linux 用Java监听插入u盘

要在Linux上使用Java监听插入U盘，可以使用Java的JNA库来实现。

以下是实现的步骤：

1. 安装JNA库

可以使用Maven或Gradle等构建工具来安装JNA库。

Maven：

<dependency>
    <groupId>net.java.dev.jna</groupId>
    <artifactId>jna</artifactId>
    <version>5.2.0</version>
</dependency>

Gradle：

implementation 'net.java.dev.jna:jna:5.2.0'

2. 编写代码

使用JNA库可以调用Linux系统的udev库，监听USB设备的插入和拔出。

代码如下：

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.ptr.PointerByReference;

import java.util.Arrays;
import java.util.List;

public class USBListener {

    public interface UdevLibrary extends Library {
        UdevLibrary INSTANCE = Native.load("udev", UdevLibrary.class);

        Pointer udev_new();

        void udev_unref(Pointer udev);

        Pointer udev_monitor_new_from_netlink(Pointer udev, String name);

        void udev_monitor_enable_receiving(Pointer udev_monitor);

        int udev_monitor_get_fd(Pointer udev_monitor);

        Pointer udev_monitor_receive_device(Pointer udev_monitor);

        String udev_device_get_devnode(Pointer udev_device);

        String udev_device_get_property_value(Pointer udev_device, String key);

        String udev_device_get_subsystem(Pointer udev_device);

        String udev_device_get_action(Pointer udev_device);

        void udev_device_unref(Pointer udev_device);
    }

    public static void main(String[] args) {
        Pointer udev = UdevLibrary.INSTANCE.udev_new();
        if (udev == null) {
            System.err.println("Failed to initialize udev");
            System.exit(1);
        }

        Pointer udev_monitor = UdevLibrary.INSTANCE.udev_monitor_new_from_netlink(udev, "udev");
        if (udev_monitor == null) {
            System.err.println("Failed to initialize udev monitor");
            System.exit(1);
        }

        UdevLibrary.INSTANCE.udev_monitor_enable_receiving(udev_monitor);
        int fd = UdevLibrary.INSTANCE.udev_monitor_get_fd(udev_monitor);

        while (true) {
            PointerByReference udev_device_ref = new PointerByReference();
            int result = Native.poll(new NativePollFd[]{new NativePollFd(fd, (short) Native.POLLIN, (short) 0)}, -1);
            if (result > 0) {
                Pointer udev_device = UdevLibrary.INSTANCE.udev_monitor_receive_device(udev_monitor);
                if (udev_device != null) {
                    String subsystem = UdevLibrary.INSTANCE.udev_device_get_subsystem(udev_device);
                    String action = UdevLibrary.INSTANCE.udev_device_get_action(udev_device);
                    if ("block".equals(subsystem) && "add".equals(action)) {
                        String devnode = UdevLibrary.INSTANCE.udev_device_get_devnode(udev_device);
                        String vendorId = UdevLibrary.INSTANCE.udev_device_get_property_value(udev_device, "ID_VENDOR_ID");
                        String productId = UdevLibrary.INSTANCE.udev_device_get_property_value(udev_device, "ID_MODEL_ID");
                        System.out.println("USB device inserted: " + devnode + " (" + vendorId + ":" + productId + ")");
                    }
                    UdevLibrary.INSTANCE.udev_device_unref(udev_device);
                }
            }
        }
    }

    public static class NativePollFd extends Structure {
        public int fd;
        public short events;
        public short revents;

        public NativePollFd() {
            super();
        }

        public NativePollFd(int fd, short events, short revents) {
            super();
            this.fd = fd;
            this.events = events;
            this.revents = revents;
        }

        @Override
        protected List<String> getFieldOrder() {
            return Arrays.asList("fd", "events", "revents");
        }
    }
}

该代码使用了poll系统调用来监听udev监视器的文件描述符。当有USB设备插入时，会从udev监视器中接收到一个udev设备对象，并从中获取设备节点、厂商ID和产品ID等信息。

3. 运行代码

可以使用命令行编译并运行代码：

javac -cp .:jna-5.2.0.jar USBListener.java
java -cp .:jna-5.2.0.jar USBListener

运行后，插入U盘时将会输出类似以下的信息：

USB device inserted: /dev/sdb1 (0951:1625)

注意：要运行此代码需要使用root权限或者在udev规则中添加相应的权限