Pool Service

The Pool Service extends the functionality of the Factory Service by adding support for pooling objects intantiated from the given class name or Class object reference. Pooling of objects stabilizes memory consumption and reduces garbage collection making response times in server applications more predictable.

When a new instance is requested from the service, it first checks its pool if one is available. If the the pool is empty, a new object will be instantiated from the given class. If the class is specified by its name, the request to create an instance will be forwarded to the Factory Service.

For pooled objects implementing the Recyclable interface, a recycle method will be called, when they are taken from the pool, and a dispose method, when they are returned to the pool. Implementations of the methods should clear and initialize the pooled instances correspondingly. Objects that do not implement the interface can also be pooled, if they do not need to perform any specific actions during pooling. A RecyclableSupport class can be extended to get a minimal implementation of the interface.

An ArrayCtorRecyclable interface extends the Recyclable interface providing a more efficient recycle method with less reflection for recycling frequently used objects having constuctors with parameters.

Configuration

# -------------------------------------------------------------------
# 
#  S E R V I C E S
#
# -------------------------------------------------------------------
# Classes for Turbine Services should be defined here.
# Format: services.[name].classname=[implementing class]
#
# To specify properties of a service use the following syntax:
# service.[name].[property]=[value]

services.PoolService.classname=org.apache.turbine.services.pool.TurbinePoolService
.
.
.
# -------------------------------------------------------------------
# 
#  P O O L  S E R V I C E
#
# -------------------------------------------------------------------

# Default capacity of pools of the Object pooling service.
#
# Default: 128
services.PoolService.pool.capacity = 128

# Class specific capacities used instead of the default if specified.
#
#services.PoolService.pool.capacity.org.apache.turbine.services.rundata.DefaultTurbineRunData=512

Usage

The Pool Service can be called instead of the Factory Service, when instantiating objects that are needed repeatedly e.g. for processing client requests. Intances of RunData implementations, ParameterParser and CookieParser implementations, Pull Service tools, etc, are typical examples of pooled objects. Used objects must be returned to the Pool Service for recycling. The TurbinePool class is a static accessor for common methods of the Pool Service:

// Get a pooled DOM parser.
DocumentBuilder parser = 
    TurbinePool.getInstance("javax.xml.parsers.DocumentBuilder");
        
// Parse an XML document.
Document doc = parser.parse(myfile);

// Return the parser to the pool.
TurbinePool.putInstance(parser);