Firstly, we initialize our function by creating a func.yaml using fn init. This command can optionally take a --runtime flag to explicitly specify the target function runtime. In this example, the target runtime is implied to be Java because there is a Func.java file in the working directory.

$ fn init <YOUR_DOCKERHUB_USERNAME>/hello-java

This is what our func.yaml looks like now.

name: mhaji/hello-java
version: 0.0.1
runtime: java
entrypoint: java Func
path: /hello-java
max_concurrency: 1

Next, we build and run our function using fn run.

$ fn run
Hello, world!

You can also pipe input via stdin into to the function as follows:

$ echo "Michael FassBender" | fn run
Hello Michael FassBender!

To execute your function via a HTTP trigger:

fn apps create myapp
fn routes create myapp /hello
curl -H "Content-Type: text/plain" -X POST -d "Michael FassBender" http://localhost:8080/r/myapp/hello