NoClassDefFoundError in Osgi environment

Question

I am working with osgi on apache karaf and I am trying to use kafka and debezium to run into an osgi environment.

kafka and debezium were not osgi ready (karaf will not consider them as bundles), so I did osgified them using eclipse "Plug-in project". The jars that I osgified them are the following : debezium-embedded, debezium-core, kafka connect-api, kafka connect-runtime.

At the begining I get alot of "Class not found exception" when I try to run debezium..

In order to resolve this problem, I changed the manifest of the two bundles. I added an import package to the caller and an export package to the called bundle. Using this I can solve the classNotFound issue.

After solving all the classNotfound issues, I get NoClassDefFoundError

NoClassDefFoundError means that the class loader could not find the .class when it tries to load them ... But I did import all the packages and export them as well.

Any thoughts how to deal with NoClassDefFoundError in an osgi environement

[EDIT Added code]

This is the class Monitor :

public class Monitor {
    private Consumer<SourceRecord> consumer = new Consumer<SourceRecord>() {

        public void accept(SourceRecord t) {
            System.out.println("Change Detected !");
        }

    };

    public void connect() {

        System.out.println("Engine Starting");
        Configuration config = Configuration.create()
                /* begin engine properties */
                .with("connector.class", "io.debezium.connector.mysql.MySqlConnector")
                .with("offset.storage", "org.apache.kafka.connect.storage.FileOffsetBackingStore")
                .with("offset.storage.file.filename", "d:/pathTooffset.dat")
                .with("offset.flush.interval.ms", 60000)
                /* begin connector properties */
                .with("name", "my-sql-connector").with("database.hostname", "localhost").with("database.port", 3306)
                .with("database.user", "root").with("database.password", "apassword").with("server.id", 10692)
                .with("database.server.name", "localhost")
                .with("database.history", "io.debezium.relational.history.FileDatabaseHistory")
                .with("database.history.file.filename", "d:/pathTOdbhistory.dat")
                .build();
        try {
            // Create the engine with this configuration ...
            EmbeddedEngine engine = EmbeddedEngine.create().using(config).notifying(consumer).build();
            Executor executor = Executors.newFixedThreadPool(1);

            executor.execute(() -> {
                engine.run();
            });
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

And my activator :

public class Activator implements BundleActivator {

public void start(BundleContext context) throws Exception {
    Monitor monitor = new Monitor();
    monitor.connect();
}

public void stop(BundleContext context) throws Exception {
}}

The error can happen if you use the wrong classloader. It looks like the exception happens in the class Monitor. Can you post the relevant contents? — Christian Schneider, Apr 20 '17 at 13:39
@ChristianSchneider The code above worked when I run it as a standalone jar , but the errors happens when i try to run it on osgi karaf — larnouch, Apr 20 '17 at 13:44

score 3 · Accepted Answer · edited May 23 '17 at 11:54

3

The problem must be inside EmbeddedEngine. The error could not initialize class means that some static initialization of the class did not work. See this related question noclassdeffounderror-could-not-initialize-class-error.

I propose to run karaf in debug mode and debug through the initialization of this class.

edited May 23 '17 at 11:54

Community

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answered Apr 20 '17 at 14:02

Christian Schneider

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Thanks for the answer , but could you please answer these questions? why the static intialization errors only happened when I run it on karaf and it did not happen when I run it with a java standalone application? Does this mean that debezium is not compatible with osgi environment? – larnouch Apr 20 '17 at 14:38
Yes. I think debezium is currently not compatible to OSGi. I guess they have assumptions about the class loading that do not work in OSGi. I think you should open an issue in their issue tracker about the problem. – Christian Schneider Apr 21 '17 at 08:15
Debezium JARs do not have OSGi manifests since IIRC none of our 3rd party library dependencies have them, either. Feel free to log an issue to add OSGi manifests to the JARs, though you may want to consider contributing the changes via a pull request to speed things up. – Randall Hauch Apr 21 '17 at 14:06

NoClassDefFoundError in Osgi environment

1 Answers1