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6.2.1 Relational Database Integration Technologies

Relational database management systems (RDBMS) are the most prevalent form of

enterprise data store. The J2EE platform provides three technologies for integrating

data in RDBMS: 

  JDBC Developers can use the JDBC APIs to access relational data in a tab 

ular form. 

  Enterprise JavaBeans container managed persistence (CMP) Developers use 

container managed persistence to do object relational (O/R) mapping. By 

mapping database table data to Java objects, developers can deal with an object 

view of the data rather than a tabular, relational view. CMP also encapsulates 

the objects into higher level managed components with transactional and secu 

rity features. 

  Java Data Objects (JDO) An O/R mapping technology that generates Java 

classes as opposed to components. Note that JDO is optional in the J2EE 1.4 

platform. Since it is optional, your application server may not support JDO, or 

it may support JDO in a nonstandard manner.

 Data Mapping in EAI Applications  on page 274 explains when it is better to

use JDBC, enterprise beans, or JDO.

6.2.1.1

JDBC

The JDBC API defines a standard Java API for integration with relational data 

base systems. A Java application uses the JDBC API for obtaining a database con 

nection, retrieving database records, executing database queries and stored

procedures, and performing other database functions.

Many application component providers use the JDBC API for accessing rela 

tional databases to manage persistent data for their applications. 

The JDBC API has two parts: a client API for direct use by developers to

access relational databases and a standard, system level contract between J2EE

servers and JDBC drivers for supporting connection pooling and transactions.

Developers do not use the contract between J2EE servers and JDBC drivers

directly. Rather, J2EE server vendors use this contract to provide pooling and

transaction services to J2EE components automatically. Note that, according to

the JDBC 3.0 specification, the JDBC system level contracts can be the same as

the Connector architecture system contracts. Conceptually, JDBC drivers are