How to use Java Websocket to implement real-time ECG display?

With the development of Internet technology, the transmission and display of real-time data are receiving more and more attention. In the medical industry, real-time ECG display is critical to monitoring patients' lives. In Java language, we can use Websocket technology to display real-time electrocardiogram. Next, this article will introduce how to use Java Websocket to display real-time electrocardiogram and give specific code examples.

1. What is Java Websocket

Websocket is a new type of network communication protocol that enables two-way communication between the client and the server. Compared with the HTTP protocol, the Websocket protocol can push data in real time and improve the real-time nature of data transmission. In the Java language, we can use the API in the javax.websocket package to implement Websocket communication.

2. The process of realizing real-time electrocardiogram display

(1) Create Websocket server side

We can create the Websocket server side by implementing the javax.websocket.Endpoint class. The specific code is as follows:

import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/heartBeat")
public class HeartBeatEndpoint {

}

In this Endpoint class, we use the @ServerEndpoint annotation to specify the server-side address. Here we set the server side address to "/heartBeat".

(2) Send real-time ECG data to the client

After creating the Websocket service on the server side, we need to send real-time ECG data to the client. In this example, we use simulated ECG data, but you can also modify the data sent yourself. The specific code is as follows:

private void sendHeartBeat(Session session, int count) {
        Random random = new Random();
        float[] data = new float[100];

        for (int i = 0; i < 100; i++) {
            data[i] = (float) (random.nextGaussian() * 0.1 + Math.sin(count * 0.1 + i * 0.1));
        }

        String json = "{"command":"heartbeat","data":" + Arrays.toString(data) + "}";

        try {
            session.getBasicRemote().sendText(json);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

In this method, we use the Random class to generate random data, and then send the data to the client in JSON format. The data format is:

{
    "command": "heartbeat",
    "data": [1.0, 2.0, 3.0, ..., 100.0]
}

(3) Create Websocket client

We can use JavaScript or other languages ​​to implement the Websocket client, here we use JavaScript. The specific code is as follows:

var ws = new WebSocket("ws://localhost:8080/heartBeat");

ws.onmessage = function(event) {
    var data = JSON.parse(event.data);
    var command = data.command;
    var data = data.data;

    if (command === "heartbeat") {
        // 展示实时心电图数据
        showHeartBeat(data);
    }
} 

In this code, we use the WebSocket class to create a connection and set the server-side address. Next, we use the onmessage event handler to receive data from the server side. When it is detected that the command is "heartbeat", we call the showHeartBeat method to display the data.

(4) Display real-time ECG data

Finally, we need to display the real-time ECG data. Here, we use the Chart.js library to display ECG data. The specific code is as follows:

function showHeartBeat(data) {
    // 去除第一个元素
    data.shift();

    var ctx = document.getElementById('heartBeatChart').getContext('2d');

    var chart = new Chart(ctx, {
        type: 'line',
        data: {
            labels: Array.apply(null, {length: data.length}).map(Number.call, Number),
            datasets: [{
                data: data,
                borderColor: 'rgba(255,99,132)',
                backgroundColor: 'rgba(255,99,132,0.5)',
                fill: false
            }]
        },
        options: {
            legend: false,
            tooltips: false
        }
    });
}

In this code, we create a Chart.js line chart and pass in the electrocardiogram data. Here, we set the Y-axis coordinate of the electrocardiogram as the heart rate value, the X-axis coordinate as time, and the time interval is 0.1 seconds. In the chart, we display the ECG data with red lines.

3. Complete code example

The following is a complete Java and JavaScript code example:

Java code:

import java.io.IOException;
import java.util.Arrays;
import java.util.Random;
import javax.websocket.Endpoint;
import javax.websocket.EndpointConfig;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/heartBeat")
public class HeartBeatEndpoint implements Endpoint {
    private Session session;
    private Timer timer;

    @Override
    public void onOpen(Session session, EndpointConfig config) {
        this.session = session;

        timer = new Timer();
        timer.scheduleAtFixedRate(new TimerTask() {
            int count = 0;
            @Override
            public void run() {
                sendHeartBeat(session, count++);
            }
        }, 0, 100);
    }

    @Override
    public void onClose(Session session, CloseReason reason) {
        timer.cancel();
    }

    @Override
    public void onError(Session session, Throwable throwable) {
        throwable.printStackTrace();
    }

    private void sendHeartBeat(Session session, int count) {
        Random random = new Random();
        float[] data = new float[100];

        for (int i = 0; i < 100; i++) {
            data[i] = (float) (random.nextGaussian() * 0.1 + Math.sin(count * 0.1 + i * 0.1));
        }

        String json = "{"command":"heartbeat","data":" + Arrays.toString(data) + "}";

        try {
            session.getBasicRemote().sendText(json);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

JavaScript code:

var ws = new WebSocket("ws://localhost:8080/heartBeat");

ws.onmessage = function(event) {
    var data = JSON.parse(event.data);
    var command = data.command;
    var data = data.data;

    if (command === "heartbeat") {
        // 展示实时心电图数据
        showHeartBeat(data);
    }
}

function showHeartBeat(data) {
    // 去除第一个元素
    data.shift();

    var ctx = document.getElementById('heartBeatChart').getContext('2d');

    var chart = new Chart(ctx, {
        type: 'line',
        data: {
            labels: Array.apply(null, {length: data.length}).map(Number.call, Number),
            datasets: [{
                data: data,
                borderColor: 'rgba(255,99,132)',
                backgroundColor: 'rgba(255,99,132,0.5)',
                fill: false
            }]
        },
        options: {
            legend: false,
            tooltips: false
        }
    });
}

4. Summary

This article introduces how to use Java Websocket to implement real-time electrocardiogram display, and gives specific code examples. With the popularization and continuous improvement of Websocket technology, we believe that the transmission and display of real-time data will become more convenient and efficient. Hope this article is helpful to everyone.

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