web server - Borland Technical Publications

System Contracts
Connection Management
Connections to an EIS are expensive resources to create and destroy. To support
scalable applications, the application server needs to be able to pool connections to
the underlying EISs. To simplify application component development, this connection
pooling mechanism needs to be transparent to the components accessing the
underlying EISs.
The Connectors specification supports connection pooling and management,
optimizing application component performance and scalability. The connection
management contract, defined between the application server and the Resource
Adapter, provides:
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A consistent application development model for connection acquisition for both
managed (n-tier) and non-managed (two-tier) applications.
A framework for the Resource Adapter to provide a standard connection factory and
connection interface based on the Common Client Interface (CCI), opaque to the
implementation for the underlying EIS.
A generic mechanism for providing different quality of services (QoS) advanced
connection pooling, transaction management, security management, error tracing
and logging - for a configured set of Resource Adapters.
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Support for the application server to implement its connection pooling facility.
VisiConnect uses connection management to:
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Create new connections to an EIS
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Configure connection factories in the Java Naming and Directory Interface (JNDI)
namespace.
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Find the right connection to an EIS from an existing set of pooled connections, and
reuse that connection.
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Hook in Borland Enterprise Server's transaction and security services.
The Borland Enterprise Server establishes, configures, caches and reuses
connections to the EIS automatically through VisiConnect.
The application component performs a lookup of a Resource Adapter connection
factory in the JNDI namespace, using the connection factory to get a connection to the
underlying EIS. The connection factory delegates the connection creation request to
the VisiConnect connection manager instance. On receiving this request, the
connection manager performs a lookup in the connection pool. If there is no connection
in the pool that can satisfy the connection request, VisiConnect uses the
ManagedConnectionFactory implemented by the Resource Adapter to create a new
physical connection to the underlying EIS. If VisiConnect finds a matching connection
in the pool, it then uses the matching ManagedConnection instance to satisfy the
connection request. If a new ManagedConnection instance is created, the server adds the
new ManagedConnection instance to the connection pool.
VisiConnect registers a ConnectionEventListener with the ManagedConnection instance.
This listener enables VisiConnect to receive event notifications related to the state of
the ManagedConnection instance. VisiConnect uses these notifications to manage
connection pooling, transactions, connection cleanup and handle error conditions.
VisiConnect uses the ManagedConnection instance to provide a Connection instance that
acts as an application-level handle to the underlying physical connection, to the
application component. The component in turn uses this handle - and not the
underlying physical connection directly - to access EIS resources.
248 BES Developer’s Guide