Run a MicroProfile application as a serverless function with CloudEvents in IBM Cloud Code Engine

// tag::copyright[]
/*******************************************************************************
 * Copyright (c) 2017, 2022 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - Initial implementation
 *******************************************************************************/
// end::copyright[]
package io.openliberty.sample.system;

import io.cloudevents.CloudEvent;
import io.cloudevents.CloudEventData;
import io.cloudevents.core.builder.CloudEventBuilder;
import jakarta.json.bind.Jsonb;
import jakarta.json.bind.JsonbBuilder;
import jakarta.ws.rs.POST;

import jakarta.enterprise.context.RequestScoped;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;

import org.eclipse.microprofile.metrics.annotation.Counted;
import org.eclipse.microprofile.metrics.annotation.Timed;

import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

@RequestScoped
@Path("/properties")
public class SystemResource {

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @Timed(name = "getPropertiesTime",
           description = "Time needed to get the JVM system properties")
    @Counted(absolute = true, description
             = "Number of times the JVM system properties are requested")
    public CloudEvent getProperties() {
        /* java.util.properties does not have a direct way to obtain a byte[] so store in an intermedietary Map first*/
        Map properties = System.getProperties();
        Jsonb jsonb = JsonbBuilder.create();
        /* convert properties map into a JSON string which can then be converted into a byte[]*/
        String jsonString = jsonb.toJson(properties);
        return CloudEventBuilder.v1()
                .withData(jsonString.getBytes())
                .withDataContentType("application/json")
                .withId("properties")
                .withType("java.properties")
                .withSource(URI.create("http://system.poperties"))
                .build();
    }

    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Timed(name = "queryPropertiesTime",
            description = "Time needed to query the JVM system properties")
    @Counted(absolute = true, description
            = "Number of times the JVM system properties are queried")
    public CloudEvent queryProperties(CloudEvent query){
        Map properties = System.getProperties();
        HashMap<String,String> props = new HashMap<>((Map<String,String>)properties);
        HashMap<String,String> qProps = new HashMap<String,String>();
        Jsonb jsonb = JsonbBuilder.create();

        /* Pull data from the data portion of the CloudEvent - this is in binary format so convert it into a standard String*/
        CloudEventData data = query.getData();
        String jsonString = new String(data.toBytes(), StandardCharsets.UTF_8);

        /* Take the Json Array data and use that to pull out the request properties */
        ArrayList<String> tProps = jsonb.fromJson(jsonString, ArrayList.class);
        for(String key: tProps){
            qProps.put(key, props.get(key));
        }

        /* return a CloudEvent with our queried properties */
        return CloudEventBuilder.v1()
                .withData(jsonb.toJson(qProps).getBytes())
                .withDataContentType("application/json")
                .withId("properties")
                .withType("java.properties")
                .withSource(URI.create("http://system.poperties"))
                .build();
    }

}

public CloudEvent getProperties() {

/* java.util.properties does not have a direct way to obtain a byte[] so store in an intermediary Map first*/
    Map properties = System.getProperties();
    Jsonb jsonb = JsonbBuilder.create();
/* convert properties map into a JSON string which can then be converted into a byte[]*/
    String jsonString = jsonb.toJson(properties);

    return CloudEventBuilder.v1()
        .withData(jsonString.getBytes())
        .withDataContentType("application/json")
        .withId("properties")
        .withType("java.properties")
        .withSource(URI.create("http://system.poperties"))
        .build();

["java.vendor.url","awt.toolkit"]

    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Timed(name = "queryPropertiesTime",
            description = "Time needed to query the JVM system properties")
    @Counted(absolute = true, description
            = "Number of times the JVM system properties are queried")
    public CloudEvent queryProperties(CloudEvent query){


}

Map properties = System.getProperties();
HashMap<String,String> props = new HashMap<>((Map<String,String>)properties);
HashMap<String,String> qProps = new HashMap<String,String>();
Jsonb jsonb = JsonbBuilder.create();

/* Pull data from the data portion of the CloudEvent - this is in binary format so convert it into a standard String*/
CloudEventData data = query.getData();
String jsonString = new String(data.toBytes(), StandardCharsets.UTF_8);

/* Take the Json Array data and use that to pull out the request properties */
ArrayList<String> tProps = jsonb.fromJson(jsonString, ArrayList.class);
for(String key: tProps){
    qProps.put(key, props.get(key));
}

return CloudEventBuilder.v1()
    .withData(jsonb.toJson(qProps).getBytes())
    .withDataContentType("application/json")
    .withId("properties")
    .withType("java.properties")
    .withSource(URI.create("http://system.poperties"))
    .build();

curl -X POST http://${ICCE_Application_URL}/dev/system/properties \
-H "Ce-Specversion: 1.0" \
-H "Ce-Type: properties" \
-H "Ce-Source: io.cloudevents.examples/properties" \
-H "Ce-Id: 536808d3-88be-4077-9d7a-a3f162705f78" \
-H "Content-Type: application/json" \
-H "Ce-Subject: resources" \
-d "[\"java.vendor.url\",\"awt.toolkit\"]"