为什么会收到ClassNotFoundException？

Question

Using Ubuntu

Here is my code:

import java.io.*;
import java.net.*;
import se.opendataexchange.ethernetip4j.clx.*;

class PLCServer
{
    public static void main(String argv[]) throws IOException
    {
        // IP address of the ethernet card
        String ENBTIP = "192.168.10.14";
        DataInputStream socketReader = null;
        PrintStream socketWriter = null;
        ControlLogixConnector test = new ControlLogixConnector(ENBTIP,44818);

        // Debugging code
        System.out.println(InetAddress.getByName(ENBTIP).isReachable(10000));
    }
}

Here is how I am compiling:

javac -classpath /home/nick/Java/PLC/ethernetip4j-0.2.jar PLCServer.java which returns no errors

Here is the output:

Exception in thread "main" java.lang.NoClassDefFoundError: se/opendataexchange/ethernetip4j/clx/ControlLogixConnector
    at PLCServer.main(PLCServer.java:13)
Caused by: java.lang.ClassNotFoundException: se.opendataexchange.ethernetip4j.clx.ControlLogixConnector
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    ... 1 more

Am I missing something here?

Answer 1

Make sure you're also specifying the classpath when running your code. If you're still having issues after adding everything you need to the java classpath, check that those missing classes are actually in the jars/locations you are specifying. Also you can enable some debug flags to give more information on class loading, etc.

So for example...

java -classpath /home/nick/Java/PLC/ethernetip4j-0.2.jar:. PLCServer