KeyedObjectPool (Apache Tomcat 7.0.109 API Documentation)

Type Parameters:
K - the type of keys in this pool
V - the type of objects held in this pool

All Known Implementing Classes:

BaseKeyedObjectPool, GenericKeyedObjectPool, StackKeyedObjectPool
```
public interface KeyedObjectPool<K,V>
```
A "keyed" pooling interface.
A keyed pool pools instances of multiple types. Each type may be accessed using an arbitrary key.

Example of use:
```
 Object obj = null;
 Object key = "Key";

 try {
     obj = pool.borrowObject(key);
     //...use the object...
 } catch(Exception e) {
     // invalidate the object
     pool.invalidateObject(key, obj);
     // do not return the object to the pool twice
     obj = null;
 } finally {
     // make sure the object is returned to the pool
     if(null != obj) {
         pool.returnObject(key, obj);
     }
 }
```
KeyedObjectPool implementations may choose to store at most one instance per key value, or may choose to maintain a pool of instances for each key (essentially creating a Map of pools).

See BaseKeyedObjectPool for a simple base implementation.
Since:

Pool 1.0

Author:

Rodney Waldhoff, Sandy McArthur

See Also:
KeyedPoolableObjectFactory, KeyedObjectPoolFactory, ObjectPool, BaseKeyedObjectPool

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`addObject(K key)` Create an object using the `factory` or other implementation dependent mechanism, passivate it, and then place it in the idle object pool.
`V`	`borrowObject(K key)` Obtains an instance from this pool for the specified `key`.
`void`	`clear()` Clears the pool, removing all pooled instances (optional operation).
`void`	`clear(K key)` Clears the specified pool, removing all pooled instances corresponding to the given `key` (optional operation).
`void`	`close()` Close this pool, and free any resources associated with it.
`int`	`getNumActive()` Returns the total number of instances current borrowed from this pool but not yet returned (optional operation).
`int`	`getNumActive(K key)` Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given `key` (optional operation).
`int`	`getNumIdle()` Returns the total number of instances currently idle in this pool (optional operation).
`int`	`getNumIdle(K key)` Returns the number of instances corresponding to the given `key` currently idle in this pool (optional operation).
`void`	`invalidateObject(K key, V obj)` Invalidates an object from the pool.
`void`	`returnObject(K key, V obj)` Return an instance to the pool.
`void`	`setFactory(KeyedPoolableObjectFactory<K,V> factory)` Deprecated. to be removed in pool 2.0

- Method Detail
  - borrowObject
```
V borrowObject(K key)
               throws Exception,
                      NoSuchElementException,
                      IllegalStateException
```
    Obtains an instance from this pool for the specified key.
    Instances returned from this method will have been either newly created with makeObject or will be a previously idle object and have been activated with activateObject and then validated with validateObject.
    By contract, clients must return the borrowed object using returnObject, invalidateObject, or a related method as defined in an implementation or sub-interface, using a key that is equivalent to the one used to borrow the instance in the first place.
    The behaviour of this method when the pool has been exhausted is not strictly specified (although it may be specified by implementations). Older versions of this method would return null to indicate exhaustion, newer versions are encouraged to throw a NoSuchElementException.
    
    Parameters:
    key - the key used to obtain the object
    
    Returns:
    an instance from this pool.
    
    Throws:
    
    IllegalStateException - after close has been called on this pool
    
    Exception - when makeObject throws an exception
    
    NoSuchElementException - when the pool is exhausted and cannot or will not return another instance
  - returnObject
```
void returnObject(K key,
                V obj)
                  throws Exception
```
    Return an instance to the pool. By contract, obj must have been obtained using borrowObject or a related method as defined in an implementation or sub-interface using a key that is equivalent to the one used to borrow the instance in the first place.
    
    Parameters:
    key - the key used to obtain the object
    obj - a borrowed instance to be returned.
    
    Throws:
    
    Exception
  - invalidateObject
```
void invalidateObject(K key,
                    V obj)
                      throws Exception
```
    Invalidates an object from the pool.
    
    By contract, obj must have been obtained using borrowObject or a related method as defined in an implementation or sub-interface using a key that is equivalent to the one used to borrow the Object in the first place.
    
    This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid.
    
