Java - Use usb4java to detect USB devices plug and unplug

Java要存取到OS上面USB device相關的資訊本身不支援，一種是透過JNI的方式，讓Java呼叫C來幫忙存取，而C現成的library可以想到知名的libusb。在這邊使用的usb4java就是基於libusb來開發，可以說是libusb for java的代表，目前也有列在libusb的github上! 可惜的是在2018年後就沒有再出新版本，但並不影響今日要實作的部分，因為只有用到list出目前電腦上有哪些連接的USB devices，來偵測當下有哪些裝置plug or unplug!
首先，請至usb4java github下載目前最新的v1.3.0版本，解壓縮後將
commons-lang3-3.8.1.jar
libusb4java-1.3.0-win32-x86-64.jar (在此以Windows環境開發)
usb4java-1.3.0.jar
等加入到build path內

再來說明程式碼的部分:
#UsbDevice.java
  2. import java.util.Objects;
  4. public class UsbDevice {
  5. 	private short vid;
  6. 	private short pid;
  7. 	private int bus;
  8. 	private int port;
  9. 	private int device;
  10. 	
  11. 	public UsbDevice(int bus, int port, int device, short vid, short pid){
  12. 		this.bus = bus;
  13. 		this.port = port;
  14. 		this.device = device;
  15. 		this.vid = vid;
  16. 		this.pid = pid;
  17. 	}
  18. 	
  19. 	public short getVid() {
  20. 		return vid;
  21. 	}
  22. 	
  23. 	public short getPid() {
  24. 		return pid;
  25. 	}
  27. 	public int getDevice() {
  28. 		return device;
  29. 	}
  31. 	public void setDevice(int device) {
  32. 		this.device = device;
  33. 	}
  35. 	public int getBus() {
  36. 		return bus;
  37. 	}
  39. 	public int getPort() {
  40. 		return port;
  41. 	}
  43. 	@Override
  44. 	public int hashCode() {
  45. 		return Objects.hash(bus, device, port);
  46. 	}
  48. 	@Override
  49. 	public boolean equals(Object obj) {
  50. 		if (this == obj)
  51. 			return true;
  52. 		if (obj == null)
  53. 			return false;
  54. 		if (getClass() != obj.getClass())
  55. 			return false;
  56. 		UsbDevice other = (UsbDevice) obj;
  57. 		return bus == other.bus && device == other.device && port == other.port;
  58. 	}
  60. 	@Override
  61. 	public String toString() {
  62. 		return "UsbDevice [vid=" + String.format("0x%04x", vid) + ", pid=" + String.format("0x%04x", pid) + ", bus=" + bus + ", port=" + port + ", device=" + device +"]";
  63. 	}
  64. }

定義存放USB device的Vendor ID、Product ID、bus number、port number及device address等資訊
從Vendor ID、Product ID可以得知是否為相同的USB裝置
從bus number、port number及device address可以得知插入的位置
這邊的equals是判斷哪些device被插入或移除

#UsbDeviceDetectService.java
  2. import java.util.ArrayList;
  3. import java.util.List;
  4. import java.util.Timer;
  5. import java.util.TimerTask;
  7. import org.usb4java.Context;
  8. import org.usb4java.Device;
  9. import org.usb4java.DeviceDescriptor;
  10. import org.usb4java.DeviceList;
  11. import org.usb4java.LibUsb;
  12. import org.usb4java.LibUsbException;
  14. public abstract class UsbDeviceDetectService {
  15. 	private boolean enabled = false;
  16. 	private Timer timer;
  17. 	private Context context = new Context();
  18. 	
  19. 	protected abstract void getConnectedDevices(List<UsbDevice> usbDeviceList);
  20. 	
  21. 	protected void addUsbServicesListener() {
  22. 		timer = new Timer();
  23. 		timer.schedule(new TimerTask(){
  24. 			@Override
  25. 			public void run() {
  26. 				DeviceList list = new DeviceList();
  27. 				List<UsbDevice> plugTemp = new ArrayList<>();
  28. 				
  29. 				int result = LibUsb.getDeviceList(context, list);
  30. 			    if (result < 0) {
  31. 			    	cancel();
  32. 			    	throw new LibUsbException("Unable to get device list", result);
  33. 			    }
  34. 			    // Iterate over all devices and scan for the right one
  35. 			    try {
  36. 			        for (Device device: list){
  37. 			            DeviceDescriptor descriptor = new DeviceDescriptor();
  38. 			            result = LibUsb.getDeviceDescriptor(device, descriptor);
  39. 			            if (result != LibUsb.SUCCESS) 
  40. 			            	throw new LibUsbException("Unable to read device descriptor", result);
  41. 			            
  42. 			            UsbDevice usbDevice = new UsbDevice(LibUsb.getBusNumber(device), LibUsb.getPortNumber(device), LibUsb.getDeviceAddress(device), 
  43. 			            		descriptor.idVendor(), descriptor.idProduct());
  44. 			            plugTemp.add(usbDevice);
  45. 			        }
  46. 			        getConnectedDevices(plugTemp);
  47. 			    } finally{
  48. 			        // Ensure the allocated device list is freed
  49. 			        LibUsb.freeDeviceList(list, true);
  50. 			    }
  51. 			}
  52. 		}, 0 , 3000);
  53. 	}
  54. 	
  55. 	public void removeUsbServicesListener() {
  56. 		LibUsb.exit(context);
  57. 		context = null;
  58. 		if(timer != null){
  59. 			timer.cancel();
  60. 			timer = null;
  61. 		}
  62. 	}
  63. 	
  64. 	public boolean isEnabled() {
  65. 		return this.enabled;
  66. 	}
  68. 	public void setEnabled(boolean enabled) {
  69. 		this.enabled = enabled;
  70. 		if (this.enabled) {
  71. 			int result = LibUsb.init(context);
  72. 			if (result != LibUsb.SUCCESS) 
  73. 				throw new LibUsbException("Unable to initialize libusb.", result);
  74. 			addUsbServicesListener();
  75. 		} else {
  76. 			removeUsbServicesListener();
  77. 		}
  78. 	}
  79. }

