viewandmodel中的数据最终序列化后写入response；
没有的话则不做处理mv != null；
@RequestMapping("/login")
public void login(User user, HttpServletResponse response){
response.getWriter.write(JSONObject.fromObject(user).toString());
}
@Override
public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response)
throws Exception {
response.setContentType(getContentType());
FileCopyUtils.copy(this.resource.getInputStream(), response.getOutputStream());
}
processDispatchResult
// Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
render(Map<String, ?>, HttpServletRequest, HttpServletResponse) : void - org.springframework.boot.autoconfigure.web.servlet.error.DefaultErrorViewResolver.HtmlResourceView
render(ModelAndView, HttpServletRequest, HttpServletResponse) : void - org.springframework.web.servlet.DispatcherServlet
processDispatchResult(HttpServletRequest, HttpServletResponse, HandlerExecutionChain, ModelAndView, Exception) : void - org.springframework.web.servlet.DispatcherServlet
render(ModelAndView, HttpServletRequest, HttpServletResponse) : void - org.springframework.test.web.servlet.TestDispatcherServlet
processDispatchResult(HttpServletRequest, HttpServletResponse, HandlerExecutionChain, ModelAndView, Exception) : void - org.springframework.web.servlet.DispatcherServlet
doDispatch(HttpServletRequest, HttpServletResponse) : void - org.springframework.web.servlet.DispatcherServlet
doService(HttpServletRequest, HttpServletResponse) : void - org.springframework.web.servlet.DispatcherServlet
processRequest(HttpServletRequest, HttpServletResponse) : void - org.springframework.web.servlet.FrameworkServlet