Chapter 1 Introduction

What is JDBC?

JDBC (Java Database Connectivity) from the Java Software Division of Sun MicroSystems, Inc. is a specification for an application program interface (API) that allows Java applications to access multiple database management systems using Structured Query Language (SQL). The JDBC driver manager handles multiple drivers that connect to different databases.

A set of interfaces is included in the standard JDBC API so you can open connections to databases, execute SQL commands, and process results. The interfaces are described in Table 1-1.

Table 1-1: JDBC interfaces
Interface	Description
java.sql.Driver	Locates the driver for a database URL
java.sql.Connection	Connection to a specific database
java.sql.Statement	Executes SQL statements
java.sql.PreparedStatement	Handles parameterized SQL statements
java.sql.CallableStatement	Handles database stored procedure calls
java.sql.ResultSet	Gets the results of SQL statements
java.sql.DatabaseMetaData	Used to access a variety of information about a connection's DBMS and database
java.sql.ResultSetMetaData	Used to access a variety of information describing a ResultSet's attributes

Each relational database management system requires a driver to implement these interfaces. All JDBC calls are sent to the JDBC driver manager, which passes the call to the specified driver.

There are four types of JDBC drivers:

Type 1 JDBC-ODBC bridge - translates JDBC calls into ODBC calls and passes them to an ODBC driver. Some ODBC software must be resident on the client machine. Some client database code may also reside on the client machine.
Type 2 native-API partly-Java driver - converts JDBC calls into database-specific calls. This driver, which communicates directly with the database server, also requires some binary code on the client machine.
Type 3 net-protocol all-Java driver - communicates to a middle-tier server using a DBMS-independent net protocol. A middle-tier gateway then converts the request to a vendor-specific protocol.
Type 4 native-protocol all-Java driver - converts JDBC calls to the vendor-specific DBMS protocol, allowing client applications direct communication with the database server.