此抽象類別需定義getConnectedDevices method要做什麼處理，當下傳入的usbDeviceList為目前正連接著的USB device，用一個timer每3秒輪詢一次作為間隔，以此達到隨時detect是否有新插入或移除的裝置!

#Main.java
  2. import java.util.ArrayList;
  3. import java.util.List;
  4. import java.util.Scanner;
  6. public class Main {
  7. 	private List<UsbDevice> connectedLists = new ArrayList<>();
  8. 	public static void main(String[] args) {
  9. 		// TODO Auto-generated method stub
  10. 		new Main();
  11. 	}
  12. 	
  13. 	public Main() {
  14. 		UsbDeviceDetectService service = new UsbDeviceDetectService() {
  15. 			boolean firstDetected = true;
  16. 			
  17. 			@Override
  18. 			protected void getConnectedDevices(List<UsbDevice> usbDeviceList) {
  19. 				// TODO Auto-generated method stub
  20. 				for(UsbDevice device : usbDeviceList) {
  21. 					if(!connectedLists.contains(device)) {
  22. 						connectedLists.add(device);
  23. 						if(!firstDetected) {
  24. 							System.out.println(">> Plug: "+device);
  25. 						}
  26. 					}
  27. 				}
  28. 				
  29. 				firstDetected = false;
  30. 				
  31. 				if(connectedLists.size() > usbDeviceList.size()) {
  32. 					List<UsbDevice> unplugList = new ArrayList<>();
  33. 					for(UsbDevice device : connectedLists) {
  34. 						if(!usbDeviceList.contains(device)) {
  35. 							unplugList.add(device);
  36. 							System.out.println("<< Unplug: "+device);
  37. 						}
  38. 					}
  39. 					connectedLists.removeAll(unplugList);
  40. 				}
  41. 			}
  42. 		};
  43. 		
  44. 		Scanner input = new Scanner(System.in);
  45. 		try {
  46. 			while(true) {
  47. 				System.out.println("(1)Start USB Service(2)List Connected Devices(3)Terminate");
  48. 				int option = input.nextInt();
  49. 				if(option == 1) {
  50. 					if(!service.isEnabled()) {
  51. 						service.setEnabled(true);
  52. 						System.out.println("Start USB Detect Listener");
  53. 					}else {
  54. 						System.out.println("USB Detect has been started");
  55. 					}
  56. 				}else if(option == 2) {
  57. 					System.out.println("Connected Devices:");
  58. 					for(UsbDevice device : connectedLists) {
  59. 						System.out.println(device);
  60. 					}
  61. 				}else if(option == 3) {
  62. 					if(service.isEnabled()) {
  63. 						service.setEnabled(false);
  64. 						System.out.println("Terminate and remove USB Detect Listener");
  65. 						break;
  66. 					}else {
  67. 						System.out.println("Terminate");
  68. 					}
  69. 				}else {
  70. 					continue;
  71. 				}
  72. 				System.out.println();
  73. 			}
  74. 		} finally {
  75. 			input.close();
  76. 		}
  77. 	}
  78. }

主程式提供一操作，分別為啟動USB detect server及列出目前連接的裝置及終止程式運作
其覆寫的getConnectedDevices method內簡單判斷目前什麼裝置plug or unplug，並撇除了啟動USB detect時本身已插著的裝置

執行結果如下:

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