server/componentmanager/XMLCache.java

/* 
 * i-scream central monitoring system
 * http://www.i-scream.org
 * Copyright (C) 2000-2002 i-scream
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

//---PACKAGE DECLARATION---
package uk.org.iscream.cms.server.componentmanager;

//---IMPORTS---
import java.util.HashMap;
import uk.org.iscream.cms.util.*;
import uk.org.iscream.cms.server.core.*;

/**
 * An XMLCache to cut down the cost of XML parsing.
 * This class tries to ensure we only parse a String of XML
 * into an XML packet once.
 *
 * @author  $Author: tdb $
 * @version $Id: XMLCache.java,v 1.3 2003/02/05 16:43:46 tdb Exp $
 */
public class XMLCache extends Thread {

//---FINAL ATTRIBUTES---

    /**
     * The current CVS revision of this class
     */
    public static final String REVISION = "$Revision: 1.3 $";
    
    /**
     * The default period for cleaning out old XMLPackets
     */
    public final int DEFAULT_CLEANUP_PERIOD = 30;
    
//---STATIC METHODS---

    /**
     * Reference to our instance - we're a singleton.
     */
    private static XMLCache _instance;
    
    /**
     * Static initialiser block for constructing the initial
     * instance of this singleton.
     */
    static {
        _instance = new XMLCache();
    }
    
    /**
     * Return a reference to our singleton.
     */
    public static XMLCache getInstance() {
        return _instance;
    }
    
//---CONSTRUCTORS---

    /**
     * A private constructor to start this class up
     */
    private XMLCache() {
        // set the Thread name
        setName("componentmanager.XMLCache");
        // and start it
        start();
    }

//---PUBLIC METHODS---

    /**
     * Main loop for the thread to clean out old XMLPackets. This is
     * done by swapping HashMap's around. This seemed like the most
     * efficient approach, and is infact a documented garbage collection
     * technique :)
     */
    public void run() {
        while(_running) {
            // get cleanup period from configuration
            int cleanupPeriod = 0;
            try {
                cleanupPeriod = Integer.parseInt(ConfigurationProxy.getInstance().getProperty("XMLCache", "XMLCache.cleanupPeriod"));
            } catch (NumberFormatException e) {
                cleanupPeriod = DEFAULT_CLEANUP_PERIOD;
                _logger.write(toString(), Logger.WARNING, "Erronous XMLCache.cleanupPeriod value in configuration using default of " + cleanupPeriod + " seconds");
            } catch (PropertyNotFoundException e) {
                cleanupPeriod = DEFAULT_CLEANUP_PERIOD;
                _logger.write(toString(), Logger.WARNING, "XMLCache.cleanupPeriod value unavailable using default of " + cleanupPeriod + " seconds");
            }
            
            // wait for determined length of time
            try {
                Thread.sleep(cleanupPeriod * 1000);
            } catch (InterruptedException e) {
            }
            
            // do the swap
            synchronized (this) {
                _hashB = _hashA;
                // creating a new HashMap is quicker than clearing the old one
                _hashA = new HashMap();
            }
        }
    }

    /**
     * Overrides the {@link java.lang.Object#toString() Object.toString()}
     * method to provide clean logging (every class should have this).
     *
     * This uses the uk.org.iscream.cms.util.FormatName class
     * to format the toString()
     *
     * @return the name of this class and its CVS revision
     */
    public String toString() {
        return FormatName.getName(
            _name,
            getClass().getName(),
            REVISION);
    }

//---PRIVATE METHODS---

//---ACCESSOR/MUTATOR METHODS---

    /**
     * Generates an XMLPacket from a given String of XML, checking
     * to see if it already has the XMLPacket cached.
     *
     * @param xml A String of XML data
     * @return An XMLPacket representing the xml parameter
     * @throws InvalidXMLException if the XML does not parse
     */
    public XMLPacket getXMLPacket(String xml) throws InvalidXMLException {
        // Hash A is more likely to contain the result, assuming we have our
        // swap timing about right :)
        if(_hashA.containsKey(xml)) {
            return (XMLPacket) _hashA.get(xml);
        }
        else if(_hashB.containsKey(xml)) {
            return (XMLPacket) _hashB.get(xml);
        }
        else {
            XMLPacket packet = _xmlPacketMaker.createXMLPacket(xml);
            // always add to hash A
            _hashA.put(xml, packet);
            return packet;
        }
    }

