使用JAVA中RMI机制来实现分布式程序(2)

摘一段分布式系统中的例子代码：（http://www.cdk5.net/wp/extra-material/supplementary-material-for-chapter-5）

（但经过本人亲测，此代码还是有问题的，主要是涉及

 System.setSecurityManager(new RMISecurityManager());这句无法真正起作用，所以还是建议参看前两篇的文章中的方法！
）
这里最主要的学习点就是一旦完成了这种RMI机制，在服务器端和客户端可以实现callback的机制时，可以跨位置（进程）调用类。就是说如果服务器端
需要实例化一个客户端定义的类也是完全可以的，这个时候将在整个分布式系统中需要相应的类定义，所以可以讲客户端的代码“下载”到服务器端！

1：
package examples.RMIShape;
import java.rmi.*;
import java.util.Vector;

public interface Shape extends Remote {
   int getVersion() throws RemoteException;
   GraphicalObject getAllState() throws RemoteException;
}
2：

package examples.RMIShape;
import java.rmi.*;
import java.util.Vector;

public interface ShapeList extends Remote {
  	Shape newShape(GraphicalObject g) throws RemoteException;  	    
    Vector allShapes()throws RemoteException;
    int getVersion() throws RemoteException;
}
3：

package examples.RMIShape;
import java.rmi.*;
import java.rmi.server.UnicastRemoteObject;
public class ShapeListServer {
	public static void main(String args[]){
         System.setSecurityManager(new RMISecurityManager());
        try{
            ShapeList aShapelist = new ShapeListServant();
            ShapeList stub = (ShapeList) UnicastRemoteObject.exportObject(aShapeList,0);
			Naming.rebind("ShapeList", aShapelist); 
            System.out.println("ShapeList server ready");
        }catch(Exception e) {
            System.out.println("ShapeList server main " + e.getMessage());
        }
    }
}
:4：

package examples.RMIShape;
import java.util.Vector;
public class ShapeListServant implements ShapeList{
    private Vector theList;
    private int version;
    
    public ShapeListServant()throws RemoteException{
        theList = new Vector();
        version = 0;
    }

  	public Shape newShape(GraphicalObject g) throws RemoteException{
  	    version++;
       	Shape s = new ShapeServant( g, version);
        theList.addElement(s);                
        return s;
     }

   	public  Vector allShapes()throws RemoteException{
        return theList;
    }

    public int getVersion() throws RemoteException{
        return version;
    } 
}
:5：

package examples.RMIShape;
import java.rmi.*;
import java.rmi.server.UnicastRemoteObject;



public class ShapeServant extends UnicastRemoteObject implements Shape {
    int myVersion;
    GraphicalObject theG;
     
    public ShapeServant(GraphicalObject g, int version)throws RemoteException{
    	theG = g;
 		myVersion = version;
    }
    
    
	public int getVersion() throws RemoteException {
	    return myVersion;
	}
	
   public GraphicalObject  getAllState() throws RemoteException{
        return theG;
   }
    
}

6：

package examples.RMIShape;
import java.rmi.*;
import java.rmi.server.*;
import java.util.Vector;
import java.awt.Rectangle;
import java.awt.Color;


public class ShapeListClient{
   public static void main(String args[]){
   		String option = "Read";
		String shapeType = "Rectangle";
		if(args.length > 0)  option = args[0];	// read or write
		if(args.length > 1)  shapeType = args[1];	// specify Circle, Line etc
 		System.out.println("option = " + option + "shape = " + shapeType);
 		if(System.getSecurityManager() == null){
        	System.setSecurityManager(new RMISecurityManager());
        } else System.out.println("Already has a security manager, so cant set RMI SM");
        ShapeList aShapeList = null;
        try{
            aShapeList  = (ShapeList) Naming.lookup("//Jean.torriano.net/ShapeList");
 			System.out.println("Found server");
 			Vector sList = aShapeList.allShapes();
 			System.out.println("Got vector");
			if(option.equals("Read")){
				for(int i=0; i<sList.size(); i++){
        			GraphicalObject g = ((Shape)sList.elementAt(i)).getAllState();
        			g.print();
        		}
        	} else {
                GraphicalObject g = new GraphicalObject(shapeType, new Rectangle(50,50,300,400),Color.red,
                  			Color.blue, false);
                System.out.println("Created graphical object");
      					aShapeList.newShape(g);
      			System.out.println("Stored shape");
        	}
		}catch(RemoteException e) {System.out.println("allShapes: " + e.getMessage());
	    }catch(Exception e) {System.out.println("Lookup: " + e.getMessage());}
    }
}


:7：

package examples.RMIShape;

import java.awt.Rectangle;
import java.awt.Color;
import java.io.Serializable;
public class GraphicalObject implements Serializable{
    public String type;
    public Rectangle enclosing;
    public Color line;
    public Color fill;
    public boolean isFilled;
    
    //	constructors
    public GraphicalObject() { }
    
    public GraphicalObject(String aType, Rectangle anEnclosing, Color aLine,Color aFill, boolean anIsFilled) {
		type = aType;
		enclosing = anEnclosing;
		line = aLine;
		fill = aFill;
		isFilled = anIsFilled;
    }
    
    public void print(){
		System.out.print(type);
		System.out.print(enclosing.x + " , " + enclosing.y + " , " + enclosing.width + " , "  + enclosing.height);
		if(isFilled) System.out.println("- filled");else System.out.println("not filled");
	}
}