Table of Contents
JDBC (‘Java Database Connectivity’) allows multiple implementations to exist and be used by the same application.
Steps for connection
Let have a look at how an application is connected to the database in java.
-
Loading a Driver
A program can also explicitly load JDBC drivers at any time. The forName() method of Class class is used to register the driver class. This method is used to dynamically load the driver class.
Syntax of forName() method
public static void forName(String className)
throws ClassNotFoundException
Example to register the mySql.Driver class
Class.forName(“mysql.Driver”); -
Establishing connection
The getConnection() method of DriverManager class is used to establish connection with the database.
Syntax of getConnection() method
DriverManager.getConnection (url,user,password);
Example to establish connection with the MySql database
Connection con=DriverManager.getConnection (“jdbc:mysql://localhost:3306/dbl”,”root”,”password”); -
Preparing Statement
The createStatement() method of Connection interface is used to create statement. The object of statement is responsible to execute queries with the database.
Syntax of createStatement() method
public Statement createStatement()throws SQLException
Example to create the statement object
Statement stmt=con.createStatement(); -
Executing Statement
PreparedStatement has several method to execute query.
1.execute()
2.executeQuery
3.executeUpdate -
Getting results
The executeQuery() method of Statement interface is used to execute queries to the database. This method returns the object of ResultSet that can be used to get all the records of a table.
Syntax of executeQuery() method
public ResultSet executeQuery(String sql)throws SQLException
Example to execute query
ResultSet rs=stmt.executeQuery(“select * from emp”);
while(rs.next()){
System.out.println(rs.getInt(1)+” “+rs.getString(2));
} -
Closing Database Connection
By closing connection object statement and ResultSet will be closed automatically. The close() method of Connection interface is used to close the connection.
Syntax of close() method
public void close()throws SQLException
Example to close connection
con.close();
JDBC Connection Example
Let’s have a look at the below example program.We are connecting to an Oracle database and getting data from emp table. Here, system and oracle are the username and password of the Oracle database.
import java.sql.*;
class Oracleconnection{
public static void main(String args[]){
try{
//step1 load the driver class
Class.forName("oracle.jdbc.driver.OracleDriver");
//step2 create the connection object
Connection con=DriverManager.getConnection( "jdbc:oracle:thin:@localhost:1521:xe","system","oracle");
//step3 create the statement object
Statement stmt=con.createStatement();
//step4 execute query
ResultSet que=stmt.executeQuery("select * from emp");
while(rs.next())
System.out.println(que.getInt(1)+" "+que.getString(2)+" "+que.getString(3));
//step5 close the connection object
con.close();
}catch(Exception e){ System.out.println(e);}
}
} 