POST / Redirect / GET

When working with vanilla Deno, we learned the basic concepts of the POST/Redirect/GET pattern and learned to incorporate that into our web applications. Here's a quick quiz to refresh your memory.

Let us take a brief look into creating the POST/Redirect/GET pattern with the router. While previously, we have had to set the status code 303 and the 'Location' response header to the response, oak provides a ready-made method redirect that does the work for us.

The redirect method is a part of the response object. The method takes the path to which the request should be redirected as a parameter -- no status code or header needs to be set. The following example, which is a modification of the previously seen counter, shows how the POST/Redirect/GET -pattern works when using oak.

import { Application, Router } from "https://deno.land/x/oak@v12.6.1/mod.ts";

const app = new Application();

const router = new Router();

let count = 0;

const getCount = ({ response }) => {
  response.body = `${count}`;
};

const increaseCount = ({ response }) => {
  count++;
  response.redirect("/");
};

router.get("/", getCount)
  .post("/", increaseCount);

app.use(router.routes());

app.listen({ port: 7777 });

When we try out the application, we observe that the server responds to POST requests with appropriate redirect headers. While we previously used the status code 303, the server seems to use the status code 302. This works as well.

curl http://localhost:7777
0%
curl -v -X POST http://localhost:7777
// ...
< HTTP/1.1 302 Found
< content-length: 17
< location: /
< content-type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
Redirecting to /.%
curl -v -X POST http://localhost:7777
// ...
< HTTP/1.1 302 Found
< content-length: 17
< location: /
< content-type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
Redirecting to /.%
curl http://localhost:7777
2%

When we study the responses to the requests we observe that, in addition to the correct headers, the server also responds with a textual message telling what is happening. The message Redirecting to /. can be useful, for example, if the browser does not automatically follow redirect responses.