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The result of the method invocation such as a return value is transported back across the network to be delivered to the client by RMI. Think of a television as the remote object to be called.
The remote control for our television is the remote interface. The infrared protocol sent by the remote control and picked up by the television is like the RMI protocol. Figure A. Like the EJB object discussed in chapter 5 , RMI works through proxies on both the client and remote object endpoints to transparently provide distributed computing as a service. RemoteException in their throws clause. When you annotate a session bean business interface using the Remote annotation as we did in chapters 2 and 3 , the container automatically makes the bean callable via RMI as a remote object.
Similarly, when you inject a remote bean using the EJB annotation, the container talks to the bean through RMI under the hood. The greatest benefit for RMI is that it provides location transparency. The client invokes methods on a remote object as if the object were located in the same virtual machine, without having to worry about the underlying plumbing.
As compelling as RMI might seem from our very high-level discussion, like all technologies it has its own set of problems. Remote object invocation uses pass-by-value semantics. When the client passes a parameter to the remote method, RMI sends the data held by the object across the network as a byte stream. The byte stream is received by RMI on the other end of the communication tunnel, copied into an object of the same type as passed in by the client, and weaved in as a parameter to the remote object.
Objects returned by the remote method go through the same translation-transport-translation steps. The process of turning an object into a byte stream is called marshaling , and the process of turning a byte stream into an object is called unmarshaling. This is exactly why all objects transported across the network by RMI must implement the java.
Serializable interface. For large objects, the cost of marshaling and unmarshaling can be pretty high, making RMI a performance bottleneck compared to local invocation. This is why you want to make sure that objects passed over RMI are not large, because they can slow down your application.
This property specifies the location of the registry when the registry is being used as the initial context. The default value of this property is "rmi:", signifying a registry running on port of the local host. A colon-separated list of the fully qualified class names of state factory classes used to get an object's state for storing given the object itself.
You can use this mechanism to transform an object into forms that can be stored into the registry. The RMI registry service provider supports storing java. Remote , javax. Reference , and javax. Referenceable objects. See javax. A colon-separated list of the fully qualified class names of object factory classes for transforming objects read from the registry.
You can use this mechanism to transform an object into forms expected by the application. This property specifies the socket factory for use by the RMI runtime in order to obtain the client sockets to make RMI calls. The value specified for the socket factory must be of the type java. If this property is not set, the default socket factory is used by the registry.
This property, when set to any value, indicates that the provider should attempt to install the RMISecurityManager. See the Security Considerations section below. The RMI registry supports a flat namespace. Since there is no hierarchy, every name is atomic.
Each name may be composed of any characters, and case is significant. Names are passed as arguments to the methods of a registry context, and are returned as the results of those methods, either as Name objects or as strings. When a Name object is used, it should have a single component whose value is the atomic name that will be passed on to the registry. When a string is used as a name, it is interpreted as the string representation of a composite name.
So if ctx is a registry context, for example, then the following two unbind operations are equivalent:. These characters must be properly escaped or quoted. Register or Login. Welcome back! Reset Your Password We'll send an email with a link to reset your password.
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