Steps to Connect a Java Application to Database
There are following five steps to create the database connection with Java application:1. Register the Driver
2. Create Connection
3. Create SQL Statement
4. Execute SQL Queries
5. Close the Connection
1. Register the driver
The Class.forName() method is used to register the driver class dynamically.For example:
Class.forName("oracle.jdbc.odbc.JdbcOdbcDriver");
2. Create the Connection Object
The DriverManager class provides the getConnection() method to establish connection object. It requires to pass a database url, username and password.Syntax
getConnection(String url);
getConnection(String url, String username, String password);
getConnection(String url, Properties Info);
Example : Creating connection with oracle driver
Connection con = DriverManager.getConnection ("jdbc:oracle:thin:@localhost:1521:XE","username","password");
3. Create SQL Statement
The Connection interface provides the createStatement() method to create SQL statement.Syntax:
public Statement createStatement( ) throws SQLException
Example:
Statement stmt = con.createStatement();
4. Execute SQL Queries
The Statement interface provides the executeQuery( ) method to execute SQL statements.Syntax:
public ResultSet executeQuery(String sql) throw SQLException
Example
ResultSet rs = stmt.executeQuery("select * from students");
while (rs.next())
{
System.out.println (rs.getInt(1)+" "+rs.getString(2)+" "+rs.getFloat(3));
}
5. Closing the Connection
The Connection interface provides close( ) method, used to close the connection. It is invoked to release the session after execution of SQL statement.Syntax:
public void close( ) throws SQLException
Example:
con.close( );
Note: We will discuss whole program in JDBC using oracle database with type 4 (Thin) driver.
Example : Connect the Java application with Oracle database
import java.sql.*;
class JDBCDemo
{
public static void main(String args[])
{
try
{
//Load the driver
Class.forName("oracle.jdbc.driver.OracleDriver");
//Cretae the connection object
Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","scott", "tiger");
//Create the Statement Object
Statement stmt = con.createStatement();
//Excute the SQL query
ResultSet rs = stmt.executeQuery("Select * from students");
while (rs.next())
{
System.out.println (rs.getInt(1)+" "+rs.getString(2)+" "+rs.getFloat(3));
}
//Closing the connection object
con.close();
stmt.close();
rs.close();
}
catch(Exception e)
{
System.out.println(e);
}
}
}
