Controller handler method supported return types

Question

While learning the Spring framework, I notice in the book Spring in Action, the author doesn\'t use ModelandView method return type in controllers. The aut

Answer 1

In spring source code, you can see this class org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter. In the method public ModelAndView getModelAndView(...), you can get how sping-mvc generate ModelAandView object.

if (returnValue instanceof HttpEntity) { // returnValue is returned Value of Handler method
            handleHttpEntityResponse((HttpEntity) returnValue, webRequest);
            return null;
        }
        else if (AnnotationUtils.findAnnotation(handlerMethod, ResponseBody.class) != null) {
            handleResponseBody(returnValue, webRequest);
            return null;
        }
        else if (returnValue instanceof ModelAndView) {
            ModelAndView mav = (ModelAndView) returnValue;
            mav.getModelMap().mergeAttributes(implicitModel);
            return mav;
        }
        else if (returnValue instanceof Model) {
            return new ModelAndView().addAllObjects(implicitModel).addAllObjects(((Model) returnValue).asMap());
        }
        else if (returnValue instanceof View) {
            return new ModelAndView((View) returnValue).addAllObjects(implicitModel);
        }
        else if (AnnotationUtils.findAnnotation(handlerMethod, ModelAttribute.class) != null) {
            addReturnValueAsModelAttribute(handlerMethod, handlerType, returnValue, implicitModel);
            return new ModelAndView().addAllObjects(implicitModel);
        }
        else if (returnValue instanceof Map) {
            return new ModelAndView().addAllObjects(implicitModel).addAllObjects((Map) returnValue);
        }
        else if (returnValue instanceof String) { // String is here, return new ModelAndView
            return new ModelAndView((String) returnValue).addAllObjects(implicitModel);
        }

So in this method you can learn that spring-mvc can handle many returned types of handler method to build ModleAndView object.