Java Management Extension (JMX) provides a powerful mechanism to monitor and manage Java applications. It can be enabled in Tomcat to monitor threads, CPU usage, and heap memory, and to configure MBeans. Spring provides JMX support out of the box, and we can use it to easily integrate our Spring application into JMX architecture.

JMX support provides the following core features:

• Easy and flexible support for controlling the management interface of beans
• Declarative support for exposing MBeans over remote connectors
• Automatic registration of Spring beans as JMX MBean
• Simplified support to proxy both local and remote MBean resources

JMX functionality has three levels:

• Instrumentation level: This level contains the components and resources that are represented by one or more Java beans, which are known as managed beans, or MBean.
• Agent level: This is known as an intermediate agent, called the MBean server. It gets the request from the remote management level and passes it to the appropriate MBean. It can also receive notifications related to state changes from MBeans and forward them back to the remote management level.
• Remote management level: This layer is made of connectors, adapters, or client programs. It sends requests to the agent level and receives the responses to the requests. Users can connect to the MBean server using either a connector or a client program, such as JConsole, with a protocol such as Remote Method Invocation (RMI) or Internet Inter-ORB Protocol (IIOP), and use an adapter.

In short, a user at the remote management level sends a request to the agent level, which finds the appropriate MBean at the instrumentation level, and sends the response back to the user.