org.apache.commons.pool.impl
Class GenericObjectPool

java.lang.Object
  extended by org.apache.commons.pool.BaseObjectPool
      extended by org.apache.commons.pool.impl.GenericObjectPool
All Implemented Interfaces:
ObjectPool

public class GenericObjectPool
extends BaseObjectPool
implements ObjectPool

A configurable ObjectPool implementation.

When coupled with the appropriate PoolableObjectFactory, GenericObjectPool provides robust pooling functionality for arbitrary objects.

A GenericObjectPool provides a number of configurable parameters:

Optionally, one may configure the pool to examine and possibly evict objects as they sit idle in the pool and to ensure that a minimum number of idle objects are available. This is performed by an "idle object eviction" thread, which runs asynchronously. Caution should be used when configuring this optional feature. Eviction runs contend with client threads for access to objects in the pool, so if they run too frequently performance issues may result. The idle object eviction thread may be configured using the following attributes:

The pool can be configured to behave as a LIFO queue with respect to idle objects - always returning the most recently used object from the pool, or as a FIFO queue, where borrowObject always returns the oldest object in the idle object pool.

GenericObjectPool is not usable without a PoolableObjectFactory. A non-null factory must be provided either as a constructor argument or via a call to setFactory(org.apache.commons.pool.PoolableObjectFactory) before the pool is used.

Implementation note: To prevent possible deadlocks, care has been taken to ensure that no call to a factory method will occur within a synchronization block. See POOL-125 and DBCP-44 for more information.

Since:
Pool 1.0
Version:
$Revision: 892236 $ $Date: 2013-12-31 04:43:12 +0000 (Tue, 31 Dec 2013) $
Author:
Rodney Waldhoff, Dirk Verbeeck, Sandy McArthur
See Also:
GenericKeyedObjectPool

Nested Class Summary
static class GenericObjectPool.Config
          A simple "struct" encapsulating the configuration information for a GenericObjectPool.
 
Field Summary
static boolean DEFAULT_LIFO
          The default LIFO status.
static int DEFAULT_MAX_ACTIVE
          The default cap on the total number of active instances from the pool.
static int DEFAULT_MAX_IDLE
          The default cap on the number of "sleeping" instances in the pool.
static long DEFAULT_MAX_WAIT
          The default maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK.
static long DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS
          The default value for getMinEvictableIdleTimeMillis().
static int DEFAULT_MIN_IDLE
          The default minimum number of "sleeping" instances in the pool before before the evictor thread (if active) spawns new objects.
static int DEFAULT_NUM_TESTS_PER_EVICTION_RUN
          The default number of objects to examine per run in the idle object evictor.
static long DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS
          The default value for getSoftMinEvictableIdleTimeMillis().
static boolean DEFAULT_TEST_ON_BORROW
          The default "test on borrow" value.
static boolean DEFAULT_TEST_ON_RETURN
          The default "test on return" value.
static boolean DEFAULT_TEST_WHILE_IDLE
          The default "test while idle" value.
static long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS
          The default "time between eviction runs" value.
static byte DEFAULT_WHEN_EXHAUSTED_ACTION
          The default "when exhausted action" for the pool.
static byte WHEN_EXHAUSTED_BLOCK
          A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should block until a new object is available, or the maximum wait time has been reached.
static byte WHEN_EXHAUSTED_FAIL
          A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should fail, throwing a NoSuchElementException.
static byte WHEN_EXHAUSTED_GROW
          A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should simply create a new object anyway.
 
Constructor Summary
GenericObjectPool()
          Create a new GenericObjectPool with default properties.
GenericObjectPool(PoolableObjectFactory factory)
          Create a new GenericObjectPool using the specified factory.
GenericObjectPool(PoolableObjectFactory factory, GenericObjectPool.Config config)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, boolean testOnBorrow, boolean testOnReturn)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, int minIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, int minIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle, long softMinEvictableIdleTimeMillis)
          Create a new GenericObjectPool using the specified values.
GenericObjectPool(PoolableObjectFactory factory, int maxActive, byte whenExhaustedAction, long maxWait, int maxIdle, int minIdle, boolean testOnBorrow, boolean testOnReturn, long timeBetweenEvictionRunsMillis, int numTestsPerEvictionRun, long minEvictableIdleTimeMillis, boolean testWhileIdle, long softMinEvictableIdleTimeMillis, boolean lifo)
          Create a new GenericObjectPool using the specified values.
 
