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 writeif(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");}}