RMI的使用

 RMI(Remote Method Invocation)系统由以下几个部分组成:

运行过程服务的服务器

需要过程服务的客户端程序

过程服务的接口定义

远程服务的实现

RMI命名服务,使得客户端可以发现远程服务

示例程序:

远程接口:

Task.java

import java.io.Serializable;
public interface Task extends Serializable {
 
 Object execute();
}

Compute.java

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

public interface Compute extends Remote {

 Object executeTask(Task t)throws RemoteException;
}

服务器:ComputeEngine.java

import java.rmi.*;
import java.rmi.server.*;
//import compute.*;
public class ComputeEngine extends UnicastRemoteObject implements Compute{

 public ComputeEngine() throws RemoteException
 {
  super();
 }
 public Object executeTask(Task t)
 {
  return t.execute();
 }
 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub

  if (System.getSecurityManager() == null)
  {
   System.setSecurityManager(new RMISecurityManager());
  }
  String name = "rmi://162.105.146.223/Compute";
  try {
   Compute engine = new ComputeEngine();
   Naming.rebind(name, engine);
   System.out.println("ComputeEngine bound");
  } catch (Exception e)
  {
   System.err.println("ComputeEngine exception: "
    + e.getMessage());
   e.printStackTrace(); 
  }
 }

}

客户端:

 Add.java

public class Add implements Task {

 //int a,b;
 //public Add(int i, int j)
 public Add()
 {
  //this.a = i;
  //this.b = j;
 }
 public Object execute() {
  // TODO Auto-generated method stub
  return 2;
 }

}

ComputeAdd.java

import java.rmi.*;
//import compute.*;
public class ComputeAdd {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub

  
  if (System.getSecurityManager() == null)
  {
   System.setSecurityManager(new RMISecurityManager());
   
  }
  
  try {
   String name = "//162.105.146.223" + "/Compute";
   Compute comp = (Compute) Naming.lookup(name);
   int a,b;
   a = 5;
   b = 10;
   Add task = new Add();
   int result = (Integer) (comp.executeTask(task));
   System.out.println(result);
  } catch (Exception e) {
   System.err.println("ComputeAdd exception: " + e.getMessage());
   e.printStackTrace();
  }
 }

}

运行步骤:

编译接口:
javac compute/Compute.java compute/Task.java
jar cvf compute.jar compute/*.class

将编译好的compute.jar放到apache目录下

编译服务器端:
javac -cp "D:/Program Files/apache2.2/htdocs/classes/compute.jar"
    engine/ComputeEngine.java

策略文件:
policy.txt
1.start rmiregistry

2.start java -cp e:/zhangyan/java/compute;"d:/Program Files/apache2.2/htdocs/classes/compute.jar" -Djava.rmi.server.codebase=http://127.0.0.1/classes/compute.jar -Djava.rmi.server.hostname=localhost -Djava.security.policy=server.policy engine.server

3.java -cp e:/zhangyan/java/compute;"d:/Program Files/apache2.2/htdocs/classes/compute.jar" -Djava.rmi.server.codebase=http://127.0.0.1/classes/ -Djava.security.policy=server.policy client.ComputeAdd localhost