At the end of this chapter you will be able to:

• Describe the high-level architecture of JDBC
• List the four-driver types, and those provide by WLS
• Describe and configure Data Sources
• Use the Administration Console to manage JDBC resources

Overview of JDBC

What Is JDBC?

• JDBC is an API for uniformly accessing databases.

• JDBC provides:

  • Platform independent access to databases
  • Location transparency
  • Transparency to proprietary database issues
  • Support for both two-tier and multi-tier models for database access

JDBC Architecture

JDBC Drivers:

Type 1 Driver

• The Type 1 driver:

  • Is a JDBC-ODBC bridge
  • Usually, runs on Windows
  • Requires ODBC driver to be installed on the client machine

Type 2 Drivers

• The Type 2 driver:

  • Requires a native driver to be already installed on the client machine
  • The driver converts JDBC calls to native API calls of the database.

Type 3 Drivers

• A network server can apply several techniques to boost performance:

  • Connection Pooling
  • Load management

Type 4 Drivers

• Type 4 drivers are ‘all-Java’ driver implementations that do not require client-side configuration.

Two-Tier Architecture

• In the two-tier model, a Java application communicates directly with the DBMS.
• A JDBC driver is needed that can communicate directly with the DBMS.
• This is a client/server configuration.

Multi-Tier Architecture

• In the multi-tier model, commands are sent to a "middle tier" of services, which then sends the commands to the DBMS.
• The DBMS processes the commands and sends the results back to the middle tier, which then sends them to the client.

Choosing the Correct Driver

• Choosing the correct driver can have a significant impact on performance.
• For two-tier applications use the type 1, 2, or 4 drivers specific to the DBMS you are using.
• For multi-tier applications use:

  • Data Source lookup in a client class
  • A type 1, 2, or 4 drivers on the server, specific to the DBMS you are using
  • XA driver where transaction support is required

Data Sources:

What Is a Data Source?

• A Data Source object provides a way for a JDBC client to obtain a database connection from a connection pool.
• A Data Source:

  • Is stored in the WLS JNDI tree
  • Can support transactions
  • Is associated with a connection pool

What Is a Connection Pool?

• A connection pool is a group of ready-to-use database connections associated with a Data Source.
• Connection pools:

  • Are created at WebLogic Server startup
  • Can be administered using the Administration Console
  • Can be dynamically resized to accommodate the increasing load

Benefits of Data Sources and Connection Pools

• Some advantages of this approach are:

  • Time and overhead are saved by using an existing database connection
  • Connection information is managed in one location in the Administration Console
  • The number of connections to a database can be controlled
  • The DBMS can be changed without the application developer having to modify the underlying code

• A connection pool allows an application to “borrow” a DBMS connection.

JDBC Data Source Architecture

Modular Configuration and Deployment of JDBC Resources

• JDBC configurations in WLS are stored in XML documents:

  • All JDBC configurations must conform to the new WebLogic-jdbc.xsd schema.
  • IDEs and other tools can validate JDBC modules based on the schema.

• You create and manage JDBC resources either as system modules or as application modules.
• JDBC application modules are a WLS-specific extension of J2EE modules and can be deployed either within a J2EE application or as stand-alone modules.

How Data Sources Are Used

• A client retrieves a Data Source through JNDI lookup and uses it to obtain a database connection.

Creating a JDBC Data Source…

Creating a Data Source: Properties

Creating a Data Source: XA Options

Creating a Data Source: ConnectionProperties

Creating a Data Source: Test Database Connections & Select Targets:

Configuring a Connection Pool…

Connection Pool Checklist

• You can modify a connection pool after the Data Source has been created
• Before modifying a connection pool, you should understand:

  • The JDBC URL of the database
  • The connection properties used to authenticate a user or optionally configure the driver

• Ask your DBA for:

  • The maximum number of connections your application will be allowed.

JDBC URLs

• Database locations are specified using a JDBC Uniform Resource Locator (URL).

Examples:

Multi Data Sources…

• Multi Data Source:

  • It is an abstraction around a group of data sources
  • Determines which data source to use to satisfy the request depending on the algorithm selected in the multi-data source configuration:

    • Load balancing Or • Failover

  • Are bound to the JNDI tree

• XA Support for Multi Data Sources

  • The WLS JDBC supports using Multi Data Sources in XA transactions.
  • You can configure the data sources contained within the Multi Data Source to use XA JDBC drivers.

Monitoring & Testing Data Sources

Monitoring Data Sources: Statistics

• The Administration console provides two types of data source monitoring: statistics and testing.

Monitoring Data Sources: Testing

• The Administration console provides a mechanism for manually testing individual data sources.

Summary: 

In this chapter we discussed:

• JDBC high-level architecture
• WebLogic Server provided JDBC driver types
• Data Source definition and workings
• Connection pool definition and workings
• Managing JDBC resources with the Administration Console.

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