genericobjectpool.java

Apache的通用池Jar包

                            ; // ignored
                        }
                    }
                }
            }
        } // if !empty
    }
    
    /**
     * Check to see if we are below our minimum number of objects
     * if so enough to bring us back to our minimum.
     */
    private void ensureMinIdle() throws Exception {
        // this method isn't synchronized so the
        // calculateDeficit is done at the beginning
        // as a loop limit and a second time inside the loop
        // to stop when another thread already returned the
        // needed objects
        int objectDeficit = calculateDeficit();
        for ( int j = 0 ; j < objectDeficit && calculateDeficit() > 0 ; j++ ) {
            addObject();
        }
    }

    private synchronized int calculateDeficit() {
        int objectDeficit = getMinIdle() - getNumIdle();
        if (_maxActive > 0) {
            int growLimit = Math.max(0, getMaxActive() - getNumActive() - getNumIdle());
            objectDeficit = Math.min(objectDeficit, growLimit);
        }
        return objectDeficit;
    } 

    /**
     * Create an object, and place it into the pool.
     * addObject() is useful for "pre-loading" a pool with idle objects.
     */
    public void addObject() throws Exception {
        Object obj = _factory.makeObject();
        addObjectToPool(obj, false);
    }
    
    //--- non-public methods ----------------------------------------

    /**
     * Start the eviction thread or service, or when
     * <i>delay</i> is non-positive, stop it
     * if it is already running.
     */
    protected synchronized void startEvictor(long delay) {
        if(null != _evictor) {
            _evictor.cancel();
            _evictor = null;
        }
        if(delay > 0) {
            _evictor = new Evictor(delay);
            Thread t = new Thread(_evictor);
            t.setDaemon(true);
            t.start();
        }
    }

    synchronized String debugInfo() {
        StringBuffer buf = new StringBuffer();
        buf.append("Active: ").append(getNumActive()).append("\n");
        buf.append("Idle: ").append(getNumIdle()).append("\n");
        buf.append("Idle Objects:\n");
        Iterator it = _pool.iterator();
        long time = System.currentTimeMillis();
        while(it.hasNext()) {
            ObjectTimestampPair pair = (ObjectTimestampPair)(it.next());
            buf.append("\t").append(pair.value).append("\t").append(time - pair.tstamp).append("\n");
        }
        return buf.toString();
    }

    private int getNumTests() {
        if(_numTestsPerEvictionRun >= 0) {
            return _numTestsPerEvictionRun;
        } else {
            return(int)(Math.ceil((double)_pool.size()/Math.abs((double)_numTestsPerEvictionRun)));
        }
    }

    //--- inner classes ----------------------------------------------

    /**
     * A simple "struct" encapsulating an object instance and a timestamp.
     */
    class ObjectTimestampPair {
        Object value;
        long tstamp;

        ObjectTimestampPair(Object val) {
            this(val,System.currentTimeMillis());
        }

        ObjectTimestampPair(Object val, long time) {
            value = val;
            tstamp = time;
        }
    }

    /**
     * The idle object evictor thread.
     * @see #setTimeBetweenEvictionRunsMillis
     */
    class Evictor implements Runnable {
        private boolean _cancelled = false;
        private long _delay = 0L;

        public Evictor(long delay) {
            _delay = delay;
        }

        void cancel() {
            _cancelled = true;
        }

        public void run() {
            while(!_cancelled) {
                try {
                    Thread.sleep(_delay);
                } catch(Exception e) {
                    // ignored
                }
                try {
                    evict();
                } catch(Exception e) {
                    // ignored
                }
                try {
                    ensureMinIdle();
                } catch(Exception e) {
                    // ignored
                }
            }
            synchronized(GenericObjectPool.this) {
                if(null != _evictionCursor) {
                    _evictionCursor.close();
                    _evictionCursor = null;
                }
            }
        }

    }

    /**
     * A simple "struct" encapsulating the
     * configuration information for a {@link GenericObjectPool}.
     * @see GenericObjectPool#GenericObjectPool(org.apache.commons.pool.PoolableObjectFactory,org.apache.commons.pool.impl.GenericObjectPool.Config)
     * @see GenericObjectPool#setConfig
     */
    public static class Config {
        public int maxIdle = GenericObjectPool.DEFAULT_MAX_IDLE;
        public int minIdle = GenericObjectPool.DEFAULT_MIN_IDLE;
        public int maxActive = GenericObjectPool.DEFAULT_MAX_ACTIVE;
        public long maxWait = GenericObjectPool.DEFAULT_MAX_WAIT;
        public byte whenExhaustedAction = GenericObjectPool.DEFAULT_WHEN_EXHAUSTED_ACTION;
        public boolean testOnBorrow = GenericObjectPool.DEFAULT_TEST_ON_BORROW;
        public boolean testOnReturn = GenericObjectPool.DEFAULT_TEST_ON_RETURN;
        public boolean testWhileIdle = GenericObjectPool.DEFAULT_TEST_WHILE_IDLE;
        public long timeBetweenEvictionRunsMillis = GenericObjectPool.DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
        public int numTestsPerEvictionRun =  GenericObjectPool.DEFAULT_NUM_TESTS_PER_EVICTION_RUN;
        public long minEvictableIdleTimeMillis = GenericObjectPool.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;
    }

