AtmosphereHandlerService: No AtmosphereHandler found. Make sure you define it inside - Atmosphere/atmosphere Wiki

If you see the following exception when using the @AtmosphereHandlerService exception

[org.atmosphere.cpr.AsynchronousProcessor] No AtmosphereHandler found. 
Make sure you define it inside META-INF/atmosphere.xml 
or annotate using @AtmosphereHandlerService.

Make sure you have added the Annotation Processor to your WEB-INF/lib:

        <dependency>
            <groupId>eu.infomas</groupId>
            <artifactId>annotation-detector</artifactId>
            <version>3.0.1</version>
        </dependency>

If found, the following message will be displayed at deployment time

Atmosphere is using org.atmosphere.cpr.DefaultAnnotationProcessor 
for processing annotations

If you did that and still see the exception, it means the Annotation Processor wasn't been able to find your AtmosphereHandler, try to add the following in your web.xml

        <init-param>
            <param-name>org.atmosphere.cpr.packages</param-name>
            <param-value>packages of your classes</param-value>
        </init-param>