Not easy to customize DefaultWebSocketProcessor

[flowersinthesand]

First it may be a uncommon case to customize WebSocketProcessor but anyway I found these problems in doing that.

1. WebSocketProcessorFactory swallows java.lang.InstantiationException

I couldn't know why my customized WebSocketProcessor extending DefaultWebSocketProcessor doesn't work. After the debugging, I found that WebSocketProcessorFactory swallows java.lang.InstantiationException occurred due to constructor arguments mismatch and provides an instance of the default one instead without any log.

atmosphere/modules/cpr/src/main/java/org/atmosphere/cpr/WebSocketProcessorFactory.java

Lines 80 to 82 in 8e5b249

	} catch (Exception ex) {
	processor = new DefaultWebSocketProcessor(framework);
	}

1. DefaultWebSocketProcessor doesn't have empty constructor.

If a given class is not the default one, WebSocketProcessorFactory creates a customized processor using ObjectFactory from AtmosphereFramework. But it can't handle constructor args so it's not possible to extend DefaultWebSocketProcessor directly and use it. In other words, ObjectFactory requires empty constructor but DefaultWebSocketProcessor doesn't provide it so its sub class can't have it.

atmosphere/modules/cpr/src/main/java/org/atmosphere/cpr/WebSocketProcessorFactory.java

Lines 78 to 79 in 8e5b249

	processor = framework.newClassInstance(WebSocketProcessor.class,
	(Class<WebSocketProcessor>) IOUtils.loadClass(getClass(), webSocketProcessorName));

1. A customized WebSocketProcessor can't access to AtmosphereFramework

For the above reason, a customized WebSocketProcessor must have empty constructor and not extend DefaultWebSocketProcessor (and can create DefaultWebSocketProcessor internally to delegate methods calls) but in this case it can't get the corresponding AtmosphereFramework unless it uses a special object factory or something other way allowing injecting AtmosphereFramework.

Finally I solved it by creating my own object factory to intercept a method call to provide my customized processor when it's required.
https://github.com/vibe-project/vibe-java-platform/blob/9b8fc1bb6ddb276135422d5fb77a0ca7f9f8582f/atmosphere2/src/main/java/org/atmosphere/vibe/platform/server/atmosphere2/AtmosphereBridge.java#L76-L78