//---ATTRIBUTES---

    // think about initial parameters for HashMap's
    
    /**
     * Our primary HashMap
     */
    private HashMap _hashA = new HashMap();
    
    /**
     * Our secondary HashMap
     */
    private HashMap _hashB = new HashMap();

    /**
     * A reference to an XMLPacketMaker which we can use
     * to generate XMLPackets from XML Strings
     */
    private XMLPacketMaker _xmlPacketMaker = new XMLPacketMaker();

    /**
     * We can set this to false to stop the Thread
     */
    private boolean _running = true;

    /**
     * This is the friendly identifier of the
     * component this class is running in.
     * eg, a Filter may be called "filter1",
     * If this class does not have an owning
     * component,  a name from the configuration
     * can be placed here.  This name could also
     * be changed to null for utility classes.
     */
    private String _name = null;

    /**
     * This holds a reference to the
     * system logger that is being used.
     */
    private Logger _logger = ReferenceManager.getInstance().getLogger();

//---STATIC ATTRIBUTES---

}
Revision:	1.4
Committed:	Sun Aug 1 10:40:50 2004 UTC (19 years, 9 months ago) by tdb
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.3:	+3 -3 lines
Log Message:	Catch a lot of old URL's and update them. Also remove a couple of old files that aren't used.
#	User	Rev	Content
1	tdb	1.1	/*
2			* i-scream central monitoring system
3	tdb	1.4	* http://www.i-scream.org
4	tdb	1.1	* Copyright (C) 2000-2002 i-scream
5			*
6			* This program is free software; you can redistribute it and/or
7			* modify it under the terms of the GNU General Public License
8			* as published by the Free Software Foundation; either version 2
9			* of the License, or (at your option) any later version.
10			*
11			* This program is distributed in the hope that it will be useful,
12			* but WITHOUT ANY WARRANTY; without even the implied warranty of
13			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14			* GNU General Public License for more details.
15			*
16			* You should have received a copy of the GNU General Public License
17			* along with this program; if not, write to the Free Software
18			* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19			*/
20
21			//---PACKAGE DECLARATION---
22			package uk.org.iscream.cms.server.componentmanager;
23
24			//---IMPORTS---
25			import java.util.HashMap;
26	tdb	1.3	import uk.org.iscream.cms.util.*;
27	tdb	1.1	import uk.org.iscream.cms.server.core.*;
28
29			/**
30			* An XMLCache to cut down the cost of XML parsing.
31			* This class tries to ensure we only parse a String of XML
32			* into an XML packet once.
33			*
34	tdb	1.2	* @author $Author: tdb $
35	tdb	1.4	* @version $Id: XMLCache.java,v 1.3 2003/02/05 16:43:46 tdb Exp $
36	tdb	1.1	*/
37	tdb	1.2	public class XMLCache extends Thread {
38	tdb	1.1
39			//---FINAL ATTRIBUTES---
40
41			/**
42			* The current CVS revision of this class
43			*/
44	tdb	1.4	public static final String REVISION = "$Revision: 1.3 $";
45	tdb	1.1
46			/**
47			* The default period for cleaning out old XMLPackets
48			*/
49			public final int DEFAULT_CLEANUP_PERIOD = 30;
50
51			//---STATIC METHODS---
52
53			/**
54			* Reference to our instance - we're a singleton.
55			*/
56			private static XMLCache _instance;
57
58			/**
59			* Static initialiser block for constructing the initial
60			* instance of this singleton.
61			*/
62			static {
63			_instance = new XMLCache();
64			}
65
66			/**
67			* Return a reference to our singleton.
68			*/
69			public static XMLCache getInstance() {
70			return _instance;
71			}
72
73			//---CONSTRUCTORS---
74
75			/**
76			* A private constructor to start this class up
77			*/
78			private XMLCache() {
79			// set the Thread name
80			setName("componentmanager.XMLCache");
81			// and start it
82			start();
83			}
84
85			//---PUBLIC METHODS---
86
87			/**
