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Tomcat example source code file (StringCache.java)

This example Tomcat source code file (StringCache.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

arraylist, arraylist, bytechunk, byteentry, byteentry, charentry, charentry, hashmap, integer, iterator, object, string, string, treemap, util

The Tomcat StringCache.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.util.buf;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.TreeMap;

/**
 * This class implements a String cache for ByteChunk and CharChunk.
 *
 * @author Remy Maucherat
 */
public class StringCache {


    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog( StringCache.class );
    
    
    // ------------------------------------------------------- Static Variables

    
    /**
     * Enabled ?
     */
    protected static boolean byteEnabled = 
        ("true".equals(System.getProperty("tomcat.util.buf.StringCache.byte.enabled", "false")));

    
    protected static boolean charEnabled = 
        ("true".equals(System.getProperty("tomcat.util.buf.StringCache.char.enabled", "false")));

    
    protected static int trainThreshold = 
        Integer.parseInt(System.getProperty("tomcat.util.buf.StringCache.trainThreshold", "20000"));
    

    protected static int cacheSize = 
        Integer.parseInt(System.getProperty("tomcat.util.buf.StringCache.cacheSize", "200"));
    

    protected static int maxStringSize = 
        Integer.parseInt(System.getProperty("tomcat.util.buf.StringCache.maxStringSize", "128"));
    

   /**
     * Statistics hash map for byte chunk.
     */
    protected static HashMap bcStats = new HashMap(cacheSize);

    
    /**
     * toString count for byte chunk.
     */
    protected static int bcCount = 0;
    
    
    /**
     * Cache for byte chunk.
     */
    protected static ByteEntry[] bcCache = null;
    

    /**
     * Statistics hash map for char chunk.
     */
    protected static HashMap ccStats = new HashMap(cacheSize);


    /**
     * toString count for char chunk.
     */
    protected static int ccCount = 0; 
    

    /**
     * Cache for char chunk.
     */
    protected static CharEntry[] ccCache = null;

    
    /**
     * Access count.
     */
    protected static int accessCount = 0;
    

    /**
     * Hit count.
     */
    protected static int hitCount = 0;
    

    // ------------------------------------------------------------ Properties

    
    /**
     * @return Returns the cacheSize.
     */
    public int getCacheSize() {
        return cacheSize;
    }
    
    
    /**
     * @param cacheSize The cacheSize to set.
     */
    public void setCacheSize(int cacheSize) {
        StringCache.cacheSize = cacheSize;
    }

    
    /**
     * @return Returns the enabled.
     */
    public boolean getByteEnabled() {
        return byteEnabled;
    }
    
    
    /**
     * @param byteEnabled The enabled to set.
     */
    public void setByteEnabled(boolean byteEnabled) {
        StringCache.byteEnabled = byteEnabled;
    }
    
    
    /**
     * @return Returns the enabled.
     */
    public boolean getCharEnabled() {
        return charEnabled;
    }
    
    
    /**
     * @param charEnabled The enabled to set.
     */
    public void setCharEnabled(boolean charEnabled) {
        StringCache.charEnabled = charEnabled;
    }
    
    
    /**
     * @return Returns the trainThreshold.
     */
    public int getTrainThreshold() {
        return trainThreshold;
    }
    
    
    /**
     * @param trainThreshold The trainThreshold to set.
     */
    public void setTrainThreshold(int trainThreshold) {
        StringCache.trainThreshold = trainThreshold;
    }

    
    /**
     * @return Returns the accessCount.
     */
    public int getAccessCount() {
        return accessCount;
    }
    
    
    /**
     * @return Returns the hitCount.
     */
    public int getHitCount() {
        return hitCount;
    }

