Package org.apache.tomcat.dbcp.pool2

Interface PooledObjectFactory<T>

Type Parameters:
T - Type of element managed in this factory.
All Known Implementing Classes:
BasePooledObjectFactory, PoolableConnectionFactory
public interface PooledObjectFactory<T>
An interface defining life-cycle methods for instances to be served by an ObjectPool.

By contract, when an ObjectPool delegates to a PooledObjectFactory,

  1. makeObject() is called whenever a new instance is needed.
  2. activateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) is invoked on every instance that has been passivated before it is borrowed from the pool.
  3. validateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) may be invoked on activated instances to make sure they can be borrowed from the pool. validateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) may also be used to test an instance being returned to the pool before it is passivated. It will only be invoked on an activated instance.
  4. passivateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) is invoked on every instance when it is returned to the pool.
  5. destroyObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>) is invoked on every instance when it is being "dropped" from the pool (whether due to the response from validateObject(org.apache.tomcat.dbcp.pool2.PooledObject<T>), or for reasons specific to the pool implementation.) There is no guarantee that the instance being destroyed will be considered active, passive or in a generally consistent state.
PooledObjectFactory must be thread-safe. The only promise an ObjectPool makes is that the same instance of an object will not be passed to more than one method of a PoolableObjectFactory at a time.

While clients of a KeyedObjectPool borrow and return instances of the underlying value type V, the factory methods act on instances of PooledObject<V>. These are the object wrappers that pools use to track and maintain state information about the objects that they manage.

Since:
2.0
See Also:

  • Method Details

    • makeObject

      PooledObject<T> makeObject() throws Exception
      Creates an instance that can be served by the pool and wrap it in a PooledObject to be managed by the pool.
      Returns:
      a PooledObject wrapping an instance that can be served by the pool
      Throws:
      Exception - if there is a problem creating a new instance, this will be propagated to the code requesting an object.

    • destroyObject

      void destroyObject(PooledObject<T> p) throws Exception
      Destroys an instance no longer needed by the pool, using the default (NORMAL) DestroyMode.

      It is important for implementations of this method to be aware that there is no guarantee about what state obj will be in and the implementation should be prepared to handle unexpected errors.

      Also, an implementation must take in to consideration that instances lost to the garbage collector may never be destroyed.

      Parameters:
      p - a PooledObject wrapping the instance to be destroyed
      Throws:
      Exception - should be avoided as it may be swallowed by the pool implementation.
      See Also:

    • destroyObject

      void destroyObject(PooledObject<T> p, DestroyMode mode) throws Exception
      Destroys an instance no longer needed by the pool, using the provided DestroyMode.
      Parameters:
      p - a PooledObject wrapping the instance to be destroyed
      mode - DestroyMode providing context to the factory
      Throws:
      Exception - should be avoided as it may be swallowed by the pool implementation.
      Since:
      2.9.0
      See Also:

    • validateObject

      boolean validateObject(PooledObject<T> p)
      Ensures that the instance is safe to be returned by the pool.
      Parameters:
      p - a PooledObject wrapping the instance to be validated
      Returns:
      false if obj is not valid and should be dropped from the pool, true otherwise.

    • activateObject

      void activateObject(PooledObject<T> p) throws Exception
      Reinitializes an instance to be returned by the pool.
      Parameters:
      p - a PooledObject wrapping the instance to be activated
      Throws:
      Exception - if there is a problem activating obj, this exception may be swallowed by the pool.
      See Also:

    • passivateObject

      void passivateObject(PooledObject<T> p) throws Exception
      Uninitializes an instance to be returned to the idle object pool.
      Parameters:
      p - a PooledObject wrapping the instance to be passivated
      Throws:
      Exception - if there is a problem passivating obj, this exception may be swallowed by the pool.
      See Also: