即使我的接口带有默认方法实现，为什么 WELD 仍会抛出 UnsupportedOperationException？

Question

A few days weeks RedHat released JBoss EAP 7.1.0 and so I've started to do some first tests with our application (EAR with Model (JPA), EJB (CDI) and Web). We've used EAP 7.0.7 recently – so the version gap is rather small.

It took only a few seconds to run into the first major problem. WELD now throws an org.jboss.weld.exceptions.UnsupportedOperationException without any additional message whenever we try to call a default implementation provided by an interface. Why are default implementations from interfaces not supported?

NOTE: The interface implements this method... it's not the empty method declaration!

Here is an example for such an interface:

public interface Feature {
    default boolean desiresNewConversation() {
        return false;
    }
}

A simple bean implementing that interface:

@Named
public class MyFeature implements Feature, Serializable {
    public String getName() {
        return "Example";
    }
    // Class does NOT override the default method of the interface.
}

A simple manager class for the UI:

@Named
public class FeatureManager implements Serializable {
    public void start(Feature f) {
        // ...
    }
    public String propagation(Feature f) {
        return f.desiresNewConversation() ? "none" : "join";
    }
}

And the xhtml referencing that method:

<h:form>
    <h:commandButton value="#{myFeature.name}" action="#{featureManager.start(myFeature)}">
        <f:param name="conversationPropagation" value="#{featureManager.propagation(myFeature)}" />
    </h:commandButton>
</h:form>

This throws the following shortened stacktrace:

Caused by: org.jboss.weld.exceptions.UnsupportedOperationException: 
    at org.jboss.weld.bean.proxy.CombinedInterceptorAndDecoratorStackMethodHandler.invoke(CombinedInterceptorAndDecoratorStackMethodHandler.java:49)
    at my.package.MyFeature$Proxy$_$$_WeldSubclass.desiresNewConversation(Unknown Source)
    at my.package.FeatureManager.propagation(FeatureManage.java:67)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at javax.el.ELUtil.invokeMethod(ELUtil.java:311)
    ... 107 more

This is only a simple example. I'm having this effect on many other default methods provided by interfaces. The WeldSubclass won't handle those implementations anymore which made no problem with EAP 7.0.7 and earlier versions.

As soon as I override that method in MyFeature those exceptions are gone.

@Named
public class MyFeature implements Feature {
    public String getName() {
        return "Example";
    }
    @Override
    public boolean desiresNewConversation() {
        return Feature.super.desiresNewConversation();
    }
}

Our application uses several of these default interface implementations and consists of many hundreds of classes implementing those interfaces. Is there any practical way to solve this other then avoiding default interface implementations at all?

PS : Keep in mind that WeldSubclass is a proxy applied by WELD and not my own class. The exception is thrown by the newer WELD implementation of EAP 7.1.0 compared to EAP 7.0.7 where this was legit. And the exception is not even explained with any additional information that might give some reasons for that unexpected change.

Answer 1

So it turns out that I've run into https://issues.jboss.org/browse/WELD-2407 which is solved with WELD v2.4.5.Final – EAP v7.1.0 and v7.1.1 still use WELD v2.4.3 (redhat).

Patching EAP v7.1.1 with WELD v2.4.6.Final solved it. But unfortunately I'll have to wait for an official EAP release.

localhost:JBoss-EAP-7.1 daniel$ bin/jboss-cli.sh 
You are disconnected at the moment. Type 'connect' to connect to the server or 'help' for the list of supported commands.
[disconnected /] connect
[standalone@localhost:9990 /] patch apply /Users/daniel/Downloads/wildfly-11.0.0.Final-weld-2.4.6.Final-patch.zip --override-all
{
    "outcome" : "success",
    "response-headers" : {
        "operation-requires-restart" : true,
        "process-state" : "restart-required"
    }
}
[standalone@localhost:9990 /]