Compojure

Routes

Routes are a type of handler that return nil if the request does not match certain criteria.

For example, the route function below will only return a response if URI is "/":

(defn hello-route [request]
  (if (= (:uri request) "/")
    {:status  200
     :headers {}
     :body    "Hello World"}))

This example demonstrates a basic, but verbose way of defining a route. A more concise method is to use route macros.

Routes are useful because they can be chained in sequence. If a route in the sequence returns nil, the request is passed to the next route. This continues until a valid response is returned, or the list of routes is exhaused.

Routes can be chained in this fashion using the routes function. Compojure also supplies a defroutes macro to simplify the process of defining route chains.

In the example below, three route functions are combined to make a single handler function:

(defroutes my-handler
  hello-route
  some-other-route
  404-route)