Interface ObjectPool<T>
- Type Parameters:
- T- Type of element pooled in this pool.
- All Superinterfaces:
- AutoCloseable,- Closeable
- All Known Implementing Classes:
- BaseObjectPool,- GenericObjectPool,- SoftReferenceObjectPool
Example of use:
Object obj =null;try{ obj = pool.borrowObject();try{//...use the object...}catch(Exception e) {// invalidate the objectpool.invalidateObject(obj);// do not return the object to the pool twiceobj =null; }finally{// make sure the object is returned to the poolif(null!= obj) { pool.returnObject(obj); } } }catch(Exception e) {// failed to borrow an object}
 See BaseObjectPool for a simple base implementation.
 
- Since:
- 2.0
- See Also:
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Method SummaryModifier and TypeMethodDescriptionvoidCreates an object using thefactoryor other implementation dependent mechanism, passivate it, and then place it in the idle object pool.default voidaddObjects(int count) CallsaddObject()countnumber of times.Borrows an instance from this pool.voidclear()Clears any objects sitting idle in the pool, releasing any associated resources (optional operation).voidclose()Closes this pool, and free any resources associated with it.intGets the number of instances currently borrowed from this pool.intGets the number of instances currently idle in this pool.voidinvalidateObject(T obj) Invalidates an object from the pool.default voidinvalidateObject(T obj, DestroyMode destroyMode) Invalidates an object from the pool, using the providedDestroyModevoidreturnObject(T obj) Returns an instance to the pool.
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Method Details- 
addObjectCreates an object using thefactoryor other implementation dependent mechanism, passivate it, and then place it in the idle object pool.addObjectis useful for "pre-loading" a pool with idle objects. (Optional operation).- Throws:
- Exception- when- PooledObjectFactory.makeObject()fails.
- IllegalStateException- after- close()has been called on this pool.
- UnsupportedOperationException- when this pool cannot add new idle objects.
 
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addObjectsCallsaddObject()countnumber of times.- Parameters:
- count- the number of idle objects to add.
- Throws:
- Exception- See- addObject().
- Since:
- 2.8.0
 
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borrowObjectBorrows an instance from this pool.Instances returned from this method will have been either newly created with PooledObjectFactory.makeObject()or will be a previously idle object and have been activated withPooledObjectFactory.activateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>)and then validated withPooledObjectFactory.validateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>).By contract, clients must return the borrowed instance using returnObject(T),invalidateObject(T), or a related method as defined in an implementation or sub-interface.The behavior of this method when the pool has been exhausted is not strictly specified (although it may be specified by implementations). - Returns:
- an instance from this pool.
- Throws:
- IllegalStateException- after- closehas been called on this pool.
- Exception- when- PooledObjectFactory.makeObject()throws an exception.
- NoSuchElementException- when the pool is exhausted and cannot or will not return another instance.
 
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clearClears any objects sitting idle in the pool, releasing any associated resources (optional operation). Idle objects cleared must bePooledObjectFactory.destroyObject(PooledObject).- Throws:
- UnsupportedOperationException- if this implementation does not support the operation
- Exception- if the pool cannot be cleared
 
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closevoid close()Closes this pool, and free any resources associated with it.Calling addObject()orborrowObject()after invoking this method on a pool will cause them to throw anIllegalStateException.Implementations should silently fail if not all resources can be freed. - Specified by:
- closein interface- AutoCloseable
- Specified by:
- closein interface- Closeable
 
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getNumActiveint getNumActive()Gets the number of instances currently borrowed from this pool. Returns a negative value if this information is not available.- Returns:
- the number of instances currently borrowed from this pool.
 
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getNumIdleint getNumIdle()Gets the number of instances currently idle in this pool. This may be considered an approximation of the number of objects that can beborrowedwithout creating any new instances. Returns a negative value if this information is not available.- Returns:
- the number of instances currently idle in this pool.
 
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invalidateObjectInvalidates an object from the pool.By contract, objmust have been obtained usingborrowObject()or a related method as defined in an implementation or sub-interface.This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid. 
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invalidateObjectInvalidates an object from the pool, using the providedDestroyModeBy contract, objmust have been obtained usingborrowObject()or a related method as defined in an implementation or sub-interface.This method should be used when an object that has been borrowed is determined (due to an exception or other problem) to be invalid. 
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returnObjectReturns an instance to the pool. By contract,objmust have been obtained usingborrowObject()or a related method as defined in an implementation or sub-interface.- Parameters:
- obj- a- borrowedinstance to be returned.
- Throws:
- IllegalStateException- if an attempt is made to return an object to the pool that is in any state other than allocated (i.e. borrowed). Attempting to return an object more than once or attempting to return an object that was never borrowed from the pool will trigger this exception.
- Exception- if an instance cannot be returned to the pool
 
 
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