JDBC Overview

Introduction to JDBC

• JDBC: Java Database Connectivity
• Importance of understanding JDBC despite using frameworks like Spring and Hibernate.
• Highlighted the necessity of connecting applications with databases.

Why JDBC?

• Data stored in databases cannot be accessed directly by users.
• Users need assistance to interact with databases, usually via applications.
• Applications can be built using various programming languages (Java, C#, PHP, Ruby, JavaScript).

Connecting Applications to Databases

• Applications must connect to DBMS using appropriate libraries.
• JDBC is used to connect Java applications with databases.
• Different DBMS have their own libraries for JDBC (e.g., MySQL, PostgreSQL).

Steps to Connect Java Application with Database

1. Import Packages: Import JDBC-related packages in Java.
2. Load Driver: Check if the correct driver is available (optional with JDBC 4.0).
3. Register Driver: Register the driver to be used.
4. Create Connection: Establish a connection to the database.
5. Create Statement: Prepare a SQL statement to be executed.
6. Execute Statement: Run the SQL statement and process the results.
7. Close Connection: Properly close the connection after the operations.

Example of Database Interaction

• Analogy: Calling a colleague for information.
  • Need a phone (application) and a connection (driver).
  • Dialing a number (creating a connection).
  • Asking for information (executing SQL query).
  • Closing the call (closing the connection).

Practical Implementation

• Using PostgreSQL as the database.
• Creating a new project in IntelliJ.
  • Must include the PostgreSQL JDBC driver jar file.
• Writing SQL queries to fetch data (e.g., retrieving product names based on IDs).

JDBC Code Steps

1. Load the driver (optional).
2. Establish a connection using DriverManager.
3. Create a statement object.
4. Execute the SQL query using executeQuery method.
5. Process the ResultSet to obtain data.
6. Handle exceptions properly (try-catch recommended).
7. Close the connection to avoid resource leaks.

Handling ResultSet

• ResultSet behaves like a cursor pointing to data:
  • Must call next() to move the pointer before accessing data.
  • Example of accessing a single result from a query.

Best Practices

• Always handle exceptions properly.
• Avoid hardcoding sensitive information like usernames and passwords.
• Use PreparedStatement to prevent SQL injection attacks when dealing with dynamic values.

Conclusion

• Understanding JDBC is crucial for effective database management in Java applications.
• Provides a foundation for using high-level frameworks like Spring with ORM.