actions-ballerina.md

Creating and invoking Ballerina actions

The process of creating Ballerina actions is similar to that of other actions. The following sections guide you through creating and invoking a Ballerina action.

Ballerina actions are executed using Ballerina 0.990.2. You will need a compatible version of the compiler locally available to generate the executable. Without the Ballerina compiler, you cannot create an OpenWhisk action.

An action is simply a top-level Ballerina function which accepts and returns a JSON object. For example, create a file called hello.bal with the following source code:

import ballerina/io;

public function main(json data) returns json {
  json? name = data.name;
  if (name == null) {
    return { greeting: "Hello stranger!" };
  } else {
    return { greeting: "Hello " + name.toString() + "!" };
  }
}

The entry method for the action is main by default but may be specified explicitly when creating the action with the wsk CLI using --main, as with any other action type. It is important to note that the Ballerina compiler expects the presence of a function called main to generate the executable. Hence, when using alternate entry points, your source file must still include a place holder called main.

You can create an OpenWhisk action called bello from the function above as follows:

# generate the .balx file first
ballerina build hello.bal

# use the .balx file to create the action
wsk action create bello hello.balx --kind ballerina:0.990

The CLI does not yet automatically infer the type of the action from the source file extension. So you must specify the kind explicitly. For .balx source files, the action currently runs using the Ballerina 0.990.2 runtime.

Action invocation is the same for Ballerina actions as it is for any other action.

wsk action invoke --result bello --param name World

{
  "greeting": "Hello World!"
}

Find out more about parameters in the Working with parameters section.