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How can I imagine polymorphism in JMX?

I have types like this:

public interface Numbering { List<NumberingComponent> getComponents(); } public interface NumberingComponent { Object getValue(); } public interface StringNumberingComponent extends NumberingComponent { String getValue(); } public interface IntegerNumberingComponent extends NumberingComponent { Integer getValue(); }

This is all good and good, unless you try to register an MXBean that uses this type, and you get:

  ... top of exception chain omitted ...
 Caused by: javax.management.openmbean.OpenDataException: Cannot convert type: class com.acme.NumberingComponent
     at com.sun.jmx.mbeanserver.OpenConverter.openDataException (OpenConverter.java:1411)
     at com.sun.jmx.mbeanserver.OpenConverter.toConverter (OpenConverter.java:264)
     at com.sun.jmx.mbeanserver.OpenConverter.makeArrayOrCollectionConverter (OpenConverter.java data15)
     at com.sun.jmx.mbeanserver.OpenConverter.makeParameterizedConverter (OpenConverter.javahaps93)
     at com.sun.jmx.mbeanserver.OpenConverter.makeConverter (OpenConverter.java:296)
     at com.sun.jmx.mbeanserver.OpenConverter.toConverter (OpenConverter.java:262)
     ... 57 more
 Caused by: javax.management.openmbean.OpenDataException: Cannot convert type: interface java.io.Serializable
     at com.sun.jmx.mbeanserver.OpenConverter.openDataException (OpenConverter.java:1411)
     at com.sun.jmx.mbeanserver.OpenConverter.toConverter (OpenConverter.java:264)
     at com.sun.jmx.mbeanserver.OpenConverter.makeCompositeConverter (OpenConverter.java:467)
     at com.sun.jmx.mbeanserver.OpenConverter.makeConverter (OpenConverter.java:293)
     at com.sun.jmx.mbeanserver.OpenConverter.toConverter (OpenConverter.java:262)
     ... 61 more
 Caused by: javax.management.openmbean.OpenDataException: Can't map java.io.Serializable to an open data type
     at com.sun.jmx.mbeanserver.OpenConverter.makeCompositeConverter (OpenConverter.java:454)
     at com.sun.jmx.mbeanserver.OpenConverter.makeConverter (OpenConverter.java:293)
     at com.sun.jmx.mbeanserver.OpenConverter.toConverter (OpenConverter.java:262)
     ... 64 more

Strings and integers are represented in JMX, but Object is not, since at least one getter must be present in the class so that it recognizes it as a useful type. I know that any attempt to add an abstraction layer will not help, because NumberingComponent itself is already such a layer. The original version of the interfaces also had generics, but I removed them to simplify them, and it fails in the same way with or without them.

Is there any other way that I can do by matching this with a composite type? I googled an exception message and didn't get any hits at all. (!!)

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1 answer

You could create the StringNumberingComponent and IntegerNumbering interfaces, also extending the CompositeDataView . Assuming that the MBean MBeanInfo indicates the correct CompositeType for the attribute, MBeanServer will "display" this attribute as an instance of CompositeData that will serialize correctly.

The method that specific implementations need to implement is quite simple, since your CompositeType will have only one field:

 public CompositeData toCompositeData(CompositeType ct)

There is a decent example in JavaDoc .

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