings(Method method) {
List> result = new ArrayList<>();
detectAnnotationExceptionMappings(method, result);
if (result.isEmpty()) {
for (Class paramType : method.getParameterTypes()) {
if (Throwable.class.isAssignableFrom(paramType)) {
result.add((Class) paramType);
}
}
}
if (result.isEmpty()) {
throw new IllegalStateException("No exception types mapped to " + method);
}
return result;
}
private void detectAnnotationExceptionMappings(Method method, List> result) {
ExceptionHandler ann = AnnotatedElementUtils.findMergedAnnotation(method, ExceptionHandler.class);
Assert.state(ann != null, "No ExceptionHandler annotation");
result.addAll(Arrays.asList(ann.value()));
}
private void addExceptionMapping(Class exceptionType, Method method) {
Method oldMethod = this.mappedMethods.put(exceptionType, method);
if (oldMethod != null && !oldMethod.equals(method)) {
throw new IllegalStateException("Ambiguous @ExceptionHandler method mapped for [" +
exceptionType + "]: {" + oldMethod + ", " + method + "}");
}
}
/**
* Whether the contained type has any exception mappings.
*/
public boolean hasExceptionMappings() {
return !this.mappedMethods.isEmpty();
}
/**
* Find a {@link Method} to handle the given exception.
* Use {@link ExceptionDepthComparator} if more than one match is found.
* @param exception the exception
* @return a Method to handle the exception, or {@code null} if none found
*/
@Nullable
public Method resolveMethod(Exception exception) {
return resolveMethodByThrowable(exception);
}
/**
* Find a {@link Method} to handle the given Throwable.
* Use {@link ExceptionDepthComparator} if more than one match is found.
* @param exception the exception
* @return a Method to handle the exception, or {@code null} if none found
* @since 5.0
*/
@Nullable
public Method resolveMethodByThrowable(Throwable exception) {
Method method = resolveMethodByExceptionType(exception.getClass());
if (method == null) {
Throwable cause = exception.getCause();
if (cause != null) {
method = resolveMethodByExceptionType(cause.getClass());
}
}
return method;
}
/**
* Find a {@link Method} to handle the given exception type. This can be
* useful if an {@link Exception} instance is not available (e.g. for tools).
* @param exceptionType the exception type
* @return a Method to handle the exception, or {@code null} if none found
*/
@Nullable
public Method resolveMethodByExceptionType(Class exceptionType) {
Method method = this.exceptionLookupCache.get(exceptionType);
if (method == null) {
method = getMappedMethod(exceptionType);
this.exceptionLookupCache.put(exceptionType, method);
}
return method;
}
/**
* Return the {@link Method} mapped to the given exception type, or {@code null} if none.
*/
@Nullable
private Method getMappedMethod(Class exceptionType) {
List> matches = new ArrayList<>();
for (Class mappedException : this.mappedMethods.keySet()) {
if (mappedException.isAssignableFrom(exceptionType)) {
matches.add(mappedException);
}
}
if (!matches.isEmpty()) {
matches.sort(new ExceptionDepthComparator(exceptionType));
return this.mappedMethods.get(matches.get(0));
}
else {
return null;
}
}
}