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import java.io.*; |
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import java.util.*; |
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import uk.ac.ukc.iscream.util.*; |
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// the plugin filter manager |
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// This is a singleton class. |
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// pjm2@ukc.ac.uk |
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class PluginFilterManager { |
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// public method to return an instance of a PluginFilterManager, |
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// as this class is a singleton. |
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public static PluginFilterManager init() throws AlreadyInitialisedException { |
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if (_instance != null){ |
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throw new AlreadyInitialisedException("init() has already been called."); |
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} |
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_instance = new PluginFilterManager(); |
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return _instance; |
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} |
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|
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// Return a reference to the single class. |
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public static PluginFilterManager getInstance() throws NotInitialisedException { |
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if (_instance == null){ |
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throw new NotInitialisedException("An instance of PluginFilterManager hasn't been initialised yet!"); |
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} |
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return _instance; |
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} |
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|
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// Private Constructor - this part creates the filter pipeline |
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// This is a singleton class, btw. |
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private PluginFilterManager(){ |
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System.out.println("Creating filter pipeline for plugin filters ..."); |
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// Look in the specified directory for "*__Plugin.class" files. |
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File file = new File(_directory); |
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String[] files = file.list(); |
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|
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// For each "__Plugin.class" file... |
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for (int i = 0; i < files.length; i++){ |
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if (files[i].endsWith(_suffix)){ |
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|
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// Remove the ".class" file extension. |
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files[i] = files[i].substring(0, files[i].length() - 6); |
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// Create an instance of the specified PluginFilter to include |
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// within the filterPipe. Add it to the filterPipeline |
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try { |
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PluginFilter pf = (PluginFilter)ClassLoader.getSystemClassLoader().loadClass(files[i]).newInstance(); |
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_filterPipeline.add(pf); |
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System.out.println("Added filter: "+files[i]); |
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} |
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catch (InstantiationException e){ |
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System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline."); |
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} |
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catch (Exception e){ |
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System.out.println("Failed to add "+files[i]+" to the plugin filter pipeline."); |
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} |
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|
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} |
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else { |
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//System.out.println("Ignoring "+files[i]+" in the plugin folder."); |
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} |
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} |
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System.out.println("The filter pipeline has been set up with "+_filterPipeline.size()+" plugin filters."); |
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|
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} |
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// apply all of the filters in the pipeline to the packet. |
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// return true if they all accept the packet. |
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// return false if any single filter rejects the packet. |
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// return true if there are no filters inthe pipeline. |
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public boolean runFilters(XMLPacket packet){ |
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|
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// for each filter in the pipeline... |
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ListIterator pluginFilters = _filterPipeline.listIterator(0); |
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while (pluginFilters.hasNext()){ |
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PluginFilter filter = (PluginFilter)pluginFilters.next(); |
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if (!filter.runFilter(packet)){ |
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return false; |
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} |
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} |
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return true; |
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} |
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// directory storing the plugins: |
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private final String _directory = "./"; |
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|
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// file name suffix for plugin filter classes: |
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private final String _suffix = "__Plugin.class"; |
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// LinkedList for holding the PluginFilter objects (the pipeline). |
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private LinkedList _filterPipeline = new LinkedList(); |
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// A reference to the single instance of this class |
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private static PluginFilterManager _instance; |
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|
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} |
