Java Database Connectivity

1. Java Database Connectivity B.Ramamurthy B.Ramamurthy

2. Introduction • Most popular form of database system is the relational database system. • Examples: MS Access, Sybase, Oracle, MS Sequel Server. • Structured Query Language (SQL) is used among relational databases to construct queries. • These queries can be stand-alone or embedded within applications. This form of SQL is known as embedded SQL. B.Ramamurthy

3. A P P L I C A T I O N DBMS DB Simple Database Application Ex: Access Oracle Sybase B.Ramamurthy

4. Multi-Databases A P P L I C A T I O N DBMS 1 DB DBMS 2 DB DBMS 3 DB B.Ramamurthy

5. A P P L I C A T I O N DBMS Driver 1 D R I V E R M G R DBMS 1 DB DBMS Driver 2 DBMS 2 DB DBMS Driver 3 DBMS 3 DB Standard Access to DB B.Ramamurthy

6. DriverType1 DriverType2 DriverType3 ODBC Architecture Application Class1 Class2 ODBC Driver Manager DataSource3 DataSource2 DataSource1 B.Ramamurthy

7. Open Database Connectivity (ODBC) Standard • ODBC standard is an interface by which application programs can access and process SQL databases in a DBMS-independent manner. It contains: • A Data Source that is the database, its associated DBMS, operating system and network platform • A DBMS Driver that is supplied by the DBMS vendor or independent software companies • A Driver Manager that is supplied by the vendor of the O/S platform where the application is running B.Ramamurthy

8. ODBC Interface • It is a system independent interface to database environment that requires an ODBC driver to be provided for each database system from which you want to manipulate data. • The database driver bridges the differences between your underlying system calls and the ODBC interface functionality. B.Ramamurthy

9. An Example odbc standard API Application DriverManager Sybase driver mSQL driver Informix driver B.Ramamurthy

10. Application in Java jdbc API odbc standard API Application in Java DriverManager Sybase driver mSQL driver Informix driver B.Ramamurthy

11. Java Support for ODBC : JDBC • When applications written in Java want to access data sources, they use classes and associated methods provided by Java DBC (JDBC) API. • JDBC is specified an an “interface”. • An interface in Java can have many “implementations”. • So it provides a convenient way to realize many “drivers” B.Ramamurthy

12. Java Support for SQL • Java supports embedded SQL. • Also it provides an JDBC API as a standard way to connect to common relational databases. • You need a JDBC:ODBC bridge for using the embedded SQL in Java. • Java.sql package and an extensive exception hierarchy. • We will examine incorporating this bridge using sample code. B.Ramamurthy

13. Data Source • Local relational database; Ex: Oracle • Remote relational database on a server; Ex: SQLserver • On-line information service; Ex: Dow Jones, Customer database B.Ramamurthy

14. Data Source and Driver • Data source is the data base created using any of the common database applications available. • Your system should have the driver for the database you will be using. • For example your Windows system should have the MS Access Driver. • There are a number of JDBC drivers available. • Information on installing them is available at : • http://industry.java.sun.com/products/jdbc/drivers B.Ramamurthy

15. JDBC Components • Driver Manager: Loads database drivers, and manages the connection between application & driver. • Driver: Translates API calls to operations for a specific data source. • Connection: A session between an application and a driver. • Statement: A SQL statement to perform a query or an update operation. • Metadata: Information about the returned data, driver and the database. • Result Set : Logical set of columns and rows returned by executing a statement. B.Ramamurthy

16. JDBC Classes • Java supports DB facilities by providing classes and interfaces for its components • DriverManager class • Connection interface (abstract class) • Statement interface(to be instantiated with values from the actual SQL statement) • ResultSet interface B.Ramamurthy

17. Driver Manager Class • Provides static, “factory” methods for creating objects implementing the connection interface. • Factory methods create objects on demand • when a connection is needed to a DB driver, DriverManager does it using it factory methods. B.Ramamurthy

18. Connection interface • Connection class represents a session with a specific data source. • Connection object establishes connection to a data source, allocates statement objects, which define and execute SQL statements. • Connection can also get info (metadata) about the data source. B.Ramamurthy

19. Statement interface • Statement interface is implemented by the connection object. • Statement object provides the workspace for SQL query, executing it, and retrieving returned data. • SELECT {what} FROM {table name} WHERE {criteria} ORDER BY {field} • Queries are embedded as strings in a Statement object. • Types: Statement, PreparedStatement, CallableStatement B.Ramamurthy

20. ResultSet interface • Results are returned in the form of an object implementing the ResultSet interface. • You may extract individual columns, rows or cell from the ResultSet using the metadata. B.Ramamurthy

21. Driver Driver Driver JDBC Application Architecture Application Result Set Connection Statement Driver Manager DataSource DataSource DataSource B.Ramamurthy

22. Import necessary packages; Ex: import java.sql.*; Load JDBC driver(driver should have been installed) Data source and its location should have been registered. Allocate Connection object, Statement object and ResultSet object Execute query using Statement object Retrieve data from ResultSet object Close Connection object. JDBC Programming Steps B.Ramamurthy

23. Identifying Data Sources • It is specified using URL format. • <scheme>: <sub_scheme>:<scheme-specific-part> Example(for local source): jdbc:odbc:tech_books • Alternatively, for remote connection, jdbc:odbc://bina.cse.buffalo.edu:4333/tech_books B.Ramamurthy

24. Summary • JDBC API of Java language conforms to the ODBC standard. • It supports ODBC by providing classes/interfaces for driver manager, driver, connection, statement and resultset and others. • You can access various components in JDBC by instantiating or implementing objects and accessing their methods. B.Ramamurthy