public class MXBeanStatisticsMetadata
extends BasicStatisticsMetadata

MXBeanStatisticsMetadata extends BasicStatisticsMetadata to provide the JMX-specific properties objectName and attributeName. The objectName is the path of the MBean or MXBean inside of the MBean server and the attributeName is the name of the attribute within that MBean or MXBean that represents the desired statistic value. However since an attribute maybe one of the complex types: CompositeData, TabularData, or array of it,
the xpath property is used to specify an accessor to a node within the complex type that is Numeric in nature.
In general, end user can use tools like JConsole, VisualVM, MC4J to explore the object hierarchy of an attribute of a registered MBean or MXBean in order to deduce what the xpath value should be for a given attribute value.
If the attribute is a Numeric primitive, then xpath string is simply "/<attributeName>" because that also happens to be the Numeric node.
If an attribute value is a CompositeData or TabularData with a Numeric field of interest embedded somewhere inside the complex type, then the xpath accessor string gets more interesting. See examples below.
As a rule of thumb, an attribute that is a CompositeData value is mapped to a java.util.Map with keys being the fields inside it.
A TabularData attribute value is also mapped to a java.util.Map with each value in the Map being CompositeData. The key of this Map is a String representation of the set of indexes used to access the TabularData. See Example 4 below.

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Note: Statistics defined using MXBeanStatisticsMetadata must be used in conjunction with an MXBeanStatisticsProvider to achieve automatic lookup of MBean attributes.
Also, the SilverFabric broker do not make use in its classpath any interfaces nor classes from a remote application whose statistics is being collected. This avoids any potential classpath and classloading issues associated with creating a proxy for the MBean or MXBean.

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Here is an example of a Tomcat-specific property:

Statistic Name	JMX ObjectName	Attribute Name	XPath to Numeric node
Tomcat JVM Heap Memory Usage Comitted	java.lang:type=Memory	HeapMemoryUsage	/HeapMemoryUsage/comitted

The above MXBean attribute is defined as an MXBeanStatisticsMetadata in XML as shown below:

 <statisticsProvider class="com.datasynapse.fabric.stats.provider.MXBeanStatisticsProvider">
    <mBeanServerRef class="TomcatMBeanServerRef"/>
    <supportedStatistic class="com.datasynapse.fabric.stats.MXBeanStatisticsMetadata"> 
       <property name="name" value="Tomcat JVM Heap Memory Usage Committed"/>
       <property name="description" value="JVM Heap Memory Usage that is comitted"/>
       <property name="objectName" value="java.lang:type=Memory"/>
       <property name="attributeName" value="HeapMemoryUsage"/>
       <property name="xpath" value="/HeapMemoryUsage/comitted"/> 
       <property name="default" value="true"/> 
       <property name="units" value="MB"/>
       <aggregator class="SourceAveragedAggregator"/>
    </supportedStatistic>
    ...
 </statisticsProvider>
 

Some more examples of usage and format of the xpath property to retrieve value of interest:

 Example 1: Get the "bytesReceived" attribute for a MBean with registered
            ObjectName "Catalina:type=GlobalRequestProcessor,name=\"http-apr-9090\"".
            where the attribute is a Long.
            
            <property name="objectName" value="Catalina:type=GlobalRequestProcessor,name=\"http-apr-9090\""/>
            <property name="attributeName" value="bytesReceived"/>
            <property name="xpath" value="/bytesReceived"/>
            
            
 Example 2: Get the "max" memory value from the "HeapMemoryUsage" attribute for a MXBean with registered
            ObjectName "java.lang:type=Memory".
            where the attribute is a CompositeData object.
            
            
            <property name="objectName" value="java.lang:type=Memory"/>
            <property name="attributeName" value="HeapMemoryUsage"/>
            <property name="xpath" value="/HeapMemoryUsage[@name='max']"/>
            
           

 Example 3: Get the "used" memory value from the attribute LastGcInfo, with a TabularData value "memoryUsageBeforeGc",
            and accessible with TabularData key "[Perm Gen [shared-rw]]"
            for the MXBean registered as "java.lang:type=GarbageCollector,name=Copy".
            
            
            <property name="objectName" value="java.lang:type=GarbageCollector,name=Copy"/>
            <property name="attributeName" value="LastGcInfo"/>
            <property name="xpath" value="/LastGcInfo/memoryUsageBeforeGc[@name='[Perm Gen [shared-rw]]']/value[@name='used']"/>
            
            
 Example 4: Aggregate all  active sessions from the attribute "activeSessions" related to all MBeans
            registered like "Catalina:type=Manager,*" .
            
            <property name="objectName" value="Catalina:type=Manager,*"/>
            <property name="attributeName" value="activeSessions"/>
            <property name="xpath" value="/activeSessions"/>