Proposed brooklyn Java code to poll an underlying resource, to update attributes (aka sensors) - v2

gistfile1.java

// See v1 proposal at https://gist.github.com/3122130
//
// This example shows use of a builder pattern to construct an immmutable JmxSensorAdapter 
// before passing it to register(...).
//
// Most contentious issues:
//  1. immutability of JmxSensorAdapter
//  2. explicitly passing in entity(...) so can infer the jmx url from its attributes
//  3. use of withObjectName(...) to create a kind of sub-context so subsequent calls to pollAttribute 
//     don't need to keep repeating the object name
//  4. building the JmxSensorAdapter doesn't cause it to start polling; instead need to call 
//     register. Alternatives include:
//    a. get rid of the call to register, and instead pass the registry to the builder
//    b. pass the builder to register


    JmxSensorAdapter.Bulder jmxBuilder = JmxSensorAdapter.builder()
            .entity(this)
            .period(500, TimeUnit.MILLISECONDS);

    jmxBuilder.withObjectName("jboss.web:type=GlobalRequestProcessor,name=http-*")
            .pollAttribute(new JmxAttributePollConfig<Integer>(ERROR_COUNT)
                    .attributeName("errorCount"))
            .pollAttribute(new JmxAttributePollConfig<Integer>(REQUEST_COUNT)
                    .attributeName("requestCount"));

    jmxBuilder.pollAttribute(new JmxAttributePollConfig<Integer>(SERVICE_UP)
            .objectName("jboss.system:type=Server")
            .attributeName("Started")
            .period(1, TimeUnit.SECONDS)
            .onError(Functions.constant(false));

    registry.register(jmxBuilder.build());