2.3.3 Protocol Adaptors

Protocol adaptors have only a server component and provide a view of an agent and its MBeans through a different protocol. Protocol adaptors can also translate requests that are formulated in this protocol into management requests on the JMX agent. The view of the agent and the range of possible requests depends upon the given protocol.

For example, Java DMK provides an HTML adaptor that presents the agent and its MBeans as HTML pages that are viewable in any web browser. Because the HTML protocol is text based, only data types that have a string representation can be viewed through the HTML adaptor. However, this is sufficient to access most MBeans, view their attributes, and invoke their operations.

Due to limitations of the chosen protocol, adaptors have the following limitations.

• Not all data types are necessarily supported

• Not all management requests are necessarily supported, because some requests might rely on unsupported data types

• Notifications from a broadcaster MBean might not be supported

• A given protocol adaptor might require private data structures or helper MBeans for responding to requests

The SNMP adaptor provided in the Java DMK is limited by the constraints of SNMP. The richness of the JMX architecture cannot be translated into SNMP, but all the operations of SNMP can be imitated by methods of the MBean server. This translation requires a structure of MBeans that imitates the MIB. While an SNMP manager cannot access the full potential of the JMX agent, the MBeans representing the MIB are available for other managers to access and incorporate into their management systems.

In general, a protocol adaptor tries to map the elements of the JMX architecture into the structures provided by the given protocol. However, the completeness or accuracy of this mapping is not guaranteed.