Method Summary
 void addObject()
          Create an object, and place it into the pool.
 Object borrowObject()
          Borrows an object from the pool.
 void clear()
          Clears any objects sitting idle in the pool by removing them from the idle instance pool and then invoking the configured PoolableObjectFactory.destroyObject(Object) method on each idle instance.
 void close()
          Closes the pool.
 void evict()
          Perform numTests idle object eviction tests, evicting examined objects that meet the criteria for eviction.
 boolean getLifo()
          Whether or not the idle object pool acts as a LIFO queue.
 int getMaxActive()
          Returns the maximum number of objects that can be allocated by the pool (checked out to clients, or idle awaiting checkout) at a given time.
 int getMaxIdle()
          Returns the cap on the number of "idle" instances in the pool.
 long getMaxWait()
          Returns the maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK.
 long getMinEvictableIdleTimeMillis()
          Returns the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any).
 int getMinIdle()
          Returns the minimum number of objects allowed in the pool before the evictor thread (if active) spawns new objects.
 int getNumActive()
          Return the number of instances currently borrowed from this pool.
 int getNumIdle()
          Return the number of instances currently idle in this pool.
 int getNumTestsPerEvictionRun()
          Returns the max number of objects to examine during each run of the idle object evictor thread (if any).
 long getSoftMinEvictableIdleTimeMillis()
          Returns the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any), with the extra condition that at least "minIdle" amount of object remain in the pool.
 boolean getTestOnBorrow()
          When true, objects will be validated before being returned by the borrowObject() method.
 boolean getTestOnReturn()
          When true, objects will be validated before being returned to the pool within the returnObject(java.lang.Object).
 boolean getTestWhileIdle()
          When true, objects will be validated by the idle object evictor (if any).
 long getTimeBetweenEvictionRunsMillis()
          Returns the number of milliseconds to sleep between runs of the idle object evictor thread.
 byte getWhenExhaustedAction()
          Returns the action to take when the borrowObject() method is invoked when the pool is exhausted (the maximum number of "active" objects has been reached).
 void invalidateObject(Object obj)
          Invalidates an object from the pool.
 void returnObject(Object obj)
          Returns an object instance to the pool.
 void setConfig(GenericObjectPool.Config conf)
          Sets my configuration.
 void setFactory(PoolableObjectFactory factory)
          Deprecated. to be removed in version 2.0
 void setLifo(boolean lifo)
          Sets the LIFO property of the pool.
 void setMaxActive(int maxActive)
          Sets the cap on the number of objects that can be allocated by the pool (checked out to clients, or idle awaiting checkout) at a given time.
 void setMaxIdle(int maxIdle)
          Sets the cap on the number of "idle" instances in the pool.
 void setMaxWait(long maxWait)
          Sets the maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK.
 void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis)
          Sets the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any).
 void setMinIdle(int minIdle)
          Sets the minimum number of objects allowed in the pool before the evictor thread (if active) spawns new objects.
 void setNumTestsPerEvictionRun(int numTestsPerEvictionRun)
          Sets the max number of objects to examine during each run of the idle object evictor thread (if any).
 void setSoftMinEvictableIdleTimeMillis(long softMinEvictableIdleTimeMillis)
          Sets the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any), with the extra condition that at least "minIdle" object instances remain in the pool.
 void setTestOnBorrow(boolean testOnBorrow)
          When true, objects will be validated before being returned by the borrowObject() method.
 void setTestOnReturn(boolean testOnReturn)
          When true, objects will be validated before being returned to the pool within the returnObject(java.lang.Object).
 void setTestWhileIdle(boolean testWhileIdle)
          When true, objects will be validated by the idle object evictor (if any).
 void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis)
          Sets the number of milliseconds to sleep between runs of the idle object evictor thread.
 void setWhenExhaustedAction(byte whenExhaustedAction)
          Sets the action to take when the borrowObject() method is invoked when the pool is exhausted (the maximum number of "active" objects has been reached).
protected  void startEvictor(long delay)
          Start the eviction thread or service, or when delay is non-positive, stop it if it is already running.
 
Methods inherited from class org.apache.commons.pool.BaseObjectPool
assertOpen, isClosed
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

WHEN_EXHAUSTED_FAIL

public static final byte WHEN_EXHAUSTED_FAIL
A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should fail, throwing a NoSuchElementException.

