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