1   /*
2    * Created on May 13, 2004
3    *
4    */
5   
6   package functional.agent;
7   
8   import java.util.Collection;
9   import java.util.HashSet;
10  import java.util.Iterator;
11  import java.util.Set;
12  
13  import org.neo.swarm.ApplicationContext;
14  import org.neo.swarm.SwarmContainer;
15  
16  /***
17   * Represents an Agent that travels to all ApplicationContexts and displays the set of visited URIs upon exiting. 
18   * Note: Mobile agents rely on the AppContextBinding interface to gain a reference to the local application
19   * context, which in turn provides the ability to access all container components and services.
20   * @author navery
21   */
22  public class MobileAgentImpl implements MobileAgent {
23  
24  	public String name = "MobileAgent";
25  	ApplicationContext ac;
26  	String currentURI;
27  	Set visited = new HashSet();
28  	
29  	/***
30  	 * Determines where to next..
31  	 */
32  	public void execute() {
33  		try {
34  			System.out.println("Executing: Agent:" + this.name + " context:" + this.currentURI);
35  			
36  			SwarmContainer container = (SwarmContainer) this.ac.retrieveComponent("container");
37  			
38  			// get a list of URIs from the Container
39  			Collection appContexts = container.getComponentsOfType(ApplicationContext.class);
40  
41  			// chose one that hasnt been visted before
42  			Iterator iter = appContexts.iterator();
43  			while (iter.hasNext()){
44  				ApplicationContext newAC = (ApplicationContext) iter.next();
45  				String acID = newAC.getURI();
46  				if (!visited.contains(acID)){
47  					this.visit(acID, newAC);
48  					break;
49  				}
50  			}
51  			System.out.println("Agent exiting = this instance visited:" + this.visited);
52  		} catch (Exception e) {
53  			e.printStackTrace();
54  		}
55  	}
56  
57  	/***
58  	 * Relocates Agent to the chosen node.
59  	 * @param newURI
60  	 */
61  	public void visit(String newURI, ApplicationContext newAC) {
62  		System.out.println("Agent about to shift to:"+newURI);
63  		
64  		visited.add(newURI);
65  
66  		// inject ourself into the remote AppContext
67  		newAC.addPreConstructedComponent(this.name, this);
68  
69  		// get remote handle to new instance
70  		MobileAgent remoteAgent = (MobileAgent) newAC.retrieveComponent(this.name);
71  		
72  		// tell it to carry on executing in the new context
73  		remoteAgent.execute();
74  
75  		// dissapear...
76  		this.ac.removeComponent(this.name);
77  	}
78  
79  	/* (non-Javadoc)
80  	 * @see org.neo.swarm.AppContextBinding#bind(org.neo.swarm.ApplicationContext)
81  	 */
82  	public void bind(ApplicationContext context) {
83  		System.out.println("Agent being injected into appContext:"+this.currentURI);
84  		this.ac = context;
85  		this.currentURI = context.getURI();
86  	}
87  }