See Also:
WHEN_EXHAUSTED_BLOCK, WHEN_EXHAUSTED_GROW, setWhenExhaustedAction(byte), Constant Field Values

WHEN_EXHAUSTED_BLOCK

public static final byte WHEN_EXHAUSTED_BLOCK
A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should block until a new object is available, or the maximum wait time has been reached.

See Also:
WHEN_EXHAUSTED_FAIL, WHEN_EXHAUSTED_GROW, setMaxWait(long), getMaxWait(), setWhenExhaustedAction(byte), Constant Field Values

WHEN_EXHAUSTED_GROW

public static final byte WHEN_EXHAUSTED_GROW
A "when exhausted action" type indicating that when the pool is exhausted (i.e., the maximum number of active objects has been reached), the borrowObject() method should simply create a new object anyway.

See Also:
WHEN_EXHAUSTED_FAIL, WHEN_EXHAUSTED_GROW, setWhenExhaustedAction(byte), Constant Field Values

DEFAULT_MAX_IDLE

public static final int DEFAULT_MAX_IDLE
The default cap on the number of "sleeping" instances in the pool.

See Also:
getMaxIdle(), setMaxIdle(int), Constant Field Values

DEFAULT_MIN_IDLE

public static final int DEFAULT_MIN_IDLE
The default minimum number of "sleeping" instances in the pool before before the evictor thread (if active) spawns new objects.

See Also:
getMinIdle(), setMinIdle(int), Constant Field Values

DEFAULT_MAX_ACTIVE

public static final int DEFAULT_MAX_ACTIVE
The default cap on the total number of active instances from the pool.

See Also:
getMaxActive(), Constant Field Values

DEFAULT_WHEN_EXHAUSTED_ACTION

public static final byte DEFAULT_WHEN_EXHAUSTED_ACTION
The default "when exhausted action" for the pool.

See Also:
WHEN_EXHAUSTED_BLOCK, WHEN_EXHAUSTED_FAIL, WHEN_EXHAUSTED_GROW, setWhenExhaustedAction(byte), Constant Field Values

DEFAULT_LIFO

public static final boolean DEFAULT_LIFO
The default LIFO status. True means that borrowObject returns the most recently used ("last in") idle object in the pool (if there are idle instances available). False means that the pool behaves as a FIFO queue - objects are taken from the idle object pool in the order that they are returned to the pool.

Since:
1.4
See Also:
setLifo(boolean), Constant Field Values

DEFAULT_MAX_WAIT

public static final long DEFAULT_MAX_WAIT
The default maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK.

See Also:
getMaxWait(), setMaxWait(long), Constant Field Values

DEFAULT_TEST_ON_BORROW

public static final boolean DEFAULT_TEST_ON_BORROW
The default "test on borrow" value.

See Also:
getTestOnBorrow(), setTestOnBorrow(boolean), Constant Field Values

DEFAULT_TEST_ON_RETURN

public static final boolean DEFAULT_TEST_ON_RETURN
The default "test on return" value.

See Also:
getTestOnReturn(), setTestOnReturn(boolean), Constant Field Values

DEFAULT_TEST_WHILE_IDLE

public static final boolean DEFAULT_TEST_WHILE_IDLE
The default "test while idle" value.

See Also:
getTestWhileIdle(), setTestWhileIdle(boolean), getTimeBetweenEvictionRunsMillis(), setTimeBetweenEvictionRunsMillis(long), Constant Field Values

DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS

public static final long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS
The default "time between eviction runs" value.

See Also:
getTimeBetweenEvictionRunsMillis(), setTimeBetweenEvictionRunsMillis(long), Constant Field Values

DEFAULT_NUM_TESTS_PER_EVICTION_RUN

public static final int DEFAULT_NUM_TESTS_PER_EVICTION_RUN
The default number of objects to examine per run in the idle object evictor.

See Also:
getNumTestsPerEvictionRun(), setNumTestsPerEvictionRun(int), getTimeBetweenEvictionRunsMillis(), setTimeBetweenEvictionRunsMillis(long), Constant Field Values

DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS

public static final long DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS
The default value for getMinEvictableIdleTimeMillis().

See Also:
getMinEvictableIdleTimeMillis(), setMinEvictableIdleTimeMillis(long), Constant Field Values

DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS

public static final long DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS
The default value for getSoftMinEvictableIdleTimeMillis().

See Also:
getSoftMinEvictableIdleTimeMillis(), setSoftMinEvictableIdleTimeMillis(long), Constant Field Values
Constructor Detail

GenericObjectPool

public GenericObjectPool()
Create a new GenericObjectPool with default properties.


GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory)
Create a new GenericObjectPool using the specified factory.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         GenericObjectPool.Config config)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
config - a non-null GenericObjectPool.Config describing my configuration

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed from me at one time (see setMaxActive(int))

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed from me at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see getWhenExhaustedAction())
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted an and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see getMaxWait())

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         boolean testOnBorrow,
                         boolean testOnReturn)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see getWhenExhaustedAction())
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted an and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see getMaxWait())
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see getTestOnBorrow())
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see getTestOnReturn())

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see getWhenExhaustedAction())
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see getMaxWait())
maxIdle - the maximum number of idle objects in my pool (see getMaxIdle())

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle,
                         boolean testOnBorrow,
                         boolean testOnReturn)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see getWhenExhaustedAction())
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see getMaxWait())
maxIdle - the maximum number of idle objects in my pool (see getMaxIdle())
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see getTestOnBorrow())
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see getTestOnReturn())

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle,
                         boolean testOnBorrow,
                         boolean testOnReturn,
                         long timeBetweenEvictionRunsMillis,
                         int numTestsPerEvictionRun,
                         long minEvictableIdleTimeMillis,
                         boolean testWhileIdle)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see setWhenExhaustedAction(byte))
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see setMaxWait(long))
maxIdle - the maximum number of idle objects in my pool (see setMaxIdle(int))
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see setTestOnBorrow(boolean))
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see setTestOnReturn(boolean))
timeBetweenEvictionRunsMillis - the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see setTimeBetweenEvictionRunsMillis(long))
numTestsPerEvictionRun - the number of idle objects to examine per run within the idle object eviction thread (if any) (see setNumTestsPerEvictionRun(int))
minEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction (see setMinEvictableIdleTimeMillis(long))
testWhileIdle - whether or not to validate objects in the idle object eviction thread, if any (see setTestWhileIdle(boolean))

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle,
                         int minIdle,
                         boolean testOnBorrow,
                         boolean testOnReturn,
                         long timeBetweenEvictionRunsMillis,
                         int numTestsPerEvictionRun,
                         long minEvictableIdleTimeMillis,
                         boolean testWhileIdle)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see setWhenExhaustedAction(byte))
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see setMaxWait(long))
maxIdle - the maximum number of idle objects in my pool (see setMaxIdle(int))
minIdle - the minimum number of idle objects in my pool (see setMinIdle(int))
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see setTestOnBorrow(boolean))
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see setTestOnReturn(boolean))
timeBetweenEvictionRunsMillis - the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see setTimeBetweenEvictionRunsMillis(long))
numTestsPerEvictionRun - the number of idle objects to examine per run within the idle object eviction thread (if any) (see setNumTestsPerEvictionRun(int))
minEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction (see setMinEvictableIdleTimeMillis(long))
testWhileIdle - whether or not to validate objects in the idle object eviction thread, if any (see setTestWhileIdle(boolean))

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle,
                         int minIdle,
                         boolean testOnBorrow,
                         boolean testOnReturn,
                         long timeBetweenEvictionRunsMillis,
                         int numTestsPerEvictionRun,
                         long minEvictableIdleTimeMillis,
                         boolean testWhileIdle,
                         long softMinEvictableIdleTimeMillis)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see setWhenExhaustedAction(byte))
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see setMaxWait(long))
maxIdle - the maximum number of idle objects in my pool (see setMaxIdle(int))
minIdle - the minimum number of idle objects in my pool (see setMinIdle(int))
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see setTestOnBorrow(boolean))
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see setTestOnReturn(boolean))
timeBetweenEvictionRunsMillis - the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see setTimeBetweenEvictionRunsMillis(long))
numTestsPerEvictionRun - the number of idle objects to examine per run within the idle object eviction thread (if any) (see setNumTestsPerEvictionRun(int))
minEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction (see setMinEvictableIdleTimeMillis(long))
testWhileIdle - whether or not to validate objects in the idle object eviction thread, if any (see setTestWhileIdle(boolean))
softMinEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction with the extra condition that at least "minIdle" amount of object remain in the pool. (see setSoftMinEvictableIdleTimeMillis(long))
Since:
Pool 1.3

GenericObjectPool

public GenericObjectPool(PoolableObjectFactory factory,
                         int maxActive,
                         byte whenExhaustedAction,
                         long maxWait,
                         int maxIdle,
                         int minIdle,
                         boolean testOnBorrow,
                         boolean testOnReturn,
                         long timeBetweenEvictionRunsMillis,
                         int numTestsPerEvictionRun,
                         long minEvictableIdleTimeMillis,
                         boolean testWhileIdle,
                         long softMinEvictableIdleTimeMillis,
                         boolean lifo)
Create a new GenericObjectPool using the specified values.

