@@ -474,7 +476,7 @@
For the actual request processing, the Records are unwrapped into normal functions and composed into a middleware function chain, yielding zero runtime penalty.
Creating Middleware
The following produce identical middleware runtime function.
-Function
+Function
(defn wrap [handler id]
(fn [request]
(handler (update request ::acc (fnil conj []) id))))
@@ -488,13 +490,14 @@
:description "Middleware that does things."
:wrap wrap}))
-Map
+Map
(def wrap3
{:name ::wrap3
:description "Middleware that does things."
:wrap wrap})
-Using Middleware
+Using Middleware
+:middleware is merged to endpoints by the router.
(require '[reitit.ring :as ring])
(defn handler [{:keys [::acc]}]
@@ -507,14 +510,43 @@
["/ping" {:get {:middleware [[wrap3 3]]
:handler handler}}]])))
-All the middleware are called correctly:
+All the middleware are applied correctly:
(app {:request-method :get, :uri "/api/ping"})
-Future
+Compiling middleware
+Middleware can be optimized against an endpoint using middleware compilation.
+
+There is an extra option in ring-router (actually, in the undelaying middleware-router): :reitit.ring.middleware/transform to transform the middleware chain per endpoint. It sees the vector of compiled middleware and should return a new vector of middleware.
+Adding debug middleware between all other middleware
+(def app
+ (ring/ring-handler
+ (ring/router
+ ["/api" {:middleware [[wrap 1] [wrap2 2]]}
+ ["/ping" {:get {:middleware [[wrap3 3]]
+ :handler handler}}]]
+ {::middleware/transform #(interleave % (repeat [wrap :debug]))})))
+
+(app {:request-method :get, :uri "/api/ping"})
+; {:status 200, :body [1 :debug 2 :debug 3 :debug :handler]}
+
Reversing the middleware chain
+(def app
+ (ring/ring-handler
+ (ring/router
+ ["/api" {:middleware [[wrap 1] [wrap2 2]]}
+ ["/ping" {:get {:middleware [[wrap3 3]]
+ :handler handler}}]]
+ {::middleware/transform reverse)})))
+
+(app {:request-method :get, :uri "/api/ping"})
+; {:status 200, :body [3 2 1 :handler]}
+
Roadmap for middleware
Some things bubblin' under:
-- Hooks to manipulate the
:middleware chain before compilation
+- Re-package all useful middleware into (optimized) data-driven Middleware
+- just package or a new community-repo with rehosting stuffm?
+
+
- Support
Keyword expansion into Middleware, enabling external Middleware Registries (duct/integrant/macchiato -style)
- Support Middleware dependency resolution with new keys
:requires and :provides. Values are set of top-level keys of the request. e.g.
InjectUserIntoRequestMiddleware requires #{:session} and provides #{:user}