JDBC. Sun Microsystems has included JDBC API as a part of J2SDK to develop Java applications that can communicate with databases.

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1 JDBC The JDBC TM API is the application programming interface that provides universal data access for the Java TM platform. In other words, the JDBC API is used to work with a relational database or other source of data in an application written in the Java programming language. The JDBC API is a Java API for accessing virtually any kind of tabular data. JDBC is the trademarked name and is not an acronym; nevertheless, JDBC is often thought of as standing for "Java Database Connectivity." The JDBC API consists of a set of classes and interfaces written in the Java programming language that provide a standard API for tool/database developers and makes it possible to write database applications using an all-java API. The value of the JDBC API is that an application can access virtually any data source and run on any platform with a Java virtual machine. Sun Microsystems has included JDBC API as a part of J2SDK to develop Java applications that can communicate with databases. JDBC Architecture: Provides the mechanism to translate Java statements into SQL statements. Can be classified into two layers: JDBC application layer JDBC driver layer JDBC Drivers: Convert SQL statements into a form that a particular database can interpret. Retrieve the result of SQL statements and convert the result into equivalent JDBC API class objects. Are of four types: JDBC-ODBC Bridge driver Native-API Partly-Java driver JDBC-Net Pure-Java driver Native Protocol Pure-Java driver

2 JDBC-ODBC bridge plus ODBC driver: The Java Software bridge product provides JDBC access via ODBC drivers. Note that ODBC binary code, and in many cases database client code, must be loaded on each client machine that uses this driver. As a result, this kind of driver is most appropriate on a corporate network where client installations are not a major problem, or for application server code written in Java in a three-tier architecture. Native-API partly-java driver: This kind of driver converts JDBC calls into calls on the client API for Oracle, Sybase, Informix, IBM DB2, or other DBMSs. Note that, like the bridge driver, this style of driver requires that some operating system-specific binary code be loaded on each client machine. JDBC-Net pure Java driver: This driver translates JDBC calls into a DBMSindependent net protocol, which is then translated to a DBMS protocol by a server. This net server middleware is able to connect its pure Java clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC alternative. It is likely that all vendors of this solution will provide products suitable for intranet use. In order for these products to support Internet access as well, they must handle the additional requirements for security, access through firewalls, and so forth, that the Web imposes. Native-protocol pure Java driver: This kind of driver converts JDBC calls directly into the network protocol used by DBMSs. This allows a direct call from the client machine to the DBMS server and is an excellent solution for intranet access. Since many of these protocols are proprietary, the database vendors themselves are the primary source. Several that are now available include Oracle, Sybase, Informix, IBM DB2, Inprise InterBase, and Microsoft SQL Server. Driver categories 3 and 4 are the preferred ways to access databases using the JDBC API. Driver categories 1 and 2 are interim solutions where direct pure Java drivers are not yet available. There are possible variations on categories 1 and 2 (not shown in the following table) that require middleware, but these are generally less desirable solutions. Categories 3 and 4 offer all the advantages of Java technology, including automatic installation (for example, downloading the JDBC driver with an applet that uses it). The commonly used classes and interfaces in the JDBC API are: DriverManager class: Loads the driver for a database. Driver interface: Represents a database driver. All JDBC driver classes must implement the Driver interface. Connection interface: Enables you to establish a connection between a Java application and a database.

3 Statement interface: Enables you to execute SQL statements. ResultSet interface: Represents the information retrieved from a database. The JDBC API classes and interfaces are available in the java.sql. The steps to create JDBC application are: Load a driver Connect to a database Create and execute JDBC statements Handle SQL exceptions Loading a Driver Using the forname() method Using the registerdriver()method Using the forname() method The forname() method is available in the java.lang.class class. The forname() method loads the JDBC driver and registers the driver with the driver manager. The method call to use the the forname() method is: Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); Using the registerdriver()method You can create an instance of the Driver class to load a JDBC driver. This instance enables you to provide the name of the driver class at run time. The statement to create an instance of the Driver class is: Driver d = new sun.jdbc.odbc.jdbcodbcdriver(); You need to call the registerdriver() method to register the Driver object with the DriverManager. The method call to register the JDBC-ODBC Bridge driver is: DriverManager.registerDriver(d);

4 Connecting to a Database The DriverManager class provides the getconnection() method to create a Connection object. The getconnection()method method has the following three forms: Connection getconnection (String <url>) Connection getconnection (String <url>, String <username>, String <password>) Connection getconnection (String <url>,properties <properties>) Creating and Executing JDBC Statements The Connection object provides the createstatement() method to create a Statement object. You can use static SQL statements to send requests to a database to retrieve results. The Statement interface contains the following methods to send static SQL statements to a database: ResultSet executequery(string str) int executeupdate(string str) boolean execute(string str) A ResultSet object maintains a cursor that enables you to move through the rows stored in a ResultSet object. Types of Result Sets The various types of ResultSet objects to store the output returned by a database are: Read only: Allows you to only read the rows in a ResultSet object. Forward only: Moves the result set cursor from first row to last row in forward direction only. Scrollable: Moves the result set cursor forward or backward through the result set. Updatable: Allows you to update the result set rows retrieved from a database table.

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