    
    // -------------------------------------------------- Public Static Methods

    
    public void reset() {
        hitCount = 0;
        accessCount = 0;
        synchronized (bcStats) {
            bcCache = null;
            bcCount = 0;
        }
        synchronized (ccStats) {
            ccCache = null;
            ccCount = 0;
        }
    }
    
    
    public static String toString(ByteChunk bc) {

        // If the cache is null, then either caching is disabled, or we're
        // still training
        if (bcCache == null) {
            String value = bc.toStringInternal();
            if (byteEnabled && (value.length() < maxStringSize)) {
                // If training, everything is synced
                synchronized (bcStats) {
                    // If the cache has been generated on a previous invocation
                    // while waiting fot the lock, just return the toString value
                    // we just calculated
                    if (bcCache != null) {
                        return value;
                    }
                    // Two cases: either we just exceeded the train count, in which
                    // case the cache must be created, or we just update the count for
                    // the string
                    if (bcCount > trainThreshold) {
                        long t1 = System.currentTimeMillis();
                        // Sort the entries according to occurrence
                        TreeMap tempMap = new TreeMap();
                        Iterator entries = bcStats.keySet().iterator();
                        while (entries.hasNext()) {
                            ByteEntry entry = (ByteEntry) entries.next();
                            int[] countA = (int[]) bcStats.get(entry);
                            Integer count = new Integer(countA[0]);
                            // Add to the list for that count
                            ArrayList list = (ArrayList) tempMap.get(count);
                            if (list == null) {
                                // Create list
                                list = new ArrayList();
                                tempMap.put(count, list);
                            }
                            list.add(entry);
                        }
                        // Allocate array of the right size
                        int size = bcStats.size();
                        if (size > cacheSize) {
                            size = cacheSize;
                        }
                        ByteEntry[] tempbcCache = new ByteEntry[size];
                        // Fill it up using an alphabetical order
                        // and a dumb insert sort
                        ByteChunk tempChunk = new ByteChunk();
                        int n = 0;
                        while (n < size) {
                            Object key = tempMap.lastKey();
                            ArrayList list = (ArrayList) tempMap.get(key);
                            ByteEntry[] list2 = 
                                (ByteEntry[]) list.toArray(new ByteEntry[list.size()]);
                            for (int i = 0; i < list.size() && n < size; i++) {
                                ByteEntry entry = (ByteEntry) list.get(i);
                                tempChunk.setBytes(entry.name, 0, entry.name.length);
                                int insertPos = findClosest(tempChunk, tempbcCache, n);
                                if (insertPos == n) {
                                    tempbcCache[n + 1] = entry;
                                } else {
                                    System.arraycopy(tempbcCache, insertPos + 1, tempbcCache, 
                                            insertPos + 2, n - insertPos - 1);
                                    tempbcCache[insertPos + 1] = entry;
                                }
                                n++;
                            }
                            tempMap.remove(key);
                        }
                        bcCount = 0;
                        bcStats.clear();
                        bcCache = tempbcCache;
                        if (log.isDebugEnabled()) {
                            long t2 = System.currentTimeMillis();
                            log.debug("ByteCache generation time: " + (t2 - t1) + "ms");
                        }
                    } else {
                        bcCount++;
                        // Allocate new ByteEntry for the lookup
                        ByteEntry entry = new ByteEntry();
                        entry.value = value;
                        int[] count = (int[]) bcStats.get(entry);
                        if (count == null) {
                            int end = bc.getEnd();
                            int start = bc.getStart();
                            // Create byte array and copy bytes
                            entry.name = new byte[bc.getLength()];
                            System.arraycopy(bc.getBuffer(), start, entry.name, 0, end - start);
                            // Set encoding
                            entry.enc = bc.getEncoding();
                            // Initialize occurrence count to one 
                            count = new int[1];
                            count[0] = 1;
                            // Set in the stats hash map
                            bcStats.put(entry, count);
                        } else {
                            count[0] = count[0] + 1;
                        }
                    }
                }
            }
            return value;
        } else {
            accessCount++;
            // Find the corresponding String
            String result = find(bc);
            if (result == null) {
                return bc.toStringInternal();
            }
            // Note: We don't care about safety for the stats
            hitCount++;
            return result;
        }
        
