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Arul .A
Arul .A

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JDBC Basics for Beginners

#java #webdev #programming

JDBC Basics for Beginners

What is JDBC?

JDBC (Java Database Connectivity) is a Java API that allows Java applications to connect with databases such as PostgreSQL, MySQL, Oracle, and SQL Server.

Using JDBC, we can:

  • Connect to a database
  • Execute SQL queries
  • Insert, update, and delete records
  • Retrieve data from tables

JDBC Architecture 

Java Application
       |
       v
     JDBC API
       |
       v
   JDBC Driver
       |
       v
    Database
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The JDBC Driver acts as a bridge between the Java application and the database.

JDBC Steps

Step 1: Load the Driver 

Class.forName("org.postgresql.Driver");
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This loads the PostgreSQL JDBC driver into memory.

Step 2: Create a Connection 

Connection con = DriverManager.getConnection(
    "jdbc:postgresql://localhost:5432/postgres",
    "postgres",
    "password"
);
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This creates a connection between Java and PostgreSQL.

Step 3: Create a Statement 

Statement stmt = con.createStatement();
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A Statement object is used to execute SQL queries.

Step 4: Execute Query 

ResultSet rs = stmt.executeQuery(
    "SELECT * FROM india_players"
);
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The query is sent to the database and the result is stored in a ResultSet.

Step 5: Read Data 

while(rs.next()) {
    System.out.println(
        rs.getString("player_name")
    );
}
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The next() method moves through each row and retrieves data.

Step 6: Close Resources 

rs.close();
stmt.close();
con.close();
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Closing resources helps prevent memory leaks.

Example Program 

import java.sql.*;

public class JdbcDemo {
    public static void main(String[] args) {

        try {

            Class.forName("org.postgresql.Driver");

            Connection con = DriverManager.getConnection(
                "jdbc:postgresql://localhost:5432/postgres",
                "postgres",
                "password"
            );

            Statement stmt = con.createStatement();

            ResultSet rs = stmt.executeQuery(
                "SELECT * FROM india_players"
            );

            while(rs.next()) {
                System.out.println(
                    rs.getString("player_name")
                );
            }

            rs.close();
            stmt.close();
            con.close();

        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}
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Important JDBC Classes

Class Purpose
DriverManager Creates database connections
Connection Represents a database connection
Statement Executes SQL queries
ResultSet Stores query results

Conclusion

JDBC is the standard API used to connect Java applications with databases. The basic JDBC flow is:

  1. Load Driver
  2. Create Connection
  3. Create Statement
  4. Execute Query
  5. Read ResultSet
  6. Close Resources

Understanding these six steps is enough to start working with JDBC and database-driven Java applications.

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