Parameters:
factory - the (possibly null)PoolableObjectFactory to use to create, validate and destroy objects
maxActive - the maximum number of objects that can be borrowed at one time (see setMaxActive(int))
whenExhaustedAction - the action to take when the pool is exhausted (see setWhenExhaustedAction(byte))
maxWait - the maximum amount of time to wait for an idle object when the pool is exhausted and whenExhaustedAction is WHEN_EXHAUSTED_BLOCK (otherwise ignored) (see setMaxWait(long))
maxIdle - the maximum number of idle objects in my pool (see setMaxIdle(int))
minIdle - the minimum number of idle objects in my pool (see setMinIdle(int))
testOnBorrow - whether or not to validate objects before they are returned by the borrowObject() method (see setTestOnBorrow(boolean))
testOnReturn - whether or not to validate objects after they are returned to the returnObject(java.lang.Object) method (see setTestOnReturn(boolean))
timeBetweenEvictionRunsMillis - the amount of time (in milliseconds) to sleep between examining idle objects for eviction (see setTimeBetweenEvictionRunsMillis(long))
numTestsPerEvictionRun - the number of idle objects to examine per run within the idle object eviction thread (if any) (see setNumTestsPerEvictionRun(int))
minEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction (see setMinEvictableIdleTimeMillis(long))
testWhileIdle - whether or not to validate objects in the idle object eviction thread, if any (see setTestWhileIdle(boolean))
softMinEvictableIdleTimeMillis - the minimum number of milliseconds an object can sit idle in the pool before it is eligible for eviction with the extra condition that at least "minIdle" amount of object remain in the pool. (see setSoftMinEvictableIdleTimeMillis(long))
lifo - whether or not objects are returned in last-in-first-out order from the idle object pool (see setLifo(boolean))
Since:
Pool 1.4
Method Detail

getMaxActive

public int getMaxActive()
Returns the maximum number of objects that can be allocated by the pool (checked out to clients, or idle awaiting checkout) at a given time. When non-positive, there is no limit to the number of objects that can be managed by the pool at one time.

Returns:
the cap on the total number of object instances managed by the pool.
See Also:
setMaxActive(int)

setMaxActive

public void setMaxActive(int maxActive)
Sets the cap on the number of objects that can be allocated by the pool (checked out to clients, or idle awaiting checkout) at a given time. Use a negative value for no limit.

Parameters:
maxActive - The cap on the total number of object instances managed by the pool. Negative values mean that there is no limit to the number of objects allocated by the pool.
See Also:
getMaxActive()

getWhenExhaustedAction

public byte getWhenExhaustedAction()
Returns the action to take when the borrowObject() method is invoked when the pool is exhausted (the maximum number of "active" objects has been reached).

Returns:
one of WHEN_EXHAUSTED_BLOCK, WHEN_EXHAUSTED_FAIL or WHEN_EXHAUSTED_GROW
See Also:
setWhenExhaustedAction(byte)

setWhenExhaustedAction

public void setWhenExhaustedAction(byte whenExhaustedAction)
Sets the action to take when the borrowObject() method is invoked when the pool is exhausted (the maximum number of "active" objects has been reached).

Parameters:
whenExhaustedAction - the action code, which must be one of WHEN_EXHAUSTED_BLOCK, WHEN_EXHAUSTED_FAIL, or WHEN_EXHAUSTED_GROW
See Also:
getWhenExhaustedAction()

getMaxWait

public long getMaxWait()
Returns the maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK. When less than or equal to 0, the borrowObject() method may block indefinitely.

Returns:
maximum number of milliseconds to block when borrowing an object.
See Also:
setMaxWait(long), setWhenExhaustedAction(byte), WHEN_EXHAUSTED_BLOCK

setMaxWait

public void setMaxWait(long maxWait)
Sets the maximum amount of time (in milliseconds) the borrowObject() method should block before throwing an exception when the pool is exhausted and the "when exhausted" action is WHEN_EXHAUSTED_BLOCK. When less than or equal to 0, the borrowObject() method may block indefinitely.

