GlobalExceptionResolver.java

/*
 * Copyright 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 com.springsource.greenhouse.home;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver;
import org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver;

/**
 * Handles Exceptions that are not handled at the Application Controller level.
 * Applies the global exception handling policy for the application.
 * An AccountNotConnectedException results in a 412.
 * An EmptyResultDataAccessException results in a 404.
 * Delegates to {@link ResponseStatusExceptionResolver} as a first fallback.
 * Delegates to {@link DefaultHandlerExceptionResolver} as a final fallback.
 * @author Keith Donald
 */
@Component
public class GlobalExceptionResolver implements HandlerExceptionResolver {

	private static final Logger logger = LoggerFactory.getLogger(GlobalExceptionResolver.class);
	
	private final ResponseStatusExceptionResolver annotatedExceptionHandler = new ResponseStatusExceptionResolver();
	
	private final DefaultHandlerExceptionResolver defaultExceptionHandler = new DefaultHandlerExceptionResolver();
		
	public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
		try {
			if (ex instanceof EmptyResultDataAccessException) {
				return handleEmptyResultDataAccessException((EmptyResultDataAccessException) ex, request, response, handler);
			}
		} catch (Exception e) {
			logger.warn("Handling of [" + ex.getClass().getName() + "] resulted in Exception", ex);
			return null;
		}
		ModelAndView result = annotatedExceptionHandler.resolveException(request, response, handler, ex);
		if (result != null) {
			return result;
		}
		return defaultExceptionHandler.resolveException(request, response, handler, ex);
	}

	// internal helpers
	
	private ModelAndView handleEmptyResultDataAccessException(EmptyResultDataAccessException ex,
			HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		response.sendError(HttpServletResponse.SC_NOT_FOUND);
		return new ModelAndView();
	}

}