    Parameters:
    key - the key used to obtain the object
    obj - a borrowed instance to be returned.
    
    Throws:
    
    Exception
  - addObject
```
void addObject(K key)
               throws Exception,
                      IllegalStateException,
                      UnsupportedOperationException
```
    Create an object using the factory or other implementation dependent mechanism, passivate it, and then place it in the idle object pool. addObject is useful for "pre-loading" a pool with idle objects (Optional operation).
    
    Parameters:
    key - the key a new instance should be added to
    
    Throws:
    
    Exception - when KeyedPoolableObjectFactory.makeObject(K) fails.
    
    IllegalStateException - after close() has been called on this pool.
    
    UnsupportedOperationException - when this pool cannot add new idle objects.
  - getNumIdle
```
int getNumIdle(K key)
               throws UnsupportedOperationException
```
    Returns the number of instances corresponding to the given key currently idle in this pool (optional operation). Returns a negative value if this information is not available.
    
    Parameters:
    key - the key to query
    
    Returns:
    the number of instances corresponding to the given key currently idle in this pool or a negative value if unsupported
    
    Throws:
    
    UnsupportedOperationException - deprecated: when this implementation doesn't support the operation
  - getNumActive
```
int getNumActive(K key)
                 throws UnsupportedOperationException
```
    Returns the number of instances currently borrowed from but not yet returned to the pool corresponding to the given key (optional operation). Returns a negative value if this information is not available.
    
    Parameters:
    key - the key to query
    
    Returns:
    the number of instances corresponding to the given key currently borrowed in this pool or a negative value if unsupported
    
    Throws:
    
    UnsupportedOperationException - deprecated: when this implementation doesn't support the operation
  - getNumIdle
```
int getNumIdle()
               throws UnsupportedOperationException
```
    Returns the total number of instances currently idle in this pool (optional operation). Returns a negative value if this information is not available.
    
    Returns:
    the total number of instances currently idle in this pool or a negative value if unsupported
    
    Throws:
    
    UnsupportedOperationException - deprecated: when this implementation doesn't support the operation
  - getNumActive
```
int getNumActive()
                 throws UnsupportedOperationException
```
    Returns the total number of instances current borrowed from this pool but not yet returned (optional operation). Returns a negative value if this information is not available.
    
    Returns:
    the total number of instances currently borrowed from this pool or a negative value if unsupported
    
    Throws:
    
    UnsupportedOperationException - deprecated: when this implementation doesn't support the operation
  - clear
```
void clear()
           throws Exception,
                  UnsupportedOperationException
```
    Clears the pool, removing all pooled instances (optional operation). Throws UnsupportedOperationException if the pool cannot be cleared.
    
    Throws:
    
    UnsupportedOperationException - when this implementation doesn't support the operation
    
    Exception
  - clear
```
void clear(K key)
           throws Exception,
                  UnsupportedOperationException
```
    Clears the specified pool, removing all pooled instances corresponding to the given key (optional operation). Throws UnsupportedOperationException if the pool cannot be cleared.
    
    Parameters:
    key - the key to clear
    
    Throws:
    
    UnsupportedOperationException - when this implementation doesn't support the operation
    
    Exception
  - close
```
void close()
           throws Exception
```
    Close this pool, and free any resources associated with it.
    Calling addObject or borrowObject after invoking this method on a pool will cause them to throw an IllegalStateException.
    
    Throws:
    
    Exception
  - setFactory
```
@Deprecated
void setFactory(KeyedPoolableObjectFactory<K,V> factory)
                throws IllegalStateException,
                       UnsupportedOperationException
```
    Deprecated. to be removed in pool 2.0
    
    Sets the factory the pool uses to create new instances (optional operation). Trying to change the factory after a pool has been used will frequently throw an UnsupportedOperationException. It is up to the pool implementation to determine when it is acceptable to call this method.
    
    Parameters:
    factory - the KeyedPoolableObjectFactory used to create new instances.
    
    Throws:
    
    IllegalStateException - when the factory cannot be set at this time
    
    UnsupportedOperationException - when this implementation doesn't support the operation

Interface KeyedObjectPool<K,V>

Method Summary

Method Detail

borrowObject

returnObject

invalidateObject

addObject

getNumIdle

getNumActive

getNumIdle

getNumActive

clear

clear

close

setFactory