Groovy on rails 入门 （C -1）

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     Grails中的跳转页面大概有以下几种方式：

1. return model

def show = {
    def b = Book.get( params['id'] )
    return [ book : b ]
}

没有显式返回model时，action会自动把当前controller的property当作model返回，而模版的地址则为<...>/controller/action.gsp

2. return view

import org.springframework.web.servlet.ModelAndView

...

def index = {
    def favBooks = // get some books just for the index page, perhaps your favorites

    // forward to the list view to show them
    return new ModelAndView("/book/list", [ bookList : favBooks ])
}

3. redirect

redirect(action:list)

当跳转到另一个controller的action时，最好使用这种方式，也可以带参数，如：

redirect(controller:'apartment',action:'show',id:apartment.id)

4. render

// write some markup
render {
   for(b in books) {
      div(id:b.id, b.title)
   }
}
// render a specific view
render(view:'show')
// render a template for each item in a collection
render(template:'book_template', collection:Book.list())
// render some text with encoding and content type
render(text:",contentType:"text/xml",encoding:"UTF-8")

     Grails中变量的scope分类和传统的jsp大致相同，分为servletContext, session, request, flash. 比较新颖的是flash，意思是在当前request和下一个request中保持，这样一来处理消息和错误就非常方便了。

def findBy = params["findBy"]
def appContext = servletContext["appContext"]
def loggedUser = session["logged_user"]
flash['message'] = "User not found for id ${params['id']}"

    因此，request的信息，grails不会像OGNL那样设置到controller中去，而要从params里面取，比如params.id 。