Parameters:
maxWait - maximum number of milliseconds to block when borrowing an object.
See Also:
getMaxWait(), setWhenExhaustedAction(byte), WHEN_EXHAUSTED_BLOCK

getMaxIdle

public int getMaxIdle()
Returns the cap on the number of "idle" instances in the pool.

Returns:
the cap on the number of "idle" instances in the pool.
See Also:
setMaxIdle(int)

setMaxIdle

public void setMaxIdle(int maxIdle)
Sets the cap on the number of "idle" instances in the pool. If maxIdle is set too low on heavily loaded systems it is possible you will see objects being destroyed and almost immediately new objects being created. This is a result of the active threads momentarily returning objects faster than they are requesting them them, causing the number of idle objects to rise above maxIdle. The best value for maxIdle for heavily loaded system will vary but the default is a good starting point.

Parameters:
maxIdle - The cap on the number of "idle" instances in the pool. Use a negative value to indicate an unlimited number of idle instances.
See Also:
getMaxIdle()

setMinIdle

public void setMinIdle(int minIdle)
Sets the minimum number of objects allowed in the pool before the evictor thread (if active) spawns new objects. Note that no objects are created when numActive + numIdle >= maxActive. This setting has no effect if the idle object evictor is disabled (i.e. if timeBetweenEvictionRunsMillis <= 0).

Parameters:
minIdle - The minimum number of objects.
See Also:
getMinIdle(), getTimeBetweenEvictionRunsMillis()

getMinIdle

public int getMinIdle()
Returns the minimum number of objects allowed in the pool before the evictor thread (if active) spawns new objects. (Note no objects are created when: numActive + numIdle >= maxActive)

Returns:
The minimum number of objects.
See Also:
setMinIdle(int)

getTestOnBorrow

public boolean getTestOnBorrow()
When true, objects will be validated before being returned by the borrowObject() method. If the object fails to validate, it will be dropped from the pool, and we will attempt to borrow another.

Returns:
true if objects are validated before being borrowed.
See Also:
setTestOnBorrow(boolean)

setTestOnBorrow

public void setTestOnBorrow(boolean testOnBorrow)
When true, objects will be validated before being returned by the borrowObject() method. If the object fails to validate, it will be dropped from the pool, and we will attempt to borrow another.

Parameters:
testOnBorrow - true if objects should be validated before being borrowed.
See Also:
getTestOnBorrow()

getTestOnReturn

public boolean getTestOnReturn()
When true, objects will be validated before being returned to the pool within the returnObject(java.lang.Object).

Returns:
true when objects will be validated after returned to returnObject(java.lang.Object).
See Also:
setTestOnReturn(boolean)

setTestOnReturn

public void setTestOnReturn(boolean testOnReturn)
When true, objects will be validated before being returned to the pool within the returnObject(java.lang.Object).

Parameters:
testOnReturn - true so objects will be validated after returned to returnObject(java.lang.Object).
See Also:
getTestOnReturn()

getTimeBetweenEvictionRunsMillis

public long getTimeBetweenEvictionRunsMillis()
Returns 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.

Returns:
number of milliseconds to sleep between evictor runs.
See Also:
setTimeBetweenEvictionRunsMillis(long)

setTimeBetweenEvictionRunsMillis

public void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis)
Sets 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.

Parameters:
timeBetweenEvictionRunsMillis - number of milliseconds to sleep between evictor runs.
See Also:
getTimeBetweenEvictionRunsMillis()

getNumTestsPerEvictionRun

public int getNumTestsPerEvictionRun()
Returns the max number of objects to examine during each run of the idle object evictor thread (if any).

Returns:
max number of objects to examine during each evictor run.
See Also:
setNumTestsPerEvictionRun(int), setTimeBetweenEvictionRunsMillis(long)

setNumTestsPerEvictionRun

public void setNumTestsPerEvictionRun(int numTestsPerEvictionRun)
Sets the max number of objects to examine during each run of the idle object evictor thread (if any).

When a negative value is supplied, ceil(getNumIdle())/abs(getNumTestsPerEvictionRun()) tests will be run. That is, when the value is -n, roughly one nth of the idle objects will be tested per run. When the value is positive, the number of tests actually performed in each run will be the minimum of this value and the number of instances idle in the pool.

Parameters:
numTestsPerEvictionRun - max number of objects to examine during each evictor run.
See Also:
getNumTestsPerEvictionRun(), setTimeBetweenEvictionRunsMillis(long)

getMinEvictableIdleTimeMillis

public long getMinEvictableIdleTimeMillis()
Returns the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any).

