SseOutput.java

package io.fabric8.launcher.web.endpoints;

import java.io.IOException;
import java.io.PrintWriter;

import javax.annotation.PostConstruct;
import javax.enterprise.context.RequestScoped;
import javax.enterprise.event.Observes;
import javax.inject.Inject;
import javax.json.Json;
import javax.json.JsonArrayBuilder;
import javax.json.JsonObjectBuilder;
import javax.servlet.http.HttpServletResponse;

import com.fasterxml.jackson.databind.ObjectMapper;
import io.fabric8.launcher.core.api.events.StatusEventType;
import io.fabric8.launcher.core.api.events.StatusMessageEvent;

/**
 * @author <a href="mailto:[email protected]">George Gastaldi</a>
 */
@RequestScoped
public class SseOutput {

    @Inject
    HttpServletResponse response;

    private static final ObjectMapper objectMapper = new ObjectMapper();


    @PostConstruct
    public void initialize() throws IOException {
        JsonArrayBuilder builder = Json.createArrayBuilder();
        for (StatusEventType statusEventType : StatusEventType.values()) {
            JsonObjectBuilder object = Json.createObjectBuilder();
            builder.add(object.add(statusEventType.name(), statusEventType.getMessage()).build());
        }
        String payload = builder.build().toString();
        send(payload);
    }

    private void send(String payload) throws IOException {
        PrintWriter writer = response.getWriter();
        writer.write(payload + "\n\n");
        writer.flush();
    }


    /**
     * Listen to status changes and pushes them to the registered sessions
     *
     * @param msg the status message to be send
     * @throws IOException when message could not be serialized to JSON
     */
    public void onEvent(@Observes StatusMessageEvent msg) throws IOException {
        String message = objectMapper.writeValueAsString(msg);
        send(message);
    }

}