    }


    public static String toString(CharChunk cc) {
        
        // If the cache is null, then either caching is disabled, or we're
        // still training
        if (ccCache == null) {
            String value = cc.toStringInternal();
            if (charEnabled && (value.length() < maxStringSize)) {
                // If training, everything is synced
                synchronized (ccStats) {
                    // If the cache has been generated on a previous invocation
                    // while waiting fot the lock, just return the toString value
                    // we just calculated
                    if (ccCache != null) {
                        return value;
                    }
                    // Two cases: either we just exceeded the train count, in which
                    // case the cache must be created, or we just update the count for
                    // the string
                    if (ccCount > trainThreshold) {
                        long t1 = System.currentTimeMillis();
                        // Sort the entries according to occurrence
                        TreeMap tempMap = new TreeMap();
                        Iterator entries = ccStats.keySet().iterator();
                        while (entries.hasNext()) {
                            CharEntry entry = (CharEntry) entries.next();
                            int[] countA = (int[]) ccStats.get(entry);
                            Integer count = new Integer(countA[0]);
                            // Add to the list for that count
                            ArrayList list = (ArrayList) tempMap.get(count);
                            if (list == null) {
                                // Create list
                                list = new ArrayList();
                                tempMap.put(count, list);
                            }
                            list.add(entry);
                        }
                        // Allocate array of the right size
                        int size = ccStats.size();
                        if (size > cacheSize) {
                            size = cacheSize;
                        }
                        CharEntry[] tempccCache = new CharEntry[size];
                        // Fill it up using an alphabetical order
                        // and a dumb insert sort
                        CharChunk tempChunk = new CharChunk();
                        int n = 0;
                        while (n < size) {
                            Object key = tempMap.lastKey();
                            ArrayList list = (ArrayList) tempMap.get(key);
                            CharEntry[] list2 = 
                                (CharEntry[]) list.toArray(new CharEntry[list.size()]);
                            for (int i = 0; i < list.size() && n < size; i++) {
                                CharEntry entry = (CharEntry) list.get(i);
                                tempChunk.setChars(entry.name, 0, entry.name.length);
                                int insertPos = findClosest(tempChunk, tempccCache, n);
                                if (insertPos == n) {
                                    tempccCache[n + 1] = entry;
                                } else {
                                    System.arraycopy(tempccCache, insertPos + 1, tempccCache, 
                                            insertPos + 2, n - insertPos - 1);
                                    tempccCache[insertPos + 1] = entry;
                                }
                                n++;
                            }
                            tempMap.remove(key);
                        }
                        ccCount = 0;
                        ccStats.clear();
                        ccCache = tempccCache;
                        if (log.isDebugEnabled()) {
                            long t2 = System.currentTimeMillis();
                            log.debug("CharCache generation time: " + (t2 - t1) + "ms");
                        }
                    } else {
                        ccCount++;
                        // Allocate new CharEntry for the lookup
                        CharEntry entry = new CharEntry();
                        entry.value = value;
                        int[] count = (int[]) ccStats.get(entry);
                        if (count == null) {
                            int end = cc.getEnd();
                            int start = cc.getStart();
                            // Create char array and copy chars
                            entry.name = new char[cc.getLength()];
                            System.arraycopy(cc.getBuffer(), start, entry.name, 0, end - start);
                            // Initialize occurrence count to one 
                            count = new int[1];
                            count[0] = 1;
                            // Set in the stats hash map
                            ccStats.put(entry, count);
                        } else {
                            count[0] = count[0] + 1;
                        }
                    }
                }
            }
            return value;
        } else {
            accessCount++;
            // Find the corresponding String
            String result = find(cc);
            if (result == null) {
                return cc.toStringInternal();
            }
            // Note: We don't care about safety for the stats
            hitCount++;
            return result;
        }
        
    }
    
    
    // ----------------------------------------------------- Protected Methods


    /**
     * Compare given byte chunk with byte array.
     * Return -1, 0 or +1 if inferior, equal, or superior to the String.
     */
    protected static final int compare(ByteChunk name, byte[] compareTo) {
        int result = 0;

        byte[] b = name.getBuffer();
        int start = name.getStart();
        int end = name.getEnd();
        int len = compareTo.length;

        if ((end - start) < len) {
            len = end - start;
        }
        for (int i = 0; (i < len) && (result == 0); i++) {
            if (b[i + start] > compareTo[i]) {
                result = 1;
            } else if (b[i + start] < compareTo[i]) {
                result = -1;
            }
        }
        if (result == 0) {
            if (compareTo.length > (end - start)) {
                result = -1;
            } else if (compareTo.length < (end - start)) {
                result = 1;
            }
        }
        return result;
    }

