WebLogic JMX

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WebLogic JMX

• Weblogic implements SUN JMX1.0 (Java Management Extensions)
All WebLogic Server resources are managed through these JMX-based services.For easy understanding, consider the following : JDBC connection Pool (snippet from config.xml)

<JDBCConnectionPool DriverName=”oracle.jdbc.xa.client.OracleXADataSource” Name=“Pool” PasswordEncrypted=”{3DES}DpbT3SFF8mI=”InitialCapacity=”5″ MaxCapacity=”35″URL=”jdbc:oracle:thin:@localhost:1521:Mysql”/>

The JDBC connection pool resource is exposed as Mbean called “JDBCConnectionPoolMBean”
•For JDBCConnectionPoolMBean, there are lot of other attributes with default values. The values that we add through console override the default values.(like MinCapacity,MaxCapacity etc).An Mbean is just a concrete java class that is coded as per JMX specification and it provides a set of setters and
getters of the attributes.
In our example, we can invoke JDBCConnectionPoolMBean and then change the attribute like initial capacity via JMX
program.

•There are another set of Mbeans called runtime Mbeans.
As the name implies, this is read only and used to monitor/get the runtime values.
Extending our same JDBC pool example, the related runtime Mbean is :
JDBCConnectionPoolRuntimeMBean.
If we see the API, we can see methods like:
getActiveConnectionsCurrentCount()
These are runtime values at the particular instant.
General rule of thumb is, Mbeans for which the change involves persisting data to config.xml are termed as
configuration Mbeans.
(JDBC pool capacity, driver name, timeout value etc).
Mbeans that involve read-only data is termed a runtime Mbean.
The API documentation will give a better picture of all the methods. As shown in the example, we have configMbeans as well as RuntimeMbeans for all weblogic resources(JDBC,JMS,EJB etc).This provides an easy way for other vendors like vignette to monitor and administer weblogic resources.

When are these configMbeans created?
yes, at startup, Admin Server creates these Mbeans (for each resource) from config.xml and managed servers when they startup, connect to admin server and get a copy of these Mbeans into their local memory. RuntimeMbeans are created at rutime and they reflect the in instantaneous values.