Cookies — yada/core 1.3.0-alpha12

HTTP is a stateless protocol but often there is a need to preserve state between requests.

RFC 6265: HTTP State Management Mechanism defines the HTTP Cookie and Set-Cookie headers which can used to store state in user-agents which can be transferred via requests.

This chapter describes yada's support for cookies.

Cookies can be declared in the resource map under the :cookies entry.

Example 1. Declaring a cookie

The following code declares a cookie:

{:cookies
  {:session
    {:name "session"
     :max-age 3600
     :domain "example.com"
     :path "/"
     :secure true
     :http-only true}}}

Setting cookies

Once you have declared a cookie in your resource, you can set the cookie to a new value by using the set-cookie function.

Example 2. Setting a cookie

The following code has a :get method that returns a response that contains a Set-Cookie header to set a cookie named session.

{:cookies
  {:session ; (1)
    {:name      "session"
     :max-age   3600
     :domain    "example.com"
     :path      "/"
     :secure    true
     :http-only true
     :same-site :lax}}

 :methods
  {:get
    {:response
      (fn [ctx]
         (yada/set-cookie ctx :session ; (2)
         "123" ; (3)
         ))}}}

1	A cookie is declared called `:session`. Here, it has a name of `session` which is how it will be named in the user-agent.
2	The `set-cookie` function is called. It takes the yada `ctx` and returns a modified `ctx` with the `:session` cookie set on the response. It is legal to return a `ctx` as the return value of a response function.
3	The value of the cookie is set to "123".

Consuming a cookie

Once a cookie is declared on a resource, it is possible to register a callback on the cookie that will be called with the cookie and its value if the cookie is present in the request.

Example 3. Consuming a cookie

{:cookies
  {:session
    {:name "session"
     :max-age 3600
     :domain "example.com"
     :path "/"
     :secure true
     :http-only true
     :consumer (fn [ctx cookie v] ctx) ; (1)
     }}}

1 If the session cookie is sent in the request, this 3-arg callback function will be called. The first argument is the yada context, which should also be returned, possibly augmented. The second argument is the cookie declaration itself, for convenience. The final argument is the value of the cookie in the request.