    
    /**
     * Find an entry given its name in the cache and return the associated String.
     */
    protected static final String find(ByteChunk name) {
        int pos = findClosest(name, bcCache, bcCache.length);
        if ((pos < 0) || (compare(name, bcCache[pos].name) != 0)
                || !(name.getEncoding().equals(bcCache[pos].enc))) {
            return null;
        } else {
            return bcCache[pos].value;
        }
    }

    
    /**
     * Find an entry given its name in a sorted array of map elements.
     * This will return the index for the closest inferior or equal item in the
     * given array.
     */
    protected static final int findClosest(ByteChunk name, ByteEntry[] array, int len) {

        int a = 0;
        int b = len - 1;

        // Special cases: -1 and 0
        if (b == -1) {
            return -1;
        }
        
        if (compare(name, array[0].name) < 0) {
            return -1;
        }         
        if (b == 0) {
            return 0;
        }

        int i = 0;
        while (true) {
            i = (b + a) / 2;
            int result = compare(name, array[i].name);
            if (result == 1) {
                a = i;
            } else if (result == 0) {
                return i;
            } else {
                b = i;
            }
            if ((b - a) == 1) {
                int result2 = compare(name, array[b].name);
                if (result2 < 0) {
                    return a;
                } else {
                    return b;
                }
            }
        }

    }


    /**
     * Compare given char chunk with char array.
     * Return -1, 0 or +1 if inferior, equal, or superior to the String.
     */
    protected static final int compare(CharChunk name, char[] compareTo) {
        int result = 0;

        char[] c = name.getBuffer();
        int start = name.getStart();
        int end = name.getEnd();
        int len = compareTo.length;

        if ((end - start) < len) {
            len = end - start;
        }
        for (int i = 0; (i < len) && (result == 0); i++) {
            if (c[i + start] > compareTo[i]) {
                result = 1;
            } else if (c[i + start] < compareTo[i]) {
                result = -1;
            }
        }
        if (result == 0) {
            if (compareTo.length > (end - start)) {
                result = -1;
            } else if (compareTo.length < (end - start)) {
                result = 1;
            }
        }
        return result;
    }

    
    /**
     * Find an entry given its name in the cache and return the associated String.
     */
    protected static final String find(CharChunk name) {
        int pos = findClosest(name, ccCache, ccCache.length);
        if ((pos < 0) || (compare(name, ccCache[pos].name) != 0)) {
            return null;
        } else {
            return ccCache[pos].value;
        }
    }

    
    /**
     * Find an entry given its name in a sorted array of map elements.
     * This will return the index for the closest inferior or equal item in the
     * given array.
     */
    protected static final int findClosest(CharChunk name, CharEntry[] array, int len) {

        int a = 0;
        int b = len - 1;

        // Special cases: -1 and 0
        if (b == -1) {
            return -1;
        }
        
        if (compare(name, array[0].name) < 0 ) {
            return -1;
        }         
        if (b == 0) {
            return 0;
        }

        int i = 0;
        while (true) {
            i = (b + a) / 2;
            int result = compare(name, array[i].name);
            if (result == 1) {
                a = i;
            } else if (result == 0) {
                return i;
            } else {
                b = i;
            }
            if ((b - a) == 1) {
                int result2 = compare(name, array[b].name);
                if (result2 < 0) {
                    return a;
                } else {
                    return b;
                }
            }
        }

    }


    // -------------------------------------------------- ByteEntry Inner Class


    public static class ByteEntry {

        public byte[] name = null;
        public String enc = null;
        public String value = null;

        public String toString() {
            return value;
        }
        public int hashCode() {
            return value.hashCode();
        }
        public boolean equals(Object obj) {
            if (obj instanceof ByteEntry) {
                return value.equals(((ByteEntry) obj).value);
            }
            return false;
        }
        
    }


    // -------------------------------------------------- CharEntry Inner Class


    public static class CharEntry {

        public char[] name = null;
        public String value = null;

        public String toString() {
            return value;
        }
        public int hashCode() {
            return value.hashCode();
        }
        public boolean equals(Object obj) {
            if (obj instanceof CharEntry) {
                return value.equals(((CharEntry) obj).value);
            }
            return false;
        }
        
    }


}

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