Explore how @ modelandview can forward data and pages through the source code

First of all ModelAndView Enclosed model Data and view name , stay return Break points in sentences ,url Access to controller,
Back in ModelAndView Before the object ,springmvc Will call first DispatcherServlet Class doDispatch Method ,

In this method, there is through HandlerAdapter obtain controller in ModelAndView Object method ha.handle()：


When debug When the method is


You can see the mv The object is null, When you're done with this ha.handle() Look after the method mv：

model Data in and view I got all the view names , Walk the ha.handle() After method , Enter into DispatcherServlet Class processDispatchResult()

You can see that the middle note is called in this method. this.render(mv, request, response); Method , Judge mv Enter after object render In submission method , See the call in this method view.render() Method ,mv.getModelInternal() Is to get model data ;

Get into view.render() Method ：

The call this.renderMergedOutputModel(), Enter this method ：

It calls two key methods ,this.exposeModelAsRequestAttributes(model, request); And rd.forward(request, response);, The second method is easy to identify ,rd Namely request Of RequestDispatcher call forward Forward page , You can guess exposeModelAsRequestAttributes() The way is to put model The data in request, Get into exposeModelAsRequestAttributes()：

In this method, we see request.setAttribute(modelName, modelValue);, It can be confirmed that the method is to model Data assignment request;

The following is a diagram to illustrate the process ：