server/PluginManager/PluginFilterManager.java

import java.io.*;
import java.util.*;

import uk.ac.ukc.iscream.util.*;

// the plugin filter manager
// This is a singleton class.

// pjm2@ukc.ac.uk

class PluginFilterManager {
    
    // public method to return an instance of a PluginFilterManager,
    // as this class is a singleton.
    public static PluginFilterManager init() throws AlreadyInitialisedException { 
        if (_instance != null){
            throw new AlreadyInitialisedException("init() has already been called.");
        }
        _instance = new PluginFilterManager();
        return _instance;
    }
    
    // Return a reference to the single class.
    public static PluginFilterManager getInstance() throws NotInitialisedException {
        if (_instance == null){
            throw new NotInitialisedException("An instance of PluginFilterManager hasn't been initialised yet!");
        }
        return _instance;
    }
    
    // Private Constructor - this part creates the filter pipeline
    // This is a singleton class, btw.
    private PluginFilterManager(){
        
        System.out.println("Creating filter pipeline for plugin filters ...");
        
        // Look in the specified directory for "*__Plugin.class" files.
        File file = new File(_directory);
        String[] files = file.list();
        
        // For each "__Plugin.class" file...
        for (int i = 0; i < files.length; i++){
            if (files[i].endsWith(_suffix)){
                
                // Remove the ".class" file extension.
                files[i] = files[i].substring(0, files[i].length() - 6);
                
                // Create an instance of the specified PluginFilter to include
                // within the filterPipe.  Add it to the filterPipeline
                try {
                    PluginFilter pf = (PluginFilter)ClassLoader.getSystemClassLoader().loadClass(files[i]).newInstance();
                    _filterPipeline.add(pf);
                    System.out.println("Added filter: "+files[i]);
                }
                catch (InstantiationException e){
                    System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline.");
                }
                catch (Exception e){
                    System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline.");
                }
                
            }
            else {
                //System.out.println("Ignoring "+files[i]+" in the plugin folder.");
            }
        }
        
        System.out.println("The filter pipeline has been set up with "+_filterPipeline.size()+" plugin filters.");
        
    }
    
    
    // apply all of the filters in the pipeline to the packet.
    // return true if they all accept the packet.
    // return false if any single filter rejects the packet.
    // return true if there are no filters inthe pipeline.
    public boolean runFilters(XMLPacket packet){
        
        // for each filter in the pipeline...
        ListIterator pluginFilters = _filterPipeline.listIterator(0);
        while (pluginFilters.hasNext()){
            PluginFilter filter = (PluginFilter)pluginFilters.next();
            if (!filter.runFilter(packet)){
                return false;
            }
        }
        
        return true;
    }
    
    
    // directory storing the plugins:
    private final String _directory = "./";
    
    // file name suffix for plugin filter classes:
    private final String _suffix = "__Plugin.class";
    
    // LinkedList for holding the PluginFilter objects (the pipeline).
    private LinkedList _filterPipeline = new LinkedList();
    
    // A reference to the single instance of this class
    private static PluginFilterManager _instance;
    
}
Revision:	1.2
Committed:	Fri Dec 1 09:51:32 2000 UTC (23 years, 5 months ago) by pjm2
Branch:	MAIN
Changes since 1.1:	+1 -1 lines
Log Message:	How did that "-" get there at the end?!
#	User	Rev	Content
1	pjm2	1.1	import java.io.*;
2			import java.util.*;
3
4			import uk.ac.ukc.iscream.util.*;
5
6			// the plugin filter manager
7			// This is a singleton class.
8
9			// pjm2@ukc.ac.uk
10
11			class PluginFilterManager {
12
13			// public method to return an instance of a PluginFilterManager,
14			// as this class is a singleton.
15			public static PluginFilterManager init() throws AlreadyInitialisedException {
16			if (_instance != null){
17			throw new AlreadyInitialisedException("init() has already been called.");
18			}
19			_instance = new PluginFilterManager();
20			return _instance;
21			}
22
23			// Return a reference to the single class.
24			public static PluginFilterManager getInstance() throws NotInitialisedException {
25			if (_instance == null){
26			throw new NotInitialisedException("An instance of PluginFilterManager hasn't been initialised yet!");
27			}
28			return _instance;
29			}
30
31			// Private Constructor - this part creates the filter pipeline
32			// This is a singleton class, btw.
33			private PluginFilterManager(){
34
35			System.out.println("Creating filter pipeline for plugin filters ...");
36
37			// Look in the specified directory for "*__Plugin.class" files.
38			File file = new File(_directory);
39			String[] files = file.list();
40
41			// For each "__Plugin.class" file...
42			for (int i = 0; i < files.length; i++){
43			if (files[i].endsWith(_suffix)){
44
45			// Remove the ".class" file extension.
46			files[i] = files[i].substring(0, files[i].length() - 6);
47
48			// Create an instance of the specified PluginFilter to include
49			// within the filterPipe. Add it to the filterPipeline
50			try {
51			PluginFilter pf = (PluginFilter)ClassLoader.getSystemClassLoader().loadClass(files[i]).newInstance();
52			_filterPipeline.add(pf);
53			System.out.println("Added filter: "+files[i]);
54			}
55			catch (InstantiationException e){
56			System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline.");
57			}
58			catch (Exception e){
59			System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline.");
60			}
61
62			}
63			else {
64			//System.out.println("Ignoring "+files[i]+" in the plugin folder.");
65			}
66			}
67
68			System.out.println("The filter pipeline has been set up with "+_filterPipeline.size()+" plugin filters.");
69
70			}
71
72
73			// apply all of the filters in the pipeline to the packet.
74			// return true if they all accept the packet.
75			// return false if any single filter rejects the packet.
76			// return true if there are no filters inthe pipeline.
77			public boolean runFilters(XMLPacket packet){
78
79			// for each filter in the pipeline...
80			ListIterator pluginFilters = _filterPipeline.listIterator(0);
81			while (pluginFilters.hasNext()){
82			PluginFilter filter = (PluginFilter)pluginFilters.next();
83			if (!filter.runFilter(packet)){
84			return false;
85			}
86			}
87
88			return true;
89			}
90
91
92			// directory storing the plugins:
93			private final String _directory = "./";
94
95			// file name suffix for plugin filter classes:
96			private final String _suffix = "__Plugin.class";
97
98			// LinkedList for holding the PluginFilter objects (the pipeline).
99			private LinkedList _filterPipeline = new LinkedList();
100
101			// A reference to the single instance of this class
102			private static PluginFilterManager _instance;
103
104	pjm2	1.2	}