Play Framework/Scala example source code file (Comet.java)

This example Play Framework source code file (Comet.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Play Framework (and Scala) source code examples by using tags.

All credit for the original source code belongs to Play Framework; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Play Framework tags/keywords

callback, chunks, comet, exception, lib, library, nullpointerexception, override, play, play framework, string, throwable, whenconnectedcomet

The Comet.java Play Framework example source code

/*
 * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
 */
package play.libs;

import play.mvc.Results.*;

import play.libs.F.*;

import com.fasterxml.jackson.databind.JsonNode;

import java.util.*;

/**
 * A Chunked stream sending Comet messages.
 */
public abstract class Comet extends Chunks<String> {

    private Chunks.Out<String> out;
    private String callbackMethod;

    /**
     * Create a new Comet socket
     *
     * @param callbackMethod The Javascript callback method to call on each message.
     */
    public Comet(String callbackMethod) {
        super(play.core.j.JavaResults.writeString("text/html", play.api.mvc.Codec.javaSupported("utf-8")));
        this.callbackMethod = callbackMethod;
    }

    public void onReady(Chunks.Out<String> out) {
        this.out = out;
        out.write(initialBuffer());
        onConnected();
    }

    /**
     * Initial chunk of data to send for browser compatibility (default to send 5Kb of blank data).
     */
    protected String initialBuffer() {
        char[] buffer = new char[1024 * 5];
        Arrays.fill(buffer, ' ');
        return new String(buffer);
    }

    /**
     * Send a message on this socket (will be received as String in the Javascript callback method).
     */
    public void sendMessage(String message) {
        out.write("<script type=\"text/javascript\">" + callbackMethod + "('" + org.apache.commons.lang3.StringEscapeUtils.escapeEcmaScript(message) + "');</script>");
    }

    /**
     * Send a Json message on this socket (will be received as Json in the Javascript callback method).
     */
    public void sendMessage(JsonNode message) {
        out.write("<script type=\"text/javascript\">" + callbackMethod + "(" + Json.stringify(message) + ");</script>");
    }

    /**
     * The socket is ready, you can start sending messages.
     */
    public abstract void onConnected();

    /**
     * Add a callback to be notified when the client has disconnected.
     */
    public void onDisconnected(Callback0 callback) {
        out.onDisconnected(callback);
    }

    /**
     * Close the channel
     */
    public void close() {
        out.close();
    }

    /**
     * Creates a Comet. The abstract {@code onConnected} method is
     * implemented using the specified {@code Callback<Comet>} and
     * is invoked with {@code Comet.this}.
     *
     * @param jsMethod the Javascript method to call on each message
     * @param callback the callback used to implement onConnected
     * @return a new Comet
     * @throws NullPointerException if the specified callback is null
     */
    public static Comet whenConnected(String jsMethod, Callback<Comet> callback) {
        return new WhenConnectedComet(jsMethod, callback);
    }

    /**
     * An extension of Comet that obtains its onConnected from
     * the specified {@code Callback<Comet>}.
     */
    static final class WhenConnectedComet extends Comet {

        private final Callback<Comet> callback;

        WhenConnectedComet(String jsMethod, Callback<Comet> callback) {
            super(jsMethod);
            if (callback == null) throw new NullPointerException("Comet onConnected callback cannot be null");
            this.callback = callback;
        }

        @Override
        public void onConnected() {
            try {
                callback.invoke(this);
            } catch (Throwable e) {
                play.PlayInternal.logger().error("Exception in Comet.onConnected", e);
            }
        }
    }

}