19.3.2 Defining Routes and Handlers

Crafting Robust APIs with Clojure Routing

Understanding Routing and Handlers in Clojure

In a full-stack application, defining clear and efficient API routes is pivotal. Clojure offers powerful libraries like Compojure and Pedestal to help manage routing, allowing us to define endpoints, route requests, and connect them with handlers that execute necessary operations.

Setting Up Routing with Compojure

Compojure is a popular routing library in Clojure, known for its simplicity and expressiveness. Here’s how you can set up basic routes:

(ns myapp.routes
  (:require [compojure.core :refer :all]
            [compojure.route :as route]))

(defroutes app-routes
  (GET "/" [] "Welcome to the API")
  (GET "/resource/:id" [id] (get-resource-handler id))
  (POST "/resource" request (create-resource-handler request))
  (PUT "/resource/:id" [id request] (update-resource-handler id request))
  (DELETE "/resource/:id" [id] (delete-resource-handler id))
  (route/not-found "Page not found"))

Defining Handlers

Handlers are functions that process incoming requests. Below are examples of handlers for typical CRUD operations:

(defn get-resource-handler [id]
  ;; Logic to retrieve a resource by ID
  "Resource details for given ID")

(defn create-resource-handler [request]
  ;; Logic to create a new resource
  "Resource created")

(defn update-resource-handler [id request]
  ;; Logic to update existing resource
  (str "Resource " id " updated"))

(defn delete-resource-handler [id]
  ;; Logic to delete a resource
  (str "Resource " id " deleted"))

Routing with Pedestal

Pedestal provides more elaborate routing capabilities suitable for highly scalable applications. Here’s a basic route configuration:

(require '[io.pedestal.http :as http])

(def routes
  #{["/" :get `home-page]
    ["/resource/:id" :get `get-resource-handler]
    ["/resource" :post `create-resource-handler]
    ["/resource/:id" :put `update-resource-handler]
    ["/resource/:id" :delete `delete-resource-handler]})
    
(http/create-server routes)

Best Practices for Organizing Routes and Handlers

1. Grouping Related Routes: Organize routes by their functionalities for better readability.
2. Modular Handlers: Keep handler functions small and focused, ideally each should handle a single type of request.
3. Error Handling: Incorporate proper error and exception handling within handlers to maintain robustness.
4. Documentation: Comment your routes and handlers or use libraries for generating documentation to aid understanding and maintenance.

Leverage Clojure’s powerful libraries to create structured and maintainable web APIs by defining clear routes and handler logic.

Quiz: Demonstrate Your Understanding