Detailed explanation of the simple RMI framework in the Java class library
Detailed explanation of the simple RMI framework in the Java class library
RMI (remote method call) is a technology that realizes remote object communication in a distributed system.Java provides a convenient RMI framework that allows developers to easily create remote objects and call their methods, as if they are local objects.This article will explain the working principle of the simple RMI framework in the Java class library and provide the corresponding Java code example.
The working principle of the RMI framework mainly involves the following parts:
1. Remote interface: Remote interface is the interface defined between the server and the client. It contains a list of method of remote objects.These methods can be called by the client, just like the method of calling the local object.The remote interface must inherit the java.rmi.remote interface, and each method must throw Java.rmi.RMOTEEEPTION exception.
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface MyRemoteInterface extends Remote {
public String remoteMethod() throws RemoteException;
}
2. Remote object implementation: The remote object is a class that realizes the remote interface.Its method will be called by the client, but the actual execution is performed on the server.The remote object must expand java.rmi.Server.UnicastremoteObject class and implement methods in the remote interface.
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class MyRemoteObject extends UnicastRemoteObject implements MyRemoteInterface {
public MyRemoteObject() throws RemoteException {
super();
}
public String remoteMethod() throws RemoteException {
return "Hello, remote method!";
}
}
3. Server side: The server is responsible for creating a remote object instance and binds it to a specific RMI registry so that the client can be accessed.The RMI registry is a registered center for reference to remote objects.The server must inherit the java.rmi.remote base class, and use the REBIND method of the Java.rmi.naming class in the main method to bind the object to the RMI registry.
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class MyRemoteServer {
public static void main(String[] args) {
try {
// Create a remote object instance
MyRemoteInterface remoteObject = new MyRemoteObject();
// Create the RMI registry and bind objects
Registry registry = LocateRegistry.createRegistry(1099);
Naming.rebind("rmi://localhost/MyRemoteObject", remoteObject);
System.out.println("Server started.");
} catch (Exception e) {
e.printStackTrace();
}
}
}
4. Client: The client obtains the reference to the remote object by searching the RMI registry, and then the method of calling the remote object can be used to call the remote object.The client uses the Java.rmi.naming class lookup method to find object reference from the RMI registry.
import java.rmi.Naming;
public class MyRemoteClient {
public static void main(String[] args) {
try {
// Find remote object reference from the RMI registry
MyRemoteInterface remoteObject = (MyRemoteInterface) Naming.lookup("rmi://localhost/MyRemoteObject");
// The method of calling the remote object
String result = remoteObject.remoteMethod();
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Through the above steps, we can implement remote methods between the server and the client.The RMI framework allows developers to easily share objects in a distributed system and call remote objects.This provides the foundation for building a powerful and flexible distributed application.
I hope that the Java code example and working principle provided in this article will help you understand the operation of the simple RMI framework in the Java class library.
