Local and Remote Proxies

Proxies may also be bound to objects called handlers which necessarily implement the ProxyHandler interface. The methods of this interface are a subset of MBean server methods, as listed in Table 8-1 (see "The RemoteMBeanServer Interface"). These are the only methods that a proxy needs to in order to access its corresponding MBean and fulfill all management requests.

In the Java Dynamic Management Kit, the RemoteMBeanServer interface extends the ProxyHandler interface, meaning that proxy objects may be bound to any of the connector clients. These are called remote proxies, because they are instantiated in an application which is distant from the agent and its MBean instances.

As a new feature in version 4.2 of the product, the implementation of the MBeanServer interface also implements the ProxyHandler interface, so that proxy objects may be bound to the MBean server itself. These are called local proxies because they are located in the same application as their corresponding MBeans. Local proxies help preserve the management architecture by providing the simplicity of performing direct method calls on MBeans, while still routing all operations through the MBean server.

The symmetry of remote and local proxies complements the symmetry that allows management components to execute either in an agent or in a management application. Provided that all proxy classes are available, management components which use MBean proxies may be instantiated in an agent and rely on the MBean server or may be instantiated in a remote manager where they interact with a connector client. Except for communication delays, the results of all operations will be identical, and the same notifications will be received, whether obtained through a local proxy or a remote proxy (see "Adding a Listener Through the Connector").

The following diagram shows local proxies which are instantiated in an agent and bound to the MBean server, and the same classes instantiated as remote proxies in a management application and bound to the connector client. Management components located in either the agent or management application can interact with the local or remote proxies, respectively. Management components may also access the MBean server or the connector client directly, regardless of whether proxies are being used.

Figure 9-1 Interacting with Local and Remote Proxies

This diagram shows all possible relations between management components, proxies and their MBeans. Standard proxies can only represent a specific standard MBean, and generic proxies may represent any standard or dynamic MBean. In a typical management scenario, the management components will be located in only one application, and for simplicity, they will rarely instantiate more than one type of proxy.

Throughout the rest of this topic, we do not distinguish between local and remote proxies. A proxy object, either standard or generic, is used in exactly the same way regardless of whether it is instantiated locally or remotely.