黑白传递模型和在jsp / gsp上使用请求对象的区别

Question

I have been working both on spring and grails (grails is built on spring).

We can pass our data from controller to view (jsp/gsp) via request object or via model.

Passing data via model is preferred because its easy.

Comparison of code :

Spring :
    controller  request.setAttribute("name","india");
    view        ${pageContext.request.getAttribute('name')}

    controller  ModelAndView("viewname",modelObject)
Grails
    controller  request.setAttribute("name","india")
    view        ${request.getAttribute("name")}

    controller  render(view:"viewName",model:[name:"india"])

I think request object does many functionalities other than this.

So my question is : If passing data from controller to view can be done with request object itself why java technology required to make a concept like model ?

necessity is mother of invention

I mean to say that there must be a task that can be implemented only via a model.

Answer 1

A few things come to mind, but they are speculation as to why.

Mainly, separation of concerns. Modifying the request , which is input, to hold output seems to be abusing this. The model is clearly ouput, and only output.

By clearly defining what constitutes output, using a model, frameworks such as Spring and Grails can then apply other processes to only the model. Grails filters come to mind, as an example.

That's my quick opinion.

Answer 2

That data which a controller gathers up and needs to make available to the view should be put in the model. That is kind of the definition of what the model is in this context. Never use request attributes for this.