All this kind of instrumentalization can be achieved by using native JMX or using a modular project like Metrics. Metrics provides a powerful way to measure the behaviour of your critical components and reporting them to a variety of systems like, JConsole, System Console, Ganglia, Graphite, CSV, or making them available through a web server.

To install Metrics, we only have to add metrics dependency. In this example we are going to use Maven.

<dependencies>
    <dependency>
        <groupId>com.yammer.metrics</groupId>
        <artifactId>metrics-core</artifactId>
        <version>2.2.0</version>
    </dependency>
</dependencies>

Now it is time to add some metrics to our code. In Metrics we can use 6 types of metrics:

So let's write a really simple application (in fact it is a console application) which sends queries to Google Search system. We will measure the number of petitions, the number of characters sent to Google, the last word searched, and a timer for measuring the rate of sending a request and receiving a response.

The main class where Measures will be applied is called MetricsApplication and is the responsible of connecting to Google and sending the entered word.

public class MetricsApplication {

 

//Counter

private final Counter numberOfSendCharacters = Metrics.newCounter(MetricsApplication.class, "Total-Number-Of-Characters");

//Meter

private final Meter sendMessages = Metrics.newMeter(MetricsApplication.class, "Sent-Messages", "Send", TimeUnit.SECONDS);

//Timer

private final Timer responseTime = Metrics.newTimer(MetricsApplication.class, "Response-Time");

private LinkedList<String> historyOfQueries = new LinkedList<String>();

{

//Gauge

Metrics.newGauge(MetricsApplication.class, "lastQuery", new Gauge<String>() {

 

@Override

public String value() {

return historyOfQueries.getLast();

}

});

}

public void sendQuery(String message) throws FailingHttpStatusCodeException, MalformedURLException, IOException {

updateMetrics(message);

TimerContext timerContext = responseTime.time();

sendQueryToGoogle(message);

timerContext.stop();

}

 

private void sendQueryToGoogle(String message) throws FailingHttpStatusCodeException, MalformedURLException, IOException {

WebClient webClient = new WebClient();

HtmlPage currentPage = webClient.getPage("http://www.google.com/");

//Get the query input text

HtmlInput queryInput = currentPage.getElementByName("q");

queryInput.setValueAttribute(message);

//Submit the form by pressing the submit button

HtmlSubmitInput submitBtn = currentPage.getElementByName("btnG");

currentPage = submitBtn.click();

}

private void updateMetrics(String message) {

numberOfSendCharacters.inc(message.length());

sendMessages.mark();

historyOfQueries.addLast(message);

}

}