88			* Main loop for the thread to clean out old XMLPackets. This is
89			* done by swapping HashMap's around. This seemed like the most
90			* efficient approach, and is infact a documented garbage collection
91			* technique :)
92			*/
93			public void run() {
94			while(_running) {
95			// get cleanup period from configuration
96			int cleanupPeriod = 0;
97			try {
98			cleanupPeriod = Integer.parseInt(ConfigurationProxy.getInstance().getProperty("XMLCache", "XMLCache.cleanupPeriod"));
99			} catch (NumberFormatException e) {
100			cleanupPeriod = DEFAULT_CLEANUP_PERIOD;
101			_logger.write(toString(), Logger.WARNING, "Erronous XMLCache.cleanupPeriod value in configuration using default of " + cleanupPeriod + " seconds");
102			} catch (PropertyNotFoundException e) {
103			cleanupPeriod = DEFAULT_CLEANUP_PERIOD;
104			_logger.write(toString(), Logger.WARNING, "XMLCache.cleanupPeriod value unavailable using default of " + cleanupPeriod + " seconds");
105			}
106
107			// wait for determined length of time
108			try {
109			Thread.sleep(cleanupPeriod * 1000);
110			} catch (InterruptedException e) {
111			}
112
113			// do the swap
114			synchronized (this) {
115			_hashB = _hashA;
116			// creating a new HashMap is quicker than clearing the old one
117			_hashA = new HashMap();
118			}
119			}
120			}
121
122			/**
123			* Overrides the {@link java.lang.Object#toString() Object.toString()}
124			* method to provide clean logging (every class should have this).
125			*
126	tdb	1.3	* This uses the uk.org.iscream.cms.util.FormatName class
127	tdb	1.1	* to format the toString()
128			*
129			* @return the name of this class and its CVS revision
130			*/
131			public String toString() {
132			return FormatName.getName(
133			_name,
134			getClass().getName(),
135			REVISION);
136			}
137
138			//---PRIVATE METHODS---
139
140			//---ACCESSOR/MUTATOR METHODS---
141
142			/**
143			* Generates an XMLPacket from a given String of XML, checking
144			* to see if it already has the XMLPacket cached.
145			*
146			* @param xml A String of XML data
147			* @return An XMLPacket representing the xml parameter
148			* @throws InvalidXMLException if the XML does not parse
149			*/
150			public XMLPacket getXMLPacket(String xml) throws InvalidXMLException {
151			// Hash A is more likely to contain the result, assuming we have our
152			// swap timing about right :)
153			if(_hashA.containsKey(xml)) {
154			return (XMLPacket) _hashA.get(xml);
155			}
156			else if(_hashB.containsKey(xml)) {
157			return (XMLPacket) _hashB.get(xml);
158			}
159			else {
160			XMLPacket packet = _xmlPacketMaker.createXMLPacket(xml);
161			// always add to hash A
162			_hashA.put(xml, packet);
163			return packet;
164			}
165			}
166
167			//---ATTRIBUTES---
168
169			// think about initial parameters for HashMap's
170
171			/**
172			* Our primary HashMap
173			*/
174			private HashMap _hashA = new HashMap();
175
176			/**
177			* Our secondary HashMap
178			*/
179			private HashMap _hashB = new HashMap();
180
181			/**
182			* A reference to an XMLPacketMaker which we can use
183			* to generate XMLPackets from XML Strings
184			*/
185			private XMLPacketMaker _xmlPacketMaker = new XMLPacketMaker();
186
187			/**
188			* We can set this to false to stop the Thread
189			*/
190			private boolean _running = true;
191
192			/**
193			* This is the friendly identifier of the
194			* component this class is running in.
195			* eg, a Filter may be called "filter1",
196			* If this class does not have an owning
197			* component, a name from the configuration
198			* can be placed here. This name could also
199			* be changed to null for utility classes.
200			*/
201			private String _name = null;
202
203			/**
204			* This holds a reference to the
205			* system logger that is being used.
206			*/
207			private Logger _logger = ReferenceManager.getInstance().getLogger();
208
209			//---STATIC ATTRIBUTES---
210
211			}