/*
    * Copyright 2002-2014 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.mvc.method.annotation;
  
  import org.springframework.core.MethodParameter;
  import org.springframework.web.context.request.NativeWebRequest;
  import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
  import org.springframework.web.method.support.ModelAndViewContainer;
  import org.springframework.web.servlet.RequestToViewNameTranslator;
  import org.springframework.web.servlet.SmartView;
  import org.springframework.web.servlet.View;
  
  /**
   * Handles return values that are of type {@link View}.
   *
   * <p>A {@code null} return value is left as-is leaving it to the configured
   * {@link RequestToViewNameTranslator} to select a view name by convention.
   *
   * <p>A {@link View} return type has a set purpose. Therefore this handler
   * should be configured ahead of handlers that support any return value type
   * annotated with {@code @ModelAttribute} or {@code @ResponseBody} to ensure
   * they don't take over.
   *
   * @author Rossen Stoyanchev
   * @since 3.1
   */
  public class ViewMethodReturnValueHandler implements HandlerMethodReturnValueHandler {
  
  	@Override
  	public boolean supportsReturnType(MethodParameter returnType) {
  		return View.class.isAssignableFrom(returnType.getParameterType());
  	}
  
  	@Override
  	public void handleReturnValue(Object returnValue, MethodParameter returnType,
  			ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
  
  		if (returnValue == null) {
  			return;
  		}
  		else if (returnValue instanceof View){
  			View view = (View) returnValue;
  			mavContainer.setView(view);
  			if (view instanceof SmartView) {
  				if (((SmartView) view).isRedirectView()) {
  					mavContainer.setRedirectModelScenario(true);
  				}
  			}
  		}
  		else {
  			// should not happen
  			throw new UnsupportedOperationException("Unexpected return type: " +
  					returnType.getParameterType().getName() + " in method: " + returnType.getMethod());
  		}
  	}
  
  }