Using CDI/injection in Tomcat Websocket / Serverendpoint

Question

i am using tomcat 9.0.4 and Java 1.8. In the same project, jersey is providing an webservice. I can use @Inject from the webservice classes without any problem. I am trying to get injection working from my websocket endpoint display below.

@ApplicationScoped
@ServerEndpoint("/endpoint")
public class ArchApi {

  @Inject RepClass injectedClass;

  @OnMessage()
  public String onMessage(byte[] data) {
       injectedClass.doThings("test");
  }

}

This is my CDI implementation:

    <dependency>
        <groupId>org.glassfish.jersey.inject</groupId>
        <artifactId>jersey-hk2</artifactId>
        <version>2.27</version>
    </dependency>

All i get is a java.lang.NullPointerException.

I found this feature request. So i think Injection is still not implemented in tomcat.

My questions:

• How do i proper write my incomming data to my repository?
• Is there another way to get Injection working?

At the moment i am thinking about a migration to glassfish, which should support injection from a Serverendpoint

Answer 1

You could use the following configurator to make CDI manage the endpoint classes:

public class CdiAwareConfigurator extends ServerEndpointConfig.Configurator {

    public <T> T getEndpointInstance(Class<T> endpointClass) throws InstantiationException {
        return CDI.current().select(endpointClass).get();
    }
}

Then annotate your endpoint classes as following:

@ServerEndpoint(value = "/chat", configurator = CdiAwareConfigurator.class)
public class ChatEndpoint {
    ...
}

Depending on your CDI configuration, you may need to annotate the endpoint classes with @Dependent.

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Alternatively you could programmatically look up for a bean instance using:

SomeSortOfBean bean = CDI.current().select(SomeSortOfBean.class).get();