An AWS Lambda that generates a QR code for a URL. This code uses the ZXing library that, while officially in maintenance mode, is still updated and works.

To build, simply run

mvn clean package

This will create target/qr-code-lambda-1.0.jar that can be deployed to AWS Lambda via the console or CLI. Note that this code does not include any deployment mechanisms - that's up to you.

The code exposes a single "service" that is used to request a QR code. The request is a simple JSON body:

 {
     "url": "https%3A%2F%2Fwww.blah.com%2F%3Fparam1%3Dblech%26param2%3Dboo", 
     "size": 200
 }

Note that the URL is expected to be URL encoded. This prevents anything that might be in the URL from being interpreted as valid JSON.

The size parameter is optional. By default, the code returns a QR code that is 200 x 200 pixels. You can override this in the deployment environment by setting the environment variable DEFAULT_SIZE in the Lambda runtime environment. The value in the JSON takes precedence over either the default or the environment variable.

The code limits you to between 50 and 1000 pixels for the QR code. Anything outside of this range returns a 400 error.

A image/png is returned inside a APIGatewayProxyResponseEvent so that API Gateway can convert the returned data to an image.

This code doesn't require much memory and will trivially run in the default 15 second Lambda timeout. Because it is Java based I'd encourage you to use SnapStart. In my testing this code takes about 700ms to run the first time and, without SnapStart, can periodically still take that amount of time. With SnapStart it is usually around 7 to 10ms.

There is no security built into this Lambda. I've deployed behind an API Gateway with a JWT authorizer, but it should not be put out for the world without some kind of protection.

Note that, depending on the length of your URL, the returned QR code can be fairly simple or extremely dense. For example, a simple request that has the URL of https://www.google.com/ looks like this:

However, a URL that is large (this one is a bit over 2000 characters) can result in a QR code like:

While the first QR code is easily read at 200 x 200 px, the second one may not be, depending on the screen and resolution that it is displayed with. If you have very long URL's, consider a link shortening service to create the QR code so that it is easily readable across devices.