Use of "USB4JAVA.jar" to get information about attached devices in linux

Question

I google about getting information of USB attached to linux OS and found that USB4JAVA is very helpful to do the same. I found sample code as below. Now after running it i got Exception of "java.lang.ExceptionInInitializerError".

Code that i used :

import org.usb4java.ConfigDescriptor;
import org.usb4java.Context;
import org.usb4java.DescriptorUtils;
import org.usb4java.Device;
import org.usb4java.DeviceDescriptor;
import org.usb4java.DeviceHandle;
import org.usb4java.DeviceList;
import org.usb4java.LibUsb;
import org.usb4java.LibUsbException;
/**
* Dumps the descriptors of all available devices.
*
* @author Klaus Reimer <[email protected]>
*/
public class DumpDevices
{
    /**
    * Dumps all configuration descriptors of the specified device. Because
    * libusb descriptors are connected to each other (Configuration descriptor
    * references interface descriptors which reference endpoint descriptors)
    * dumping a configuration descriptor also dumps all interface and endpoint
    * descriptors in this configuration.
    *
    * @param device
    * The USB device.
    * @param numConfigurations
    * The number of configurations to dump (Read from the device
    * descriptor)
    */
    public static void dumpConfigurationDescriptors(final Device device,
    final int numConfigurations)
    {
        for (byte i = 0; i < numConfigurations; i += 1)
        {
            final ConfigDescriptor descriptor = new ConfigDescriptor();
            final int result = LibUsb.getConfigDescriptor(device, i, descriptor);
            if (result < 0)
            {
                throw new LibUsbException("Unable to read config descriptor",
                result);
            }
            try
            {
                System.out.println(descriptor.dump().replaceAll("(?m)^",
                " "));
            }
            finally
            {
                // Ensure that the config descriptor is freed
                LibUsb.freeConfigDescriptor(descriptor);
            }
        }
    }
    /**
    * Dumps the specified device to stdout.
    *
    * @param device
    * The device to dump.
    */
    public static void dumpDevice(final Device device)
    {
        // Dump device address and bus number
        final int address = LibUsb.getDeviceAddress(device);
        final int busNumber = LibUsb.getBusNumber(device);
        System.out.println(String
        .format("Device %03d/%03d", busNumber, address));
        // Dump port number if available
        final int portNumber = LibUsb.getPortNumber(device);
        if (portNumber != 0)
            System.out.println("Connected to port: " + portNumber);
        // Dump parent device if available
        final Device parent = LibUsb.getParent(device);
        if (parent != null)
        {
            final int parentAddress = LibUsb.getDeviceAddress(parent);
            final int parentBusNumber = LibUsb.getBusNumber(parent);
            System.out.println(String.format("Parent: %03d/%03d",
            parentBusNumber, parentAddress));
        }
        // Dump the device speed
        System.out.println("Speed: "
        + DescriptorUtils.getSpeedName(LibUsb.getDeviceSpeed(device)));
        // Read the device descriptor
        final DeviceDescriptor descriptor = new DeviceDescriptor();
        int result = LibUsb.getDeviceDescriptor(device, descriptor);
        if (result < 0)
        {
            throw new LibUsbException("Unable to read device descriptor",
            result);
        }
        // Try to open the device. This may fail because user has no
        // permission to communicate with the device. This is not
        // important for the dumps, we are just not able to resolve string
        // descriptor numbers to strings in the descriptor dumps.
        DeviceHandle handle = new DeviceHandle();
        result = LibUsb.open(device, handle);
        if (result < 0)
        {
            System.out.println(String.format("Unable to open device: %s. "
            + "Continuing without device handle.",
            LibUsb.strError(result)));
            handle = null;
        }
        // Dump the device descriptor
        System.out.print(descriptor.dump(handle));
        // Dump all configuration descriptors
        dumpConfigurationDescriptors(device, descriptor.bNumConfigurations());
        // Close the device if it was opened
        if (handle != null)
        {
            LibUsb.close(handle);
        }
    }
    /**
    * Main method.
    *
    * @param args
    * Command-line arguments (Ignored)
    */
    public static void main(final String[] args)
    {
        // Create the libusb context
        final Context context = new Context();
        // Initialize the libusb context
        int result = LibUsb.init(context);
        if (result < 0)
        {
            throw new LibUsbException("Unable to initialize libusb", result);
        }
        // Read the USB device list
        final DeviceList list = new DeviceList();
        result = LibUsb.getDeviceList(context, list);
        if (result < 0)
        {
            throw new LibUsbException("Unable to get device list", result);
        }
        try
        {
            // Iterate over all devices and dump them
            for (Device device: list)
            {
                dumpDevice(device);
            }
        }
        finally
        {
            // Ensure the allocated device list is freed
            LibUsb.freeDeviceList(list, true);
        }
        // Deinitialize the libusb context
        LibUsb.exit(context);
    }
}

Exception that i got :

Exception in thread "main" java.lang.ExceptionInInitializerError
    at find_usb.DumpDevices.main(DumpDevices.java:132)
Caused by: org.usb4java.LoaderException: Native library not found in classpath: /org/usb4java/linux-x86/libusb4java.so
    at org.usb4java.Loader.extractLibrary(Loader.java:281)
    at org.usb4java.Loader.load(Loader.java:358)
    at org.usb4java.LibUsb.<clinit>(LibUsb.java:640)

Answer 1

The description in your exception states

Native library not found in classpath: /org/usb4java/linux-x86/libusb4java.so

What arch is your JVM system?

If your running a x64, the x86 libs won't work and you need to set the native lib to the correct x64 one.

But if you are running an x86 JVM, check, if the file is really there and if it is correct. Maybe something went wrong, when you unpacked it? Or it is in another folder?

Answer 2

Looks like you forgot to add the libusb4java-1.2.0-linux-x86.jar library in your project.