When and how to map a MBean to a SNMP table?

Generally, every MBean that is not a singleton, should be mapped (or modeled) to (as) a SNMP table. MBeans that contain lists of other MBeans or Java objects should be mapped to several SNMP tables that share a common base index (i.e., the index of the master MBean/table).

The following steps describe how a MBean can be descriptively mapped to a table:

1. First of all, you need a JMXTableSupport instance which is registered with the MBean server:

   final MBeanServerConnection server =
       ManagementFactory.getPlatformMBeanServer();
   
   final MBeanAttributeMOTableSupport tableSupport =
       new MBeanAttributeMOTableSupport(server);
   

2. Next you need to define how the index of the SNMP table is mapped from MBean data or autogenerated. The mapping is done bidirectional by mapping a MBean to a key uniquely identifying the MBean and an Index (OID) uniquely defining the SNMP table row(MOTableRow). The JMXIndexSupport knows about Key and Index and thus provides the mapping. 
   

   tableSupport.add(oidJvmThreadInstanceEntry,
             new MBeanAttributeMOTableInfo(onameJvmThreading,
   
   // The key provider retrieves all available keys (thus all available MBean instances:
             new MBeanInvokationKeyProvider(onameJvmThreading,
                                            new TypedAttribute("AllThreadIds", long.class),
                                            "getThreadInfo", true),
   ...
             new String[] { "ThreadId" },
   
   // The JMX index support maps from rowIdentidier (= Key) to MBean objectname and ...
             new JMXIndexSupport() {
           public ObjectName mapToRowMBean(Object rowIdentifier) {
             return null;
           }
   
   // from rowIdentfier to index OID and ...
           public OID mapToIndex(Object rowIdentifier) {
             Long l = (Long)rowIdentifier;
             return OctetString.fromHexString(Long.toHexString(l)).toSubIndex(true);
           }
   
   // maps native row ID (key used by MBean) or index to rowIdentifier ...
           public Object getRowIdentifier(Object nativeRowId, int nativeIndex) {
             return nativeRowId;
           }
   
   // maps index OID to rowIdentifier (= Key)
           public Object mapToRowIdentifier(OID rowIndex) {
             if (rowIndex == null) {
               return null;
             }
             OctetString os = new OctetString();
             os.fromSubIndex(rowIndex, true);
             String hexString = os.toHexString();
             return Long.parseLong(hexString, 16);
           }
         }));
   
   

3. Next, each column of the SNMP table needs to be mapped to a MBean attribute or action:

   tableSupport.add(oidJvmThreadInstanceEntry,
             new MBeanAttributeMOTableInfo(onameJvmThreading,
             new MBeanInvokationKeyProvider(onameJvmThreading,
                                            new TypedAttribute("AllThreadIds", long.class),
                                            "getThreadInfo", true),
             new TypedAttribute[] {
             new TypedCompositeDataAttribute(new TypedAttribute("threadId", Long.class)),
             new CombinedBitsType(new TypedAttribute[] {
                                  new EnumBitsType("threadState", Thread.State.class, Thread.State.values(), 3),
                                  new BooleanBitsType("inNative", 1),
                                  new BooleanBitsType("suspended", 2)}),
             new TypedCompositeDataAttribute(new TypedAttribute("blockedCount", Long.class)),
             new TypedCompositeDataAttribute(new TypedAttribute("blockedTime", Long.class)),
             new TypedCompositeDataAttribute(new TypedAttribute("waitedCount", Long.class)),
             new TypedCompositeDataAttribute(new TypedAttribute("waitedTime", Long.class)),
             new MBeanProxyType(server, onameJvmThreading, Long.class,
                                "getThreadUserTime",
                                new TypedCompositeDataAttribute(new TypedAttribute("threadId", long.class))) {
               public Object transformFromNative(Object nativeValue, ObjectName objectName) {
                 Long result = (Long) super.transformFromNative(nativeValue, objectName);
                 if ((result == null) || (result < 0)) {
                   return 0L;
                 }
                 return result;
               }
             },
             new TypedCompositeDataAttribute(new TypedAttribute("threadName", String.class)),
             new TypedCompositeDataAttribute(new TypedAttribute("lockOwnerName", String.class)),
             new TypedCompositeDataAttribute(new TypedAttribute("lockOwnerId", Long.class)) {
               public Object transformFromNative(Object nativeValue, ObjectName objectName) {
                 Long result = (Long)super.transformFromNative(nativeValue, objectName);
                 if ((result == null) || (result < 0)) {
                   return "0.0";
                 }
                 OID rowPointer = new OID(JvmManagementMib.oidJvmThreadInstanceEntry);
                 rowPointer.append(JvmManagementMib.colJvmThreadInstId);
                 String index = Long.toHexString(result);
                 OctetString os = OctetString.fromHexString(index);
                 rowPointer.append(os.toSubIndex(true));
                 return rowPointer.toString();
               }
             }},
             new String[] { "ThreadId" },
             new JMXIndexSupport() {
           public ObjectName mapToRowMBean(Object rowIdentifier) {
             return null;
           }
   
           public Object getRowIdentifier(Object nativeRowId, int nativeIndex) {
             return nativeRowId;
           }
   
           public OID mapToIndex(Object rowIdentifier) {
             Long l = (Long)rowIdentifier;
             return OctetString.fromHexString(Long.toHexString(l)).toSubIndex(true);
           }
   
           public Object mapToRowIdentifier(OID rowIndex) {
             if (rowIndex == null) {
               return null;
             }
             OctetString os = new OctetString();
             os.fromSubIndex(rowIndex, true);
             String hexString = os.toHexString();
             return Long.parseLong(hexString, 16);
           }
   }));
   

4. Finally, the table model of the MOTable has been set to the JMXTableModel bound to the table support and table OID created in the previous steps:

   JMXTableModel jvmMemMgrPoolRelEntryModel =
       JMXTableModel.getDefaultInstance(oidJvmMemMgrPoolRelEntry,
                             tableSupport,
                             super.getJvmMemMgrPoolRelEntry().getColumns());
   ((MOTableJMX)super.getJvmMemMgrPoolRelEntry()).
       setModel(jvmMemMgrPoolRelEntryModel);