JDBC is a Java-based data access technology (Java Standard Edition platform) from Oracle Corporation. This technology is an API for the Java programming language that defines how a client may access a database. It provides methods for querying and updating data in a database. JDBC is oriented towards relational databases. A JDBC-to-ODBC bridge enables connections to any ODBC-accessible data source in the JVM host environment.

History and implementation

Sun Microsystems released JDBC as part of JDK 1.1 on February 19, 1997.^[1] It has since formed part of the Java Standard Edition.

The JDBC classes are contained in the Java package java.sql and javax.sql.

Starting with version 3.1, JDBC has been developed under the Java Community Process. JSR 54 specifies JDBC 3.0 (included in J2SE 1.4), JSR 114 specifies the JDBC Rowset additions, and JSR 221 is the specification of JDBC 4.0 (included in Java SE 6).^[2]

The latest version, JDBC 4.1, is specified by a maintenance release of JSR 221^[3] and is included in Java SE 7.^[4]

Functionality

JDBC allows multiple implementations to exist and be used by the same application. The API provides a mechanism for dynamically loading the correct Java packages and registering them with the JDBC Driver Manager. The Driver Manager is used as a connection factory for creating JDBC connections.

JDBC connections support creating and executing statements. These may be update statements such as SQL's CREATE, INSERT, UPDATE and DELETE, or they may be query statements such as SELECT. Additionally, stored procedures may be invoked through a JDBC connection. JDBC represents statements using one of the following classes:

• Statement – the statement is sent to the database server each and every time.
• PreparedStatement – the statement is cached and then the execution path is pre-determined on the database server allowing it to be executed multiple times in an efficient manner.
• CallableStatement – used for executing stored procedures on the database.

Update statements such as INSERT, UPDATE and DELETE return an update count that indicates how many rows were affected in the database. These statements do not return any other information.

Query statements return a JDBC row result set. The row result set is used to walk over the result set. Individual columns in a row are retrieved either by name or by column number. There may be any number of rows in the result set. The row result set has metadata that describes the names of the columns and their types.

There is an extension to the basic JDBC API in the javax.sql.

JDBC connections are often managed via a connection pool rather than obtained directly from the driver. Examples of connection pools include BoneCP, C3P0 and DBCP

JDBC drivers

JDBC drivers are client-side adapters (installed on the client machine, not on the server) that convert requests from Java programs to a protocol that the DBMS can understand.

Types

There are commercial and free drivers available for most relational database servers. These drivers fall into one of the following types:

• Type 1 that calls native code of the locally available ODBC driver.
• Type 2 that calls database vendor native library on a client side. This code then talks to database over network.
• Type 3, the pure-java driver that talks with the server-side middleware that then talks to database.
• Type 4, the pure-java driver that uses database native protocol.

There is also a type called internal JDBC driver, driver embedded with JRE in Java-enabled SQL databases. It's used for Java stored procedures. This does not belong to the above classification, although it would likely be either a type 2 or type 4 driver (depending on whether the database itself is implemented in Java or not). An example of this is the KPRB driver supplied with Oracle RDBMS. "jdbc:default:connection" is a relatively standard way of referring making such a connection (at least Oracle and Apache Derby support it). The distinction here is that the JDBC client is actually running as part of the database being accessed, so access can be made directly rather than through network protocols.

Sources

• SQLSummit.com publishes list of drivers, including JDBC drivers and vendors
• Oracle provides a list of some JDBC drivers and vendors
• Simba Technologies ships an SDK for building custom JDBC Drivers for any custom/proprietary relational data source
• RSSBus Type 4 JDBC Drivers for applications, databases, and web services [1].
• DataDirect Technologies provides a comprehensive suite of fast Type 4 JDBC drivers for all major database they advertise as Type 5^[5]
• IDS Software provides a Type 3 JDBC driver for concurrent access to all major databases. Supported features include resultset caching, SSL encryption, custom data source, dbShield
• OpenLink Software ships JDBC Drivers for a variety of databases, including Bridges to other data access mechanisms (e.g., ODBC, JDBC) which can provide more functionality than the targeted mechanism
• JDBaccess is a Java persistence library for MySQL and Oracle which defines major database access operations in an easy usable API above JDBC
• JNetDirect provides a suite of fully Sun J2EE certified high performance JDBC drivers.
• HSQLDB is a RDBMS with a JDBC driver and is available under a BSD license.
• SchemaCrawler^[6] is an open source API that leverages JDBC, and makes database metadata available as plain old Java objects (POJOs)

References

External links

• Java SE 7 This documentation has examples where the JDBC resources are not closed appropriately (swallowing primary exceptions and being able to cause NullPointerExceptions) and has code prone to SQL injection^{[citation needed]}
• java.sql API Javadoc documentation
• javax.sql API Javadoc documentation
• O/R Broker Scala JDBC framework
• SqlTool Open source, command-line, generic JDBC client utility. Works with any JDBC-supporting database.
• JDBC URL Strings and related information of All Databases.