Question

I’d like to remotely monitor the activity of my Java EE application (deployed on a glassfish server).
Basically, I want my client-side implemented using Vaadin to display logs about the server-side activity.

The user would like to know what’s happening on the server side…These logs should only be high-level informative messages

I guess it really depends on the logging framework used if any. I’ve seen Chainsaw for log4j but this is a client on its own.
Otherwise, I could remotely read a file line by line (like tail -f)…but I don’t know how to do that either.

What’s the best solution to achieve this kind of thing?

Answer 1

In general what you could do is simply use a Vaadin Label, read a log file infinitely (or rather until stopped) and append the file content to the label. Here is code for a for that does exactly this:

      Thread t = new Thread() {
        @Override
        public void run() {

            BufferedReader reader = null;
            try {
                reader = new BufferedReader(new FileReader(LOGFILE));
                String line;
                while (running) {
                    line = reader.readLine();
                    if (line == null) {
                        // wait until there is more lines in the file
                        Thread.sleep(POLL_MS);
                    } else {
                        // append to the log Label
                        synchronized (MyApplication.this) {
                            log.setValue(log.getValue() + line + "<br />");
                        }
                    }
                }
            } catch (IOException e) {
                // TODO: handle me
                e.printStackTrace();
            } catch (InterruptedException e) {
                // TODO: handle me
                e.printStackTrace();
            } finally {
                running = false;
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (IOException ignore) {
                    }
                }
            }

        }
    };
    t.start();

For this to work you need a “RAW” mode Label and a ProgressIndicator that polls the server:

    ProgressIndicator pi = new ProgressIndicator();
    pi.setPollingInterval(POLL_MS);
    pi.setIndeterminate(true);
    layout.addComponent(pi);

Disclaimer: this code was from a non-critical application and for example error handling and HTML escaping is missing.