WebSocket Endpoint OSGi @Component with Multivalued property fails with java.lang.ClassCastException

• Type: Bug
• Status: Closed
• Resolution: Duplicate
• Affects Version/s: 7.0.X, 7.1.X, Master
• Fix Version/s: Master
• Component/s: Core Infrastructure
• Labels:
  • 7.1-won't
  • ee-ts
• Fix Priority: 3
• Git Pull Request: https://github.com/lipusz/liferay-portal/pull/213
• Bug Type: Default
• What problem did the customer find?: Multivalued OSGi @Component property item fails to get interpreted as java.util.List
• What do you think is the root cause? (if known): Portal code in com.liferay.websocket.whiteboard.internal.WebSocketEndpointTracker#addingService(..) fails to convert multivalued property item into a String array, and then to a list (array interpretation is missing, conversion is faulty in operation).
• Proposed solution (if any):
  Hide

  Implement the proper conversion routine for multivalued OSGi @Component property items: ; - from String to String array (even if it is a single item) ; - from String array to List<Class<?>> ; -- using Class.forName(..) to interpret array items

  Show

  Implement the proper conversion routine for multivalued OSGi @Component property items: - from String to String array (even if it is a single item) - from String array to List<Class<?>> -- using Class.forName(..) to interpret array items

USE CASE
We want to configure "org.osgi.http.websocket.endpoint.encoders" to be able to serialize objects to JSON and send them. The problem is that the method providing the value via @Component property does not work because Encoders has to be a list.

ISSUE:
OSGi @Component property item fails to get interpreted as java.util.List.

REPRODUCTION STEPS:
1. use official resources:
https://dev.liferay.com/de/develop/tutorials/-/knowledge_base/7-0/liferay-websocket-whiteboard
2. update the code to provide multi valued property items
e.g.

@Component(
    immediate = true,
    property = {
		"org.osgi.http.websocket.endpoint.path=/o/echo",
		"org.osgi.http.websocket.endpoint.encoders=com.liferay.websocket.example.json.JsonEncoder",
		"org.osgi.http.websocket.endpoint.encoders=com.liferay.websocket.example.json.AnotherEncoder",
		"org.osgi.http.websocket.endpoint.decoders=com.liferay.websocket.example.json.ADecoder"
	},
    service = Endpoint.class
)
public class EchoWebSocketEndpoint extends Endpoint {

    @Override
    public void onOpen(final Session session, EndpointConfig endpointConfig) {
        session.addMessageHandler(
            new MessageHandler.Whole<String>() {
            @Override
            public void onMessage(String text) {
                try {
                    RemoteEndpoint.Basic remoteEndpoint =
                        session.getBasicRemote();
                    remoteEndpoint.sendText(text);
                }
                catch (IOException ioe) {
                    throw new RuntimeException(ioe);
                }
            }
        });
    }
}

(Note: the encoder class names are just for demonstrating the bug, do not refer to actual classes)
3. build the bundle
4. Start the portal.
5. Deploy the bundle
6 see the error message:

15:57:17,317 ERROR [Framework Event Dispatcher: Equinox Container: 50ad1c64-2e1e-0018-1ca5-ebd598ec68b2][com_liferay_websocket_whiteboard:97] FrameworkEvent ERROR 
java.lang.ClassCastException: java.lang.String cannot be cast to java.util.List
	at com.liferay.websocket.whiteboard.internal.WebSocketEndpointTracker.addingService(WebSocketEndpointTracker.java:66)
	at com.liferay.websocket.whiteboard.internal.WebSocketEndpointTracker.addingService(WebSocketEndpointTracker.java:47)
	at org.osgi.util.tracker.ServiceTracker$Tracked.customizerAdding(ServiceTracker.java:941)

HYPOTHESIS:
Portal code in com.liferay.websocket.whiteboard.internal.WebSocketEndpointTracker#addingService(..) fails to convert multi valued property item into a String[] array, and then to a List<Class>

• array interpretation is missing
• conversion is faulty in operation

PROPOSED SOLUTION:
Implement the proper conversion routine for multi valued OSGi @Component property items:

• from String to String[] array (even if it is a single item)
• from String[] array to List<Class>
  • using Class.forName(..) to interpret String[] array items