Javaweb读取串口电子秤的数据

要在Java Web应用程序中读取串口电子秤的数据，需要使用Java串口通信库（如RXTX或jSerialComm）和一些基本的Java Web编程概念。下面是一个简单的实例代码片段，用于读取串口电子秤的数据并在Web页面上显示：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Enumeration;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import gnu.io.CommPort;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;

public class ScaleServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        try {
            // Set response content type
            response.setContentType("text/html");

            // Get available serial ports
            Enumeration<?> portIdentifiers = CommPortIdentifier.getPortIdentifiers();

            // Find the port with the scale connected
            CommPortIdentifier scalePortIdentifier = null;
            while (portIdentifiers.hasMoreElements()) {
                CommPortIdentifier portIdentifier = (CommPortIdentifier) portIdentifiers.nextElement();
                if (portIdentifier.getPortType() == CommPortIdentifier.PORT_SERIAL) {
                    SerialPort serialPort = null;
                    try {
                        serialPort = (SerialPort) portIdentifier.open("ScaleServlet", 2000);
                        BufferedReader input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
                        String line = input.readLine();
                        if (line.contains("SCALE")) {
                            scalePortIdentifier = portIdentifier;
                            break;
                        }
                    } catch (Exception e) {
                        // Ignore and continue searching
                    } finally {
                        if (serialPort != null) {
                            serialPort.close();
                        }
                    }
                }
            }

            // Read scale data from the selected port
            if (scalePortIdentifier != null) {
                SerialPort scalePort = (SerialPort) scalePortIdentifier.open("ScaleServlet", 2000);
                BufferedReader input = new BufferedReader(new InputStreamReader(scalePort.getInputStream()));
                String line = input.readLine();
                String weight = line.substring(line.indexOf("=") + 1, line.indexOf("g"));
                input.close();
                scalePort.close();

                // Write scale data to response
                response.getWriter().println("<h1>Scale weight: " + weight + "g</h1>");
            } else {
                response.getWriter().println("<h1>No scale found!</h1>");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

请注意，这只是一个简单的示例，并且可能需要根据您的具体需求进行更改。另外，如果您使用的是jSerialComm库，需要将引用从gnu.io.SerialPort改为com.fazecast.jSerialComm.SerialPort。