How to fix "java.lang.NoClassDefFoundError: com/microsoft/azure/eventhubs/EventHubClient$" error in Java - azure-eventhub

Question

Java Version: 1.8
Azure EventHubs Version: 3.0.1
I'm trying to connect to my EventHubClient by calling:
EventHubClient.createFromConnectionStringSync(connStr.toString(), executorService)
However, this call is throwing a NoClassDefFoundError of the following:
java.lang.NoClassDefFoundError: com/microsoft/azure/eventhubs/EventHubClient$
Usually when I run into a NoClassDefFoundError, it is because I didn't import the corresponding package. However, in this case, I have the Azure EventHub package imported. The thing that is confusing me the most is the '$' at the end of EventHubClient.
Has anyone ran into this issue before and know what may be causing it?

Answer 1

Firstly, i suppose that the official code is totally right and nothing wrong with your jdk version and event hub package version because i tested the sample code with your environment and it works for me.
dependencies:
Sample code:
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.microsoft.azure.eventhubs.ConnectionStringBuilder;
import com.microsoft.azure.eventhubs.EventData;
import com.microsoft.azure.eventhubs.EventHubClient;
import com.microsoft.azure.eventhubs.EventHubException;
import java.io.IOException;
import java.nio.charset.Charset;
import java.time.Instant;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
public class SimpleSend {
public static void main(String[] args)
throws EventHubException, ExecutionException, InterruptedException, IOException {
final ConnectionStringBuilder connStr = new ConnectionStringBuilder()
.setNamespaceName("jaygongeventhub")
.setEventHubName("jaygong")
.setSasKeyName("RootManageSharedAccessKey")
.setSasKey("4RXaJ2NPwz635HYlOpKGMCh89N/9i1kz3PSAC9WeYq0=");
final Gson gson = new GsonBuilder().create();
final ScheduledExecutorService executorService = Executors.newScheduledThreadPool(4);
final EventHubClient ehClient = EventHubClient.createFromConnectionStringSync(connStr.toString(), executorService);
try {
for (int i = 0; i < 10; i++) {
String payload = "Message " + Integer.toString(i);
byte[] payloadBytes = gson.toJson(payload).getBytes(Charset.defaultCharset());
EventData sendEvent = EventData.create(payloadBytes);
ehClient.sendSync(sendEvent);
}
System.out.println(Instant.now() + ": Send Complete...");
System.out.println("Press Enter to stop.");
System.in.read();
} finally {
ehClient.closeSync();
executorService.shutdown();
}
}
}
Output:
Secondly, based on your error detail: NoClassDefFoundError,which is different with ClassNotFoundException. ClassNotFoundException comes when JVM tries to the load a class at runtime dynamically means you give the name of the class at runtime and then JVM tries to load it and if that class is not found in the classpath it throws java.lang.ClassNotFoundException. While in the case of NoClassDefFoundError the problematic class was present during Compile time and that's why the program successfully compiled but not available during runtime for any reason.
I suggest you checking below solutions or points to try to solving the issue:
1) The class is not available in Java Classpath.
2) You might be running your program using jar command and class was not defined in manifest file's ClassPath attribute.
3) Any start-up script is overriding Classpath environment variable.
4) Because NoClassDefFoundError is a subclass of java.lang.LinkageError it can also come if one of it dependency like native library may not available.
4) Check for java.lang.ExceptionInInitializerError in your log file. NoClassDefFoundError due to the failure of static initialization is quite common.
5) If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause java.lang.NoClassDefFoundError, see examples and scenario section for detailed discussion.
Read more: https://javarevisited.blogspot.com/2011/06/noclassdeffounderror-exception-in.html#ixzz62y4liZ3G
Read more: https://javarevisited.blogspot.com/2011/06/noclassdeffounderror-exception-in.html#ixzz62y4NPiEB