2.3.1.4 Generating Proxies

Java DMK supports the notion of proxies. Proxies simplify the interactions between an application and the MBeans the application wants to manage. The purpose of a proxy is to invoke the methods that access the attributes and operations of an MBean, through its MBean server. The proxy performs the task of constructing the method calls at every invocation, on behalf of the caller:

• Getting or setting attributes

• Invoking operations

• Registering or unregistering for notifications

Conceptually, a proxy instance makes the MBean server and, optionally, a protocol connector completely transparent. With the exception of MBean registration and connector connection phases, all management requests on MBeans can be fully served through proxies, with identical results, apart from some details concerning exceptions. However, all functionality of the Java DMK is available without using proxies, so their use is never mandatory.

Figure 2–1 shows management components interacting with an MBean through a proxy.

Figure 2–1 Binding Proxy MBeans to Local and Remote Servers

Figure 2–1 also shows that proxies can be instantiated either locally in the agent or remotely in the manager. Since the MBean server and the connector client have the same API, management requests to either of them are identical. This creates a symmetry so that the same management components can be instantiated either in the agent or in the manager application. This feature contributes to the scalability of Java dynamic management applications.

In Java DMK 5.0, proxies were generated using the proxygen tool, supplied with Java DMK 5.1 but now deprecated. This tool is still needed if proxies are required for legacy connectors. However, Java DMK 5.1 provides a useful enchancement for generating proxies. Because Java DMK 5.1 is an implementation of JMX 1.2, you can generate a proxy object at runtime given just its Java interface, using the dynamic proxies provided with the J2SE platform (java.lang.reflect.Proxy). These proxies cannot be used with the legacy connectors.