The implementation principle of simple RMI framework in the Java library
The implementation principle of simple RMI framework in the Java library
RMI (Remote Method Involution) is a remote call method provided by Java.It allows the calling method and parameter transfer between different Java virtual machines in distributed systems, making it simply calls the method of remote objects located on different JVM as local methods.
The implementation principle of the simple RMI framework can be explained through the following steps:
1. Interface definition: First of all, we need to define an interface, which will define the method of remote objects that can be called.Here we start with a simple example. Suppose we have a calculator interface Calulator, which contains two methods: ADD and Subtract.
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface Calculator extends Remote {
int add(int a, int b) throws RemoteException;
int subtract(int a, int b) throws RemoteException;
}
2. Server implementation: Next, we need to achieve a specific implementation class of this interface.This implementation class will provide specific implementation of the method, and needs to inherit the `java.rmi.server.unicastremoteObject`.
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class CalculatorImpl extends UnicastRemoteObject implements Calculator {
public CalculatorImpl() throws RemoteException {
super();
}
public int add(int a, int b) throws RemoteException {
return a + b;
}
public int subtract(int a, int b) throws RemoteException {
return a - b;
}
}
3. Server registration: On the server, we need to bind the implementation class to a specific name so that the client can find it.This can be achieved by using the `java.rmi.naming` class.
import java.rmi.Naming;
import java.rmi.registry.LocateRegistry;
public class CalculatorServer {
public static void main(String[] args) {
try {
// Create a remote object
Calculator calculator = new CalculatorImpl();
// Create a registry
LocateRegistry.createRegistry(1099);
// Binded remote objects to specific names
Naming.rebind("Calculator", calculator);
System.out.println("Calculator server is ready.");
} catch (Exception e) {
System.out.println("Calculator server failed: " + e);
}
}
}
4. Client call: On the client, we need to use a registry to find the remote object and use it to call the interface method.
import java.rmi.Naming;
public class CalculatorClient {
public static void main(String[] args) {
try {
// Find the remote object
Calculator calculator = (Calculator) Naming.lookup("rmi://localhost/Calculator");
// Call method
int sum = calculator.add(10, 5);
int difference = calculator.subtract(10, 5);
System.out.println("Sum: " + sum);
System.out.println("Difference: " + difference);
} catch (Exception e) {
System.out.println("Calculator client exception: " + e);
}
}
}
5. Execution program: In order to run this simple RMI example, we need to start the server and client in the command line.
Start the server:
java CalculatorServer
Start the client:
java CalculatorClient
The above is the implementation principle of the simple RMI framework in the Java library.By defining interfaces, implementation interfaces, registered remote objects, and clients to call remote methods, we can implement remote calls of the Java method in the distributed system.
