How to serve images using deno's oak?

Question

Deno seems targeting text files, but I also need to serve image files for the website.

Answer 1

You can use send()

The function send() is designed to serve static content as part of a middleware function. In the most straight forward usage, a root is provided and requests provided to the function are fulfilled with files from the local file system relative to the root from the requested path.

const app = new Application();

app.use(async (context) => {
   await send(context, context.request.url.pathname, {
      root: `${Deno.cwd()}/static`
   });
});

await app.listen({ port: 8000 });

With the following directory structure:

static/
   image.jpg
server.js

You can access the image by going to http://localhost:8000/image.jpg

Answer 2

Basically, you just need to set the correct headers for your image type, and supply the image data as a Unit8Array:

In your middleware:

app.use(async (ctx, next) => {
  // ...
  const imageBuf = await Deno.readFile(pngFilePath);
  ctx.response.body = imageBuf;
  ctx.response.headers.set('Content-Type', 'image/png');
});

Here's a complete working example, which will download a sample image (the digitized version of the hand-drawn deno logo) and serve it at http://localhost:8000/image, and display "Hello world" at all other addresses. The run options are in the comment on the first line:

server.ts

// deno run --allow-net=localhost:8000,deno.land --allow-read=deno_logo.png --allow-write=deno_logo.png server.ts

import {Application} from 'https://deno.land/x/oak@v5.3.1/mod.ts';
import {exists} from 'https://deno.land/std@0.59.0/fs/exists.ts';

// server listen options
const listenOptions = {
  hostname: 'localhost',
  port: 8000,
};

// sample image
const imageFilePath = './deno_logo.png';
const imageSource = 'https://deno.land/images/deno_logo.png';

const ensureLocalFile = async (localPath: string, url: string): Promise<void> => {
  const fileExists = await exists(localPath);
  if (fileExists) return;
  console.log(`Downloading ${url} to ${localPath}`);
  const response = await fetch(url);
  if (!response.ok) throw new Error('Response not OK');
  const r = response.body?.getReader;
  const buf = new Uint8Array(await response.arrayBuffer());
  await Deno.writeFile(imageFilePath, buf);
  console.log('File saved');
};

await ensureLocalFile(imageFilePath, imageSource);

const app = new Application();

app.use(async (ctx, next) => {
  // only match /image
  if (ctx.request.url.pathname !== '/image') {
    await next(); // pass control to next middleware
    return;
  }

  const imageBuf = await Deno.readFile(imageFilePath);
  ctx.response.body = imageBuf;
  ctx.response.headers.set('Content-Type', 'image/png');
});

// default middleware
app.use((ctx) => {
  ctx.response.body = "Hello world";
});

// log info about server
app.addEventListener('listen', ev => {
  const defaultPortHttp = 80;
  const defaultPortHttps = 443;
  let portString = `:${ev.port}`;

  if (
    (ev.secure && ev.port === defaultPortHttps)
    || (!ev.secure && ev.port === defaultPortHttp)
  ) portString = '';

  console.log(`Listening at http${ev.secure ? 's' : ''}://${ev.hostname ?? '0.0.0.0'}${portString}`);
  console.log('Use ctrl+c to stop\n');
});

await app.listen(listenOptions);

Answer 3

Register middleware like this:

// serve static files
app.use(async (context, next) => {
  try {
    await context.send({
      root: `${Deno.cwd()}/wwwroot/static`,
      index: "index.html",
    });
  } catch {
    await next();
  }
});