java rmi

搬运维基百科的代码，已实际测试过。记录下一些注意事项

1. 远程服务接口需要继承 java.rmi.Remote 
2. 接口方法需要申明抛出java.rmi.RemoteException，
3. 接口方法参数或返回值的class类型需要实现序列化接口即java.io.Serializable或者为八种基本数据类型。
4. 远程调用时是通过序列化的方法传递数据，int类型可能会被转换为double类型
5. 远程调用参数或返回值的class类型必须两个jvm中都有。这里的class类型是实例的具体类型，而不是申明类型，匿名类，由spring框架切面生产的代理类都会报错。

 

下述代码仅为本地localhost测试，实际不同主机使用时，需要考虑权限问题。

package study.rmi;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface RmiServerIntf extends Remote {
  public String getMessage() throws RemoteException;

}

package study.rmi;

import java.rmi.Naming;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;

public class RmiServer extends UnicastRemoteObject implements RmiServerIntf {
  public static final String MESSAGE = "Hello World";

  public RmiServer() throws RemoteException {
    super(0);    // required to avoid the 'rmic' step, see below
  }

  @Override
  public String getMessage() {
    return MESSAGE;
  }

  public static void main(String args[]) throws Exception {
    System.out.println("RMI server started");

    try { //special exception handler for registry creation
      LocateRegistry.createRegistry(1099);
      System.out.println("java RMI registry created.");
    } catch (RemoteException e) {
      //do nothing, error means registry already exists
      System.out.println("java RMI registry already exists.");
    }

    //Instantiate RmiServer

    RmiServer obj = new RmiServer();

    // Bind this object instance to the name "RmiServer"
    Naming.rebind("//localhost/RmiServer", obj);
    System.out.println("PeerServer bound in registry");
  }
}

package study.rmi;

import java.rmi.Naming;

public class RmiClient {
  public static void main(String args[]) throws Exception {
    RmiServerIntf obj = (RmiServerIntf) Naming.lookup("//localhost/RmiServer");
    System.out.println(obj.getMessage());
  }
}