Controllers Scopes

Available Scopes

Scopes are essentially hash like objects that allow you to store variables. The following scopes are available to controllers:

• servletContext - Also known as application scope, this scope allows you to share state across the entire web application. The servletContext is an instance of javax.servlet.ServletContext
• session - The session allows associating state with a given user and typically uses cookies to associate a session with a client. The session object is an instance of javax.servlet.HttpSession
• request - The request object allows the storage of objects for the current request only. The request object is an instance of javax.servlet.HttpServletRequest
• flash - See below.

Accessing the request parameters, session etc

Every controller has a number of properties injected into them at runtime, these make it possible to access the request, session etc. For a full reference on these please see the Dynamic Methods Reference

class BookController {
    def find = {
        def findBy = params["findBy"]
        def appContext = servletContext["appContext"]
        def loggedUser = session["logged_user"]
        // do stuff
        // return model
        return model
    };
}

Using Flash Scope

Flash scope is a concept introduced by Rails. It is a temporary store for attributes which need to be available for this request and the next request only. Afterwards the attributes are cleared. This is useful for setting a message directly before redirection, for example:

def delete = {
    def b = Book.get( params['id'] )
    if(!b) {
        flash['message'] = "User not found for id ${params['id']}"
        redirect(action:list)
    }
    … // remaining code
}