/*
 * Copyright 2002-2017 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.servlet.handler;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.lang.Nullable;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.ModelAndView;

Abstract base class for HandlerExceptionResolver implementations that support handling exceptions from handlers of type HandlerMethod. 
Author:
Rossen Stoyanchev
Since:
3.1/**
 * Abstract base class for
 * {@link org.springframework.web.servlet.HandlerExceptionResolver HandlerExceptionResolver}
 * implementations that support handling exceptions from handlers of type {@link HandlerMethod}.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public abstract class AbstractHandlerMethodExceptionResolver extends AbstractHandlerExceptionResolver {

	
Checks if the handler is a HandlerMethod and then delegates to the base class implementation of #shouldApplyTo(HttpServletRequest, Object) passing the bean of the HandlerMethod. Otherwise returns false. /**
	 * Checks if the handler is a {@link HandlerMethod} and then delegates to the
	 * base class implementation of {@code #shouldApplyTo(HttpServletRequest, Object)}
	 * passing the bean of the {@code HandlerMethod}. Otherwise returns {@code false}.
	 */
	@Override
	protected boolean shouldApplyTo(HttpServletRequest request, @Nullable Object handler) {
		if (handler == null) {
			return super.shouldApplyTo(request, null);
		}
		else if (handler instanceof HandlerMethod) {
			HandlerMethod handlerMethod = (HandlerMethod) handler;
			handler = handlerMethod.getBean();
			return super.shouldApplyTo(request, handler);
		}
		else {
			return false;
		}
	}

	@Override
	@Nullable
	protected final ModelAndView doResolveException(
			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) {

		return doResolveHandlerMethodException(request, response, (HandlerMethod) handler, ex);
	}

	
Actually resolve the given exception that got thrown during on handler execution,
returning a ModelAndView that represents a specific error page if appropriate.
May be overridden in subclasses, in order to apply specific exception checks.
Note that this template method will be invoked after checking whether this
resolved applies ("mappedHandlers" etc), so an implementation may simply proceed
with its actual exception handling.
Params:
request – current HTTP request
response – current HTTP response
handlerMethod – the executed handler method, or null if none chosen at the time of the exception (for example, if multipart resolution failed)
ex – the exception that got thrown during handler execution
Returns:
a corresponding ModelAndView to forward to, or null for default processing/**
	 * Actually resolve the given exception that got thrown during on handler execution,
	 * returning a ModelAndView that represents a specific error page if appropriate.
	 * <p>May be overridden in subclasses, in order to apply specific exception checks.
	 * Note that this template method will be invoked <i>after</i> checking whether this
	 * resolved applies ("mappedHandlers" etc), so an implementation may simply proceed
	 * with its actual exception handling.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @param handlerMethod the executed handler method, or {@code null} if none chosen at the time
	 * of the exception (for example, if multipart resolution failed)
	 * @param ex the exception that got thrown during handler execution
	 * @return a corresponding ModelAndView to forward to, or {@code null} for default processing
	 */
	@Nullable
	protected abstract ModelAndView doResolveHandlerMethodException(
			HttpServletRequest request, HttpServletResponse response, @Nullable HandlerMethod handlerMethod, Exception ex);

}