jdbc连接数据库代码

Sure, here's a simple example of Java code using JDBC to connect to a MySQL database. Make sure you have the MySQL JDBC driver (JAR file) in your classpath.

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

public class DatabaseConnectionExample {

    public static void main(String[] args) {
        // JDBC URL, username, and password of MySQL server
        String url = "jdbc:mysql://localhost:3306/your_database_name";
        String user = "your_username";
        String password = "your_password";

        // Establishing the connection
        try (Connection connection = DriverManager.getConnection(url, user, password)) {
            System.out.println("Connected to the database!");

            // Perform database operations here

        } catch (SQLException e) {
            System.err.println("Connection failed. Error: " + e.getMessage());
        }
    }
}

Remember to replace "your_database_name," "your_username," and "your_password" with your actual database name, username, and password.

Make sure you have the MySQL JDBC driver in your classpath. You can download it from the official MySQL website: https://dev.mysql.com/downloads/connector/j/

If you're using a different database, you'll need to change the JDBC URL accordingly. Additionally, make sure to handle exceptions appropriately in a production environment.

Certainly! Here's an extension to the previous example, including a simple query execution:

java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DatabaseConnectionExample {

    public static void main(String[] args) {
        // JDBC URL, username, and password of MySQL server
        String url = "jdbc:mysql://localhost:3306/your_database_name";
        String user = "your_username";
        String password = "your_password";

        // Establishing the connection
        try (Connection connection = DriverManager.getConnection(url, user, password)) {
            System.out.println("Connected to the database!");

            // Performing a simple query
            String query = "SELECT * FROM your_table_name";
            try (PreparedStatement preparedStatement = connection.prepareStatement(query);
                 ResultSet resultSet = preparedStatement.executeQuery()) {

                // Processing the result set
                while (resultSet.next()) {
                    // Retrieve data from the result set
                    int id = resultSet.getInt("id");
                    String name = resultSet.getString("name");

                    // Print the data
                    System.out.println("ID: " + id + ", Name: " + name);
                }

            } catch (SQLException e) {
                System.err.println("Error executing query. Error: " + e.getMessage());
            }

        } catch (SQLException e) {
            System.err.println("Connection failed. Error: " + e.getMessage());
        }
    }
}

In this example, I added a simple query to select all records from a table. Make sure to replace "your_table_name" with the actual name of your table.

Remember to handle exceptions appropriately in a production environment and close resources properly. Additionally, you might need to adjust the SQL query and result processing based on your specific database schema and requirements.