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JDBC–JavaDatabaseConnectivity.ppt
JDBC – Java Database Connectivity Introduction to JDBC JDBC is an API, (Application Programming Interface)that is a collection of classes and interfaces. JDBC is used for accessing (mainly) databases from Java applications. Information is transferred from relations to objects and vice-versa databases optimized for searching/indexing objects optimized for engineering/flexibility JDBC Architecture JDBC Architecture (cont.) Java code calls JDBC library JDBC loads a driver Driver talks to a particular database An application can work with several databases by using all corresponding drivers Ideal: can change database engines without changing any application code (not always in practice) Seven Steps Load the driver Define the connection URL Establish the connection Create a Statement object Execute a query using the Statement Process the result Close the connection Registering the Driver To use a specific driver, we need to instantiate it and register it within the driver manager: Driver driver = new oracle.jdbc.OracleDriver(); DriverManager.registerDriver(driver); Later we’ll see why the registration is needed A Modular Alternative We can register the driver indirectly using the statement Class.forName(oracle.jdbc.driver.OracleDriver); Class.forName loads the specified class dynamically. When OracleDriver is loaded, it automatically creates an instance of itself registers this instance with the DriverManager Hence, the driver class can be given as an argument of the application An Example //?A?driver?for?imaginary1 Class.forName(ORG.img.imgSQL1.imaginary1Driver); //?A?driver?for?imaginary2 Driver?driver?=?new?ORG.img.imgSQL2.imaginary2Driver(); DriverManager.registerDriver(driver); //A?driver?for?oracle Class.forName(oracle.jdbc.driver.OracleDriver);???? Connecting to the Database Every database is identified by a URL Given a URL, DriverManager looks for the driver that can talk to the corresponding database DriverManager tries all registered drivers, until a
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