org.apache.tomcat.dbcp.pool2

## Class PoolUtils

- java.lang.Object
- - org.apache.tomcat.dbcp.pool2.PoolUtils

-     public final class PoolUtils
      extends Object

  This class consists exclusively of static methods that operate on or return ObjectPool or KeyedObjectPool related interfaces.
  Since:
    2.0

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `MSG_NULL_KEY`
    `static String` | `MSG_NULL_KEYS`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PoolUtils()` PoolUtils instances should NOT be constructed in standard programming.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static <K,V> Map<K,TimerTask>` | `checkMinIdle(KeyedObjectPool<K,V> keyedPool, Collection<K> keys, int minIdle, long period)` Periodically check the idle object count for each key in the `Collection keys` in the keyedPool.
    `static <K,V> TimerTask` | `checkMinIdle(KeyedObjectPool<K,V> keyedPool, K key, int minIdle, long period)` Periodically check the idle object count for the key in the keyedPool.
    `static <T> TimerTask` | `checkMinIdle(ObjectPool<T> pool, int minIdle, long period)` Periodically check the idle object count for the pool.
    `static void` | `checkRethrow(Throwable t)` Should the supplied Throwable be re-thrown (eg if it is an instance of one of the Throwables that should never be swallowed).
    `static <K,V> void` | `prefill(KeyedObjectPool<K,V> keyedPool, Collection<K> keys, int count)` Deprecated. Use `KeyedObjectPool.addObjects(Collection, int)`.
    `static <K,V> void` | `prefill(KeyedObjectPool<K,V> keyedPool, K key, int count)` Deprecated. Use `KeyedObjectPool.addObjects(Object, int)`.
    `static <T> void` | `prefill(ObjectPool<T> pool, int count)` Deprecated. Use `ObjectPool.addObjects(int)`.
    `static <K,V> KeyedPooledObjectFactory<K,V>` | `synchronizedKeyedPooledFactory(KeyedPooledObjectFactory<K,V> keyedFactory)` Returns a synchronized (thread-safe) KeyedPooledObjectFactory backed by the specified KeyedPoolableObjectFactory.
    `static <T> PooledObjectFactory<T>` | `synchronizedPooledFactory(PooledObjectFactory<T> factory)` Returns a synchronized (thread-safe) PooledObjectFactory backed by the specified PooledObjectFactory.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### MSG_NULL_KEY

          public static final String MSG_NULL_KEY

      See Also:
        Constant Field Values

    - #### MSG_NULL_KEYS

          public static final String MSG_NULL_KEYS

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### PoolUtils

          public PoolUtils()

      PoolUtils instances should NOT be constructed in standard programming. Instead, the class should be used procedurally: PoolUtils.adapt(aPool);. This constructor is public to permit tools that require a JavaBean instance to operate.

  - ### Method Detail

    - #### checkRethrow

          public static void checkRethrow(Throwable t)

      Should the supplied Throwable be re-thrown (eg if it is an instance of one of the Throwables that should never be swallowed). Used by the pool error handling for operations that throw exceptions that normally need to be ignored.
      Parameters:
        `t` - The Throwable to check
      Throws:
        `ThreadDeath` - if that is passed in
        `VirtualMachineError` - if that is passed in

    - #### checkMinIdle

          public static <T> TimerTask checkMinIdle(ObjectPool<T> pool,
                                   int minIdle,
                                   long period)
                                        throws IllegalArgumentException

      Periodically check the idle object count for the pool. At most one idle object will be added per period. If there is an exception when calling `ObjectPool.addObject()` then no more checks will be performed.
      Type Parameters:
        `T` - the type of objects in the pool
      Parameters:
        `pool` - the pool to check periodically.
        `minIdle` - if the `ObjectPool.getNumIdle()` is less than this then add an idle object.
        `period` - the frequency to check the number of idle objects in a pool, see `Timer.schedule(TimerTask, long, long)`.
      Returns:
        the `TimerTask` that will periodically check the pools idle object count.
      Throws:
        `IllegalArgumentException` - when `pool` is `null` or when `minIdle` is negative or when `period` isn't valid for `Timer.schedule(TimerTask, long, long)`

    - #### checkMinIdle

          public static <K,V> TimerTask checkMinIdle(KeyedObjectPool<K,V> keyedPool,
                                     K key,
                                     int minIdle,
                                     long period)
                                        throws IllegalArgumentException

      Periodically check the idle object count for the key in the keyedPool. At most one idle object will be added per period. If there is an exception when calling `KeyedObjectPool.addObject(Object)` then no more checks for that key will be performed.
      Type Parameters:
        `K` - the type of the pool key
        `V` - the type of pool entries
      Parameters:
        `keyedPool` - the keyedPool to check periodically.
        `key` - the key to check the idle count of.
        `minIdle` - if the `KeyedObjectPool.getNumIdle(Object)` is less than this then add an idle object.
        `period` - the frequency to check the number of idle objects in a keyedPool, see `Timer.schedule(TimerTask, long, long)`.
      Returns:
        the `TimerTask` that will periodically check the pools idle object count.
      Throws:
        `IllegalArgumentException` - when `keyedPool`, `key` is `null` or when `minIdle` is negative or when `period` isn't valid for `Timer.schedule(TimerTask, long, long)`.

