Distributed Application Development B. Ramamurthy

Working with Oracle Use the Oracle DBMS on UB machines. Information about this is available here.here You can access UB db from your laptop as long you have enabled VPN and installed the appropriate driver and connected the data source. (and of course you have an internet connectivity).

Standard Access to DB APPLICATIONAPPLICATION DRIVERMGRDRIVERMGR DBMS Driver 1 DBMS Driver 2 DBMS Driver 3 DBMS 1 DBMS 2 DBMS 3 DB

ODBC Architecture Application Class1Class2 Driver Manager DriverType1DriverType2DriverType3 DataSource2 DataSource1 DataSource3 ODBC

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

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.

An Example ApplicationDriverManager Access drivermySQL driverOracle driver odbc standard API

Application in Java Application in Java DriverManager Sybase drivermSQL driverInformix driver odbc standard API jdbc API

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”

Java Support for SQL Java supports embedded SQL. Also it provides an JDBC API as a standard way to connect to common relational databases. Java.sql package and an extensive exception hierarchy.

Data Source Local relational database; Ex: Oracle Remote relational database on a server; Ex: InfoSource On-line information service; Ex: Dow Jones, Customer database

SQL Statements SELECT {what} FROM {table name} SELECT {what} FROM {table name} WHERE {criteria} SELECT {what} FROM {table name} WHERE {criteria} ORDER BY {field} Others Queries are embedded as strings in a Statement object.

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.

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

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.

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.

Statement interface Statement interface is implemented by the connection object. Statement object provides the workspace for SQL query, executing it, and retrieving returned data. Types: Statement, PreparedStatement, CallableStatement

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.

JDBC Application Architecture Application Connection Driver Manager Driver DataSource Statement Result Set

JDBC Programming Steps Import necessary packages; Ex: import java.sql.*; Include jdbc classes as a jar library. Connect to the data source using “identifying” string, a user name and password. Allocate Connection object, Statement object and ResultSet object Execute query using Statement object Retrieve data from ResultSet object Close Connection object.

Identifying Data Sources It is specified using URL format. : : Example(for local source): jdbc:odbc:tech_books Alternatively, for remote connection,

Connecting to a database on Netbeans 1.Add the driver jar file to the library for inclusion during compiling and building of the executable. 2.Add a new driver (jdbc:odbc) to the databases tab. 3.Open connection to the data source (in this case to an Oracle 11g instance) 4.On successful connection you can view the data source details (tables etc.). 5.You can programmatically access the content of the database from a Java program. 6.You can execute SQL command from the source editor window.

Connecting to UB’s Oracle 11g DB Add the oracle driver to the library jars of your project. Here is the oracle driver:oracle driver In order to load the JDBC driver in your Java programs, include the line: Class.forName("oracle.jdbc.driver.OracleDriver"); try { Class.forName ("oracle.jdbc.driver.OracleDriver"); } catch (ClassNotFoundException e){ System.out.println("Could not load the JDBC driver. Check your CLASSPATH."); System.exit(0); }

Connecting to UB’s Oracle Use this connection string syntax to connect to AOS: Connection con = DriverManager.getConnection("jdbc:oracle:thin:"+user+"/"+ Rest of the programming is similar to how we programmed the Derby database..no difference!! Essentially different drivers shield the differences in the databases, exactly similar to how the device drivers operate!