SpringMVC RedirectView的使用以及源码分析

看一段普通的代码，我们访问controller中的一个方法后，重定向到另外一个controller或者视图。

    @RequestMapping(params="method=index")

    public ModelAndView index() {

        RedirectView redirectView = new RedirectView("/Demo.do?method=index2", true, true);

        ModelAndView mav = new ModelAndView(redirectView);

        mav.addObject("attr1", "attr1Value");

        mav.addObject("attr2", "attr2Value");

        return mav;

    }

浏览器的URL会变成http://localhost:8080/FuDeKang/Demo.do?method=index2&attr2=attr2Value&attr1=attr1Value

也就是说Spring会自定把model中的键值放入到URL当中,那么Spring是如何做到的呢，我么还来看ModelAndViewMethodReturnValueHandler这个类。

 

public class ModelAndViewMethodReturnValueHandler implements HandlerMethodReturnValueHandler {



    public boolean supportsReturnType(MethodParameter returnType) {

        return ModelAndView.class.isAssignableFrom(returnType.getParameterType());

    }



    public void handleReturnValue(

            Object returnValue, MethodParameter returnType,

            ModelAndViewContainer mavContainer, NativeWebRequest webRequest)

            throws Exception {



        if (returnValue == null) {

            mavContainer.setRequestHandled(true);

            return;

        }



        ModelAndView mav = (ModelAndView) returnValue;

        if (mav.isReference()) {

            String viewName = mav.getViewName();

            mavContainer.setViewName(viewName);

            if (viewName != null && viewName.startsWith("redirect:")) {

                mavContainer.setRedirectModelScenario(true);

            }

        }

        else {

            View view = mav.getView();

            mavContainer.setView(view);

            if (view instanceof SmartView) {

                if (((SmartView) view).isRedirectView()) {

                    mavContainer.setRedirectModelScenario(true);

                }

            }

        }

        mavContainer.addAllAttributes(mav.getModel());

    }



}

 

其中最后一句是关键，首先modelandview当中的model数据全部放到ModelAndViewContainer 里面。

因为我们是重定向，所以无论如何底层最后产生的视图对象都是RedirectView实例，我们在看一下它的源码。

    /**

     * Convert model to request parameters and redirect to the given URL.

     * @see #appendQueryProperties

     * @see #sendRedirect

     */

    @Override

    protected void renderMergedOutputModel(

            Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)

            throws IOException {



        String targetUrl = createTargetUrl(model, request);



        targetUrl = updateTargetUrl(targetUrl, model, request, response);

        

        FlashMap flashMap = RequestContextUtils.getOutputFlashMap(request);

        if (!CollectionUtils.isEmpty(flashMap)) {

            UriComponents uriComponents = UriComponentsBuilder.fromUriString(targetUrl).build();

            flashMap.setTargetRequestPath(uriComponents.getPath());

            flashMap.addTargetRequestParams(uriComponents.getQueryParams());

        }



        FlashMapManager flashMapManager = RequestContextUtils.getFlashMapManager(request);

        flashMapManager.saveOutputFlashMap(flashMap, request, response);



        sendRedirect(request, response, targetUrl.toString(), this.http10Compatible);

    }

 

其中  targetUrl = updateTargetUrl(targetUrl, model, request, response);  是拼接了URL的代码，最后调用sendRedirect做重定向。