The technical foundation of the simple RMI framework in the Java class library
The technical foundation of the simple RMI framework in the Java class library
Overview
Remote METHOD Invocation (RMI) is a technology for achieving communication between remote objects in Java applications.The Java class library provides a simple RMI framework that allows developers to easily implement remote methods in a distributed system.
The technical foundation of the RMI framework
The Java RMI framework is based on the following important technical foundations:
1. Java remote interface (Remote Interface): Remote interface is an interface that contains interaction between the client and the server.It defines the remote method that the client can call and specifies the logic that the server needs to implement.The remote interface is the core component of the RMI framework.
The following is a simple regular interface example code:
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface GreetingService extends Remote {
String sayHello(String name) throws RemoteException;
}
2. RMI Server (RMI Server): The RMI server is a server that provides remote object instances and waiting for client requests.The server needs to implement remote interfaces and register it into the RMI registry.The RMI server uses the RMI registry to bind the reference to the remote object so that the client can locate and call the remote method.
The following is an example code for a simple RMI server:
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class GreetingServiceImpl extends UnicastRemoteObject implements GreetingService {
protected GreetingServiceImpl() throws RemoteException {
super();
}
public String sayHello(String name) throws RemoteException {
return "Hello, " + name + "!";
}
public static void main(String[] args) {
try {
GreetingService greetingService = new GreetingServiceImpl();
Registry registry = LocateRegistry.createRegistry(1099);
registry.rebind("GreetingService", greetingService);
System.out.println("RMI Server started.");
} catch (Exception e) {
e.printStackTrace();
}
}
}
3. RMI client (RMI Client): The RMI client is an application that calls the remote method through remote interface.The client uses the RMI registry to find and obtain the reference to the remote object, and then use this reference to call the remote method.
The following is an example code for a simple RMI client:
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class GreetingServiceClient {
public static void main(String[] args) {
try {
Registry registry = LocateRegistry.getRegistry("localhost", 1099);
GreetingService greetingService = (GreetingService) registry.lookup("GreetingService");
String result = greetingService.sayHello("Alice");
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Summarize
The simple RMI framework in the Java class library provides the implementation mechanism of remote method calls to achieve communication between remote objects in distributed systems.It is based on the technical foundation of Java remote interface, RMI server and RMI client, so that developers can easily realize the function of remote method calling.By understanding and familiar with these technical foundations, we can better use the simple RMI framework in the Java class library to develop a distributed system.
