9.2.2 Functions as CLI Applications

To execute your function as a CLI application with java -jar, you will need to package your application as an executable JAR file. For example, in build.gradle:

build.gradle

buildscript {
    repositories {
        maven { url "https://plugins.gradle.org/m2/" } (1)
    }
    dependencies {
        classpath "com.github.jengelman.gradle.plugins:shadow:2.0.4"
...
    }
}
apply plugin:"com.github.johnrengelman.shadow"
shadowJar {
    mergeServiceFiles()
}

You can now package your application using the shadowJar task.

Packaging a Function as a JAR

$ ./gradlew shadowJar

At this point, you can execute your function using the java -jar command. To supply input data to the function, simply pipe input via System.in. For example:

Executing a function via the CLI

$ echo '{value: 3}' | java -jar build/libs/math-function-0.1-all.jar

The above example will provide the JSON {value: 3} to function which will write the return value to standard out.

This allows functions written with Micronaut to be deployed to Function-as-a-Service (FaaS) platforms that process functions via standard in/out such as OpenFaaS.