Introduction and use of the "Simple RMI" framework in the Java class library
Simple RMI is a remote method call in the Java library (RMI) framework (RMI), which provides a convenient way to realize the method call in distributed systems.RMI is a mechanism that allows communication between the Java virtual machine (JVM) and enables the object in one JVM to call the method in another JVM, just like calling the local method.
Simple RMI solves many common problems required when constructing a distributed system, such as network communication, serialization and remote objects of life cycle management.Using Simple RMI, we can publish a Java object as remote object (Remote Object). Other JVMs can access and call the object through the Internet.
The following is the basic step of using Simple RMI:
1. Define the remote interface (Remote Interface):
First of all, we need to define a remote interface, which contains methods we want to call on remote objects.The interface should expand the `java.rmi.remote` interface and declare on each method.
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface MyRemoteInterface extends Remote {
// Definition of remote methods
public String sayHello() throws RemoteException;
}
2. Realize remote objects:
Next, we create a remote object class that implements remote interfaces.This class should be extended `java.rmi.server.UnicastremoteObject` and implement the method we define in remote interfaces.
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class MyRemoteObject extends UnicastRemoteObject implements MyRemoteInterface {
public MyRemoteObject() throws RemoteException {
// Construction method
}
public String sayHello() throws RemoteException {
return "Hello from remote object!";
}
}
3. Create RMI Registry (RMI Registry):
The RMI registry is a server -side component used by the Simple RMI framework to maintain remote objects.We need to create an RMI registry in a JVM to enable the remote objects to be accessed by other JVMs.You can create the RMI registry through the static method of the static method of the static method of the static method of the static method of the static method of the static method of the static method of the `java.rmi.regization.
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class RMIServer {
public static void main(String[] args) {
try {
// Create an RMI registry
Registry registry = LocateRegistry.createRegistry(1099);
// Create a remote object
MyRemoteObject remoteObj = new MyRemoteObject();
// Binded remote objects to the RMI registry
registry.bind("MyRemoteObj", remoteObj);
System.out.println("RMI Server is running...");
} catch (Exception e) {
e.printStackTrace();
}
}
}
4. Remote call:
As shown above, we have binded remote objects to the RMI registry.Now, we can use remote objects and call its method for remote calls in another JVM.
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class RMIClient {
public static void main(String[] args) {
try {
// Find the RMI registry
Registry registry = LocateRegistry.getRegistry("localhost");
// Find the remote object
MyRemoteInterface remoteObj = (MyRemoteInterface) registry.lookup("MyRemoteObj");
// Call the remote method
String result = remoteObj.sayHello();
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Through the above steps, we can easily use the Simple RMI framework to easily implement the remote method calls in the Java distributed system.
