Generating guest access(read/write) link to an otherwise log-in requiring page

I have been working on a GWT application, which is a variation of an issue tracking system. There are some projects, which have some tickes(tasks or issues) assigned to some users. One of the requirements is to provide the administrator with an option to give access to a certain non-user person, to a specific task of a specific project. This can be a read or read/write access.

So, the question is, what are some best practices to achieve this, especially in a GWT application? Are there some specific protocols, or frameworks etc to be used. My understanding is to generate a unique(non-guessable) url token, map it to the ticket(task, issue). And also, map the token to an access type(read, read/write). Then, load the mapped ticket, with the right access type. But, i am wondering if there is a out of the box solution to this?

Solution

AFAIK there is no ready-solution in GWT.
Basically you will create a history token (i.e. http://MyGWTApp.com/tasks/#!SOME_LONG_UID).

When the user navigates to this URL, you have to check on the backend if the UID is valid. You can do this by using either RPC, RequestBuilder, or rf. Conveniently you can return the access type (red/write) back to the client.
With the access type you can then disable some UI interface elements.

Some things to keep in mind:

For each task/action that goes to the backend you have to check if the UID allows the access pattern (= never trust the client). So you also have to send along the UID with each request.
You can also have to make sure on the backend that when the anonymous users can only carry out the tasks (read/write) that are allowed (= whitelist).