Java Database Connectivity Tutorial257

Java Database Connectivity (JDBC) is a Java API that provides a way for Java programs to interact with a database. JDBC is a powerful tool that can be used to perform a variety of database operations, such as creating and modifying tables, inserting and deleting data, and querying data.

In this tutorial, we will learn how to use JDBC to connect to a database, execute SQL queries, and retrieve data from a database.

Prerequisites

Before you can start using JDBC, you will need to:
Have a Java development environment installed.
Have a database server installed.
Have the JDBC driver for your database server installed.

JDBC API Overview

The JDBC API consists of a set of interfaces and classes that provide a standard way to interact with a database. The most important classes in the JDBC API are:
Connection: Represents a connection to a database.
Statement: Represents a SQL statement that can be executed on a database.
ResultSet: Represents the results of a SQL query.

Connecting to a Database

To connect to a database, you will need to use the DriverManager class. The DriverManager class provides a way to establish a connection to a database using a JDBC URL. A JDBC URL is a string that contains information about the database server, the database name, and the user credentials.

The following code shows how to connect to a database using the DriverManager class:
import ;
import ;
public class JDBCExample {
public static void main(String[] args) {
// JDBC URL
String url = "jdbc:mysql://localhost:3306/test_db";
// Username and password
String username = "root";
String password = "password";
try {
// Get a connection to the database
Connection connection = (url, username, password);
// Create a statement
Statement statement = ();
// Execute a SQL query
ResultSet resultSet = ("SELECT * FROM users");
// Process the results
while (()) {
int id = ("id");
String name = ("name");
int age = ("age");
// Print the results
(id + " " + name + " " + age);
}
// Close the statement and connection
();
();
} catch (Exception e) {
();
}
}
}

Executing SQL Queries

Once you have a connection to a database, you can use the Statement class to execute SQL queries. The Statement class provides a way to execute SQL queries and retrieve the results.

The following code shows how to execute a SQL query using the Statement class:
// Create a statement
Statement statement = ();
// Execute a SQL query
ResultSet resultSet = ("SELECT * FROM users");

Retrieving Data from a Database

Once you have executed a SQL query, you can use the ResultSet class to retrieve the results. The ResultSet class provides a way to iterate through the results of a SQL query and get the values of the columns.

The following code shows how to retrieve data from a database using the ResultSet class:
// Process the results
while (()) {
int id = ("id");
String name = ("name");
int age = ("age");
// Print the results
(id + " " + name + " " + age);
}

Closing the Connection

When you are finished using a database connection, it is important to close the connection to free up resources. You can close the connection using the close() method.

The following code shows how to close a database connection:
// Close the statement and connection
();
();

2024-11-18

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