    //--- private attributes ---------------------------------------

    /**
     * The cap on the number of idle instances in the pool.
     * @see #setMaxIdle
     * @see #getMaxIdle
     */
    private int _maxIdle = DEFAULT_MAX_IDLE;

    /**
    * The cap on the minimum number of idle instances in the pool.
    * @see #setMinIdle
    * @see #getMinIdle
    */
   private int _minIdle = DEFAULT_MIN_IDLE;

    /**
     * The cap on the total number of active instances from the pool.
     * @see #setMaxActive
     * @see #getMaxActive
     */
    private int _maxActive = DEFAULT_MAX_ACTIVE;

    /**
     * The maximum amount of time (in millis) the
     * {@link #borrowObject} method should block before throwing
     * an exception when the pool is exhausted and the
     * {@link #getWhenExhaustedAction "when exhausted" action} is
     * {@link #WHEN_EXHAUSTED_BLOCK}.
     *
     * When less than 0, the {@link #borrowObject} method
     * may block indefinitely.
     *
     * @see #setMaxWait
     * @see #getMaxWait
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #setWhenExhaustedAction
     * @see #getWhenExhaustedAction
     */
    private long _maxWait = DEFAULT_MAX_WAIT;

    /**
     * The action to take when the {@link #borrowObject} method
     * is invoked when the pool is exhausted (the maximum number
     * of "active" objects has been reached).
     *
     * @see #WHEN_EXHAUSTED_BLOCK
     * @see #WHEN_EXHAUSTED_FAIL
     * @see #WHEN_EXHAUSTED_GROW
     * @see #DEFAULT_WHEN_EXHAUSTED_ACTION
     * @see #setWhenExhaustedAction
     * @see #getWhenExhaustedAction
     */
    private byte _whenExhaustedAction = DEFAULT_WHEN_EXHAUSTED_ACTION;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned by the {@link #borrowObject}
     * method.  If the object fails to validate,
     * it will be dropped from the pool, and we will attempt
     * to borrow another.
     *
     * @see #setTestOnBorrow
     * @see #getTestOnBorrow
     */
    private boolean _testOnBorrow = DEFAULT_TEST_ON_BORROW;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * before being returned to the pool within the
     * {@link #returnObject}.
     *
     * @see #getTestOnReturn
     * @see #setTestOnReturn
     */
    private boolean _testOnReturn = DEFAULT_TEST_ON_RETURN;

    /**
     * When <tt>true</tt>, objects will be
     * {@link PoolableObjectFactory#validateObject validated}
     * by the idle object evictor (if any).  If an object
     * fails to validate, it will be dropped from the pool.
     *
     * @see #setTestWhileIdle
     * @see #getTestWhileIdle
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private boolean _testWhileIdle = DEFAULT_TEST_WHILE_IDLE;

    /**
     * The number of milliseconds to sleep between runs of the
     * idle object evictor thread.
     * When non-positive, no idle object evictor thread will be
     * run.
     *
     * @see #setTimeBetweenEvictionRunsMillis
     * @see #getTimeBetweenEvictionRunsMillis
     */
    private long _timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;

    /**
     * The number of objects to examine during each run of the
     * idle object evictor thread (if any).
     * <p>
     * When a negative value is supplied, <tt>ceil({@link #getNumIdle})/abs({@link #getNumTestsPerEvictionRun})</tt>
     * tests will be run.  I.e., when the value is <i>-n</i>, roughly one <i>n</i>th of the
     * idle objects will be tested per run.
     *
     * @see #setNumTestsPerEvictionRun
     * @see #getNumTestsPerEvictionRun
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private int _numTestsPerEvictionRun =  DEFAULT_NUM_TESTS_PER_EVICTION_RUN;

    /**
     * The minimum amount of time an object may sit idle in the pool
     * before it is eligable for eviction by the idle object evictor
     * (if any).
     * When non-positive, no objects will be evicted from the pool
     * due to idle time alone.
     *
     * @see #setMinEvictableIdleTimeMillis
     * @see #getMinEvictableIdleTimeMillis
     * @see #getTimeBetweenEvictionRunsMillis
     * @see #setTimeBetweenEvictionRunsMillis
     */
    private long _minEvictableIdleTimeMillis = DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;

    /** My pool. */
    private CursorableLinkedList _pool = null;

    /** My {@link PoolableObjectFactory}. */
    private PoolableObjectFactory _factory = null;

    /**
     * The number of objects {@link #borrowObject} borrowed
     * from the pool, but not yet returned.
     */
    private int _numActive = 0;

    /**
     * My idle object eviction thread, if any.
     */
    private Evictor _evictor = null;

    private CursorableLinkedList.Cursor _evictionCursor = null;
}