    - #### checkMinIdle

          public static <K,V> Map<K,TimerTask> checkMinIdle(KeyedObjectPool<K,V> keyedPool,
                                            Collection<K> keys,
                                            int minIdle,
                                            long period)
                                               throws IllegalArgumentException

      Periodically check the idle object count for each key in the `Collection keys` in the keyedPool. At most one idle object will be added per period.
      Type Parameters:
        `K` - the type of the pool key
        `V` - the type of pool entries
      Parameters:
        `keyedPool` - the keyedPool to check periodically.
        `keys` - a collection of keys to check the idle object count.
        `minIdle` - if the `KeyedObjectPool.getNumIdle(Object)` is less than this then add an idle object.
        `period` - the frequency to check the number of idle objects in a keyedPool, see `Timer.schedule(TimerTask, long, long)`.
      Returns:
        a `Map` of key and `TimerTask` pairs that will periodically check the pools idle object count.
      Throws:
        `IllegalArgumentException` - when `keyedPool`, `keys`, or any of the values in the collection is `null` or when `minIdle` is negative or when `period` isn't valid for `Timer.schedule(TimerTask, long, long)`.
      See Also:
        `checkMinIdle(KeyedObjectPool, Object, int, long)`

    - #### prefill

          @Deprecated
          public static <T> void prefill(ObjectPool<T> pool,
                                    int count)
                              throws Exception,
                                     IllegalArgumentException

      Deprecated. Use `ObjectPool.addObjects(int)`.
      Calls `ObjectPool.addObject()` on `pool` `count` number of times.
      Type Parameters:
        `T` - the type of objects in the pool
      Parameters:
        `pool` - the pool to prefill.
        `count` - the number of idle objects to add.
      Throws:
        `Exception` - when `ObjectPool.addObject()` fails.
        `IllegalArgumentException` - when `pool` is `null`.

    - #### prefill

          @Deprecated
          public static <K,V> void prefill(KeyedObjectPool<K,V> keyedPool,
                                      K key,
                                      int count)
                              throws Exception,
                                     IllegalArgumentException

      Deprecated. Use `KeyedObjectPool.addObjects(Object, int)`.
      Calls `KeyedObjectPool.addObject(Object)` on `keyedPool` with `key` `count` number of times.
      Type Parameters:
        `K` - the type of the pool key
        `V` - the type of pool entries
      Parameters:
        `keyedPool` - the keyedPool to prefill.
        `key` - the key to add objects for.
        `count` - the number of idle objects to add for `key`.
      Throws:
        `Exception` - when `KeyedObjectPool.addObject(Object)` fails.
        `IllegalArgumentException` - when `keyedPool` or `key` is `null`.

    - #### prefill

          @Deprecated
          public static <K,V> void prefill(KeyedObjectPool<K,V> keyedPool,
                                      Collection<K> keys,
                                      int count)
                              throws Exception,
                                     IllegalArgumentException

      Deprecated. Use `KeyedObjectPool.addObjects(Collection, int)`.
      Calls `KeyedObjectPool.addObject(Object)` on `keyedPool` with each key in `keys` for `count` number of times. This has the same effect as calling `prefill(KeyedObjectPool, Object, int)` for each key in the `keys` collection.
      Type Parameters:
        `K` - the type of the pool key
        `V` - the type of pool entries
      Parameters:
        `keyedPool` - the keyedPool to prefill.
        `keys` - `Collection` of keys to add objects for.
        `count` - the number of idle objects to add for each `key`.
      Throws:
        `Exception` - when `KeyedObjectPool.addObject(Object)` fails.
        `IllegalArgumentException` - when `keyedPool`, `keys`, or any value in `keys` is `null`.
      See Also:
        `prefill(KeyedObjectPool, Object, int)`

    - #### synchronizedPooledFactory

          public static <T> PooledObjectFactory<T> synchronizedPooledFactory(PooledObjectFactory<T> factory)

      Returns a synchronized (thread-safe) PooledObjectFactory backed by the specified PooledObjectFactory.
      Type Parameters:
        `T` - the type of objects in the pool
      Parameters:
        `factory` - the PooledObjectFactory to be "wrapped" in a synchronized PooledObjectFactory.
      Returns:
        a synchronized view of the specified PooledObjectFactory.

    - #### synchronizedKeyedPooledFactory

          public static <K,V> KeyedPooledObjectFactory<K,V> synchronizedKeyedPooledFactory(KeyedPooledObjectFactory<K,V> keyedFactory)

      Returns a synchronized (thread-safe) KeyedPooledObjectFactory backed by the specified KeyedPoolableObjectFactory.
      Type Parameters:
        `K` - the type of the pool key
        `V` - the type of pool entries
      Parameters:
        `keyedFactory` - the KeyedPooledObjectFactory to be "wrapped" in a synchronized KeyedPooledObjectFactory.
      Returns:
        a synchronized view of the specified KeyedPooledObjectFactory.

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