Returns:
minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
See Also:
setMinEvictableIdleTimeMillis(long), setTimeBetweenEvictionRunsMillis(long)

setMinEvictableIdleTimeMillis

public void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis)
Sets the minimum amount of time an object may sit idle in the pool before it is eligible 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.

Parameters:
minEvictableIdleTimeMillis - minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
See Also:
getMinEvictableIdleTimeMillis(), setTimeBetweenEvictionRunsMillis(long)

getSoftMinEvictableIdleTimeMillis

public long getSoftMinEvictableIdleTimeMillis()
Returns the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any), with the extra condition that at least "minIdle" amount of object remain in the pool.

Returns:
minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
Since:
Pool 1.3
See Also:
setSoftMinEvictableIdleTimeMillis(long)

setSoftMinEvictableIdleTimeMillis

public void setSoftMinEvictableIdleTimeMillis(long softMinEvictableIdleTimeMillis)
Sets the minimum amount of time an object may sit idle in the pool before it is eligible for eviction by the idle object evictor (if any), with the extra condition that at least "minIdle" object instances remain in the pool. When non-positive, no objects will be evicted from the pool due to idle time alone.

Parameters:
softMinEvictableIdleTimeMillis - minimum amount of time an object may sit idle in the pool before it is eligible for eviction.
Since:
Pool 1.3
See Also:
getSoftMinEvictableIdleTimeMillis()

getTestWhileIdle

public boolean getTestWhileIdle()
When true, objects will be validated by the idle object evictor (if any). If an object fails to validate, it will be dropped from the pool.

Returns:
true when objects will be validated by the evictor.
See Also:
setTestWhileIdle(boolean), setTimeBetweenEvictionRunsMillis(long)

setTestWhileIdle

public void setTestWhileIdle(boolean testWhileIdle)
When true, objects will be validated by the idle object evictor (if any). If an object fails to validate, it will be dropped from the pool.

Parameters:
testWhileIdle - true so objects will be validated by the evictor.
See Also:
getTestWhileIdle(), setTimeBetweenEvictionRunsMillis(long)

getLifo

public boolean getLifo()
Whether or not the idle object pool acts as a LIFO queue. True means that borrowObject returns the most recently used ("last in") idle object in the pool (if there are idle instances available). False means that the pool behaves as a FIFO queue - objects are taken from the idle object pool in the order that they are returned to the pool.

Returns:
true if the pool is configured to act as a LIFO queue
Since:
1.4

setLifo

public void setLifo(boolean lifo)
Sets the LIFO property of the pool. True means that borrowObject returns the most recently used ("last in") idle object in the pool (if there are idle instances available). False means that the pool behaves as a FIFO queue - objects are taken from the idle object pool in the order that they are returned to the pool.

Parameters:
lifo - the new value for the LIFO property
Since:
1.4

setConfig

public void setConfig(GenericObjectPool.Config conf)
Sets my configuration.

Parameters:
conf - configuration to use.
See Also:
GenericObjectPool.Config

borrowObject

public Object borrowObject()
                    throws Exception

Borrows an object from the pool.

If there is an idle instance available in the pool, then either the most-recently returned (if lifo == true) or "oldest" (lifo == false) instance sitting idle in the pool will be activated and returned. If activation fails, or testOnBorrow is set to true and validation fails, the instance is destroyed and the next available instance is examined. This continues until either a valid instance is returned or there are no more idle instances available.

If there are no idle instances available in the pool, behavior depends on the maxActive and (if applicable) whenExhaustedAction and maxWait properties. If the number of instances checked out from the pool is less than maxActive, a new instance is created, activated and (if applicable) validated and returned to the caller.

If the pool is exhausted (no available idle instances and no capacity to create new ones), this method will either block (WHEN_EXHAUSTED_BLOCK), throw a NoSuchElementException (WHEN_EXHAUSTED_FAIL), or grow (WHEN_EXHAUSTED_GROW - ignoring maxActive). The length of time that this method will block when whenExhaustedAction == WHEN_EXHAUSTED_BLOCK is determined by the maxWait property.

When the pool is exhausted, multiple calling threads may be simultaneously blocked waiting for instances to become available. As of pool 1.5, a "fairness" algorithm has been implemented to ensure that threads receive available instances in request arrival order.

Specified by:
borrowObject in interface ObjectPool
Specified by:
borrowObject in class BaseObjectPool
Returns:
object instance
Throws:
NoSuchElementException - if an instance cannot be returned
Exception - if an instance cannot be obtained from the pool

invalidateObject

public void invalidateObject(Object obj)
                      throws Exception

Invalidates an object from the pool.

