The user is expected to have technical knowledge in the
following area,
JDBC
Technical Overview
This sample illustrates the usage of Connection caching features
in Oracle Database 10g JDBC drivers. This sample uses
the JDBC thin driver; the code remains the same for JDBC OCI, except for the
database URL syntax.
Connection caching, generally implemented in a middle tier,
is a means of keeping and using caches of physical database connections. Oracle's
implementation of Connection Caching uses the Connection Pooling Framework in
much of its operations.
Each connection cache is represented by an instance of a connection cache class
and has an associated group of pooled connection instances. For a single connection
cache instance, the associated pooled connection instances must all represent
physical connections to the same database and schema.
Pooled connection instances are created as needed, which is whenever a connection
is requested and the connection cache does not have any free pooled connection
instances.
The connection caching architecture has been redesigned so that caching is transparently
integrated into the datasource architecture. It uses the implicit connection caching
mechanism, which is more powerful and easier to use.
With the addition of new class, OracleConnectionCacheManager, applications can
use its rich set of administrative APIs to manage the connection cache. This class
replaces the deprecated OracleConnectionCacheImpl. Applications can manage their
cache either through the single OracleConnectionCacheManager instance or through
the OracleDataSource associated with the cache. The benefits of using OracleConnectionCacheManager
over OracleConnectionCacheImpl are,
Transparent access to the connection
cache
Compliance to JDBC 3.0 standards
Supports connection recycling and
refresh of stale connections
Supports attribute based search
for conceits
Supports multiple cache enabled
DataSource
Supports connection cache call back mechanism
Application Overview
Consider that a fictitious organization has internet enabled
all its applications. Sales and marketing employees of this organization use
web-based Order Entry application to monitor various Orders and order status
for various products .
This simplified Order Entry application connects to the database and fetches
the product catalog and all the products are shown to the user. User can choose
a particular product and view orders for the product. Also the application is
provided with a user interface to manage the connection cache proprties and
behaviour.
Assuming that the organization is huge, it is likely that lot of sales employees
use the Order Entry Application at the same time. As this Order Entry application
fetches the data from the database, the cost of using a dedicated physical database
connection per user is quite high. To reduce this overhead, this application
makes use of Connection Cache. This Sample shows how to set up a implicit Connection
Cache, get a Connection from the cache and return the connection to the cache
and re initialize the connection properties using the OracleConnectionCacheManager.
In this sample, the connections are closed only when the active size reaches
the maximum cache limit. This ensures that atleast one connection is available
in the cache, after it reaches the maximum limit. Also this demonstrates the
growth of the cache till the maximum set limit.
Setting up and Running
the Application
For setting up and running the application, download the ConnCacheSample.jar
and refer to the installation document.
Sample Application
Files
This section will provide a tabular listing of the sample
application files, along with their respective directory locations and a description
of what they do in the overall scheme of the application.
Directory
File
Description
ConnCacheSample/doc
Readme.html
This file
ConnCacheSample/doc
Install.html
Sample installation document
ConnCacheSample/web
EnvSetup.html
Environment variable set up readme file
ConnCacheSample/src
Java source files
Java source files used in the sample application
ConnCacheSample/web
JSP files
Used as the web interface
ConnCacheSample/config
Connection.properties
This file has the details of the database
connection parameters
ConnCacheSample/config
application.xml
This file is used to define the J2EE EAR
file, which contains the location of EJB JAR file, Web application WAR file
and is included in the EAR file
ConnCacheSample/web/WEB-INF
web.xml
This file is used to define the Web deployment
descriptors and is included in the WAR file
ConnCacheSample/web/WEB-INF
orion-web.xml
This file is used to define the container
specific deployment descriptors and is included in the WAR file. This configures
the web application classloader to override its default behaviour and direct
it to load local classes in preference to classes from a higher level.
ConnCacheSample
build.xml
Ant
build file used to build and deploy to the application
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