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This is the follow up to https://dev.clojure.org/jira/browse/JMX-16.
For the attribute to be writable via JMX it has to be set as writable - see (link: https://github.com/clojure/java.jmx/blob/master/src/main/clojure/clojure/java/jmx.clj#L171 text: build-attribute-info).
That is, Bean deftype implements setAttribute, but implementation of getMBeanInfo calls 2-arity version of map->attribute-infos without an option to set an attribute as writable.