Connection Interface in Java JDBC

The Connection interface in Java JDBC represents a session between a Java application and a database. It is used to establish communication, execute SQL queries, and manage transactions. It acts as a bridge that enables interaction with the database.

• Used to establish a connection with the database
• Acts as a bridge between Java application and database
• Supports transaction management (commit, rollback)
• Provides methods to create statement objects

Architecture Flow

This diagram illustrates how a Java application interacts with a database using JDBC components:

• The Java Application sends a SQL query using a Statement object
• The JDBC Driver acts as a translator and converts Java calls into database-specific commands
• The Connection establishes a link between the application and the database
• The Database executes the SQL query and returns the result
• The result is stored in a ResultSet, which is then sent back to the application

How to Obtain a Connection?

A Connection object is created using the DriverManager class:

Connection con = DriverManager.getConnection(url, username, password);

Important Methods of Connection Interface

1. createStatement(): Creates a Statement object to execute SQL queries.

Statement stmt = con.createStatement();

2. prepareStatement(String sql): Creates a PreparedStatement for parameterized queries.

PreparedStatement ps = con.prepareStatement("SELECT * FROM student WHERE id = ?");

3. prepareCall(String sql): Creates a CallableStatement for stored procedures.

CallableStatement cs = con.prepareCall("{call procedure_name()}");

4. setAutoCommit(boolean status): Controls auto-commit mode.

con.setAutoCommit(false);

5. commit(): Saves the transaction permanently.

con.commit();

6. rollback(): Reverts changes in case of failure.

con.rollback();

7. close(): Closes the database connection.

con.close();

Example Code:

import java.sql.Connection;
import java.sql.DriverManager;

class ConnectionDemo {
    public static void main(String[] args) {
        try {
            Connection con = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/test",
                "root",
                "password"
            );

            System.out.println("Connection Established Successfully!");

            con.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Working of Connection Interface

1. The Java application sends a request (SQL query)
2. The Connection establishes a link with the database
3. The JDBC driver translates the request
4. The database processes the query
5. The result is returned to the application