By contract, obj must have been obtained using borrowObject.

This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid.

Activation of this method decrements the active count and attempts to destroy the instance.

Specified by:
invalidateObject in interface ObjectPool
Specified by:
invalidateObject in class BaseObjectPool
Parameters:
obj - a borrowed instance to be disposed.
Throws:
Exception - if the configured PoolableObjectFactory throws an exception destroying obj

clear

public void clear()
Clears any objects sitting idle in the pool by removing them from the idle instance pool and then invoking the configured PoolableObjectFactory.destroyObject(Object) method on each idle instance.

Implementation notes:

  • This method does not destroy or effect in any way instances that are checked out of the pool when it is invoked.
  • Invoking this method does not prevent objects being returned to the idle instance pool, even during its execution. It locks the pool only during instance removal. Additional instances may be returned while removed items are being destroyed.
  • Exceptions encountered destroying idle instances are swallowed.

Specified by:
clear in interface ObjectPool
Overrides:
clear in class BaseObjectPool

getNumActive

public int getNumActive()
Return the number of instances currently borrowed from this pool.

Specified by:
getNumActive in interface ObjectPool
Overrides:
getNumActive in class BaseObjectPool
Returns:
the number of instances currently borrowed from this pool

getNumIdle

public int getNumIdle()
Return the number of instances currently idle in this pool.

Specified by:
getNumIdle in interface ObjectPool
Overrides:
getNumIdle in class BaseObjectPool
Returns:
the number of instances currently idle in this pool

returnObject

public void returnObject(Object obj)
                  throws Exception

Returns an object instance to the pool.

If maxIdle is set to a positive value and the number of idle instances has reached this value, the returning instance is destroyed.

If testOnReturn == true, the returning instance is validated before being returned to the idle instance pool. In this case, if validation fails, the instance is destroyed.

Note: There is no guard to prevent an object being returned to the pool multiple times. Clients are expected to discard references to returned objects and ensure that an object is not returned to the pool multiple times in sequence (i.e., without being borrowed again between returns). Violating this contract will result in the same object appearing multiple times in the pool and pool counters (numActive, numIdle) returning incorrect values.

Specified by:
returnObject in interface ObjectPool
Specified by:
returnObject in class BaseObjectPool
Parameters:
obj - instance to return to the pool
Throws:
Exception

close

public void close()
           throws Exception

Closes the pool. Once the pool is closed, borrowObject() will fail with IllegalStateException, but returnObject(Object) and invalidateObject(Object) will continue to work, with returned objects destroyed on return.

Destroys idle instances in the pool by invoking clear().

Specified by:
close in interface ObjectPool
Overrides:
close in class BaseObjectPool
Throws:
Exception

setFactory

public void setFactory(PoolableObjectFactory factory)
                throws IllegalStateException
Deprecated. to be removed in version 2.0

Sets the factory this pool uses to create new instances. Trying to change the factory while there are borrowed objects will throw an IllegalStateException. If there are instances idle in the pool when this method is invoked, these will be destroyed using the original factory.

Specified by:
setFactory in interface ObjectPool
Overrides:
setFactory in class BaseObjectPool
Parameters:
factory - the PoolableObjectFactory used to create new instances.
Throws:
IllegalStateException - when the factory cannot be set at this time

evict

public void evict()
           throws Exception

Perform numTests idle object eviction tests, evicting examined objects that meet the criteria for eviction. If testWhileIdle is true, examined objects are validated when visited (and removed if invalid); otherwise only objects that have been idle for more than minEvicableIdletimeMillis are removed.

Successive activations of this method examine objects in in sequence, cycling through objects in oldest-to-youngest order.

Throws:
Exception - if the pool is closed or eviction fails.

addObject

public void addObject()
               throws Exception
Create an object, and place it into the pool. addObject() is useful for "pre-loading" a pool with idle objects.

Specified by:
addObject in interface ObjectPool
Overrides:
addObject in class BaseObjectPool
Throws:
Exception - when PoolableObjectFactory.makeObject() fails.
IllegalStateException - after ObjectPool.close() has been called on this pool.
UnsupportedOperationException - when this pool cannot add new idle objects.

startEvictor

protected void startEvictor(long delay)
Start the eviction thread or service, or when delay is non-positive, stop it if it is already running.

Parameters:
delay - milliseconds between evictor runs.


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