How does Java database connection use JDBC API?

Java Database Connectivity (JDBC) is an API for Java programs to interact with databases. To establish a JDBC connection, you need to: 1. Import the JDBC driver JAR file. 2. Load and register the driver. 3. Create a Connection object. JDBC allows SQL query and update operations and provides PreparedStatement for performing updates. After all operations are completed, the JDBC connection should be closed to release resources. Using JDBC, you can easily interact with the database such as inserting, querying, and updating records.

Java Database Connection: JDBC API Practical Guide

JDBC (Java Database Connectivity) is an API for Java programs to interact with databases. It provides a standard way to access different databases including MySQL, Oracle, PostgreSQL, etc.

Set up a JDBC connection

To establish a JDBC connection to the database, you need to:

1. Import the JDBC driver JAR file.
2. Load and register the driver.
3. Create a Connection object.

import java.sql.*;

public class JdbcExample {

    public static void main(String[] args) {
        // 数据库凭据
        String url = "jdbc:mysql://localhost:3306/database_name";
        String username = "root";
        String password = "password";

        // 加载和注册驱动程序
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return;
        }

        // 创建连接
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
            return;
        }

        // 使用连接执行 SQL 查询或更新操作
        // ...
    }
}

Execute SQL queries

Once the connection is established, you can execute SQL queries.

// 创建一个 Statement 对象
Statement statement = connection.createStatement();

// 执行查询并获取结果集
ResultSet resultSet = statement.executeQuery("SELECT * FROM table_name");

// 遍历结果集
while (resultSet.next()) {
    // 获取列值
    int id = resultSet.getInt("id");
    String name = resultSet.getString("name");
    
    // 打印结果
    System.out.println("Id: " + id + ", Name: " + name);
}

Performing SQL Updates

To perform SQL update operations (such as inserting, updating, or deleting records), you can use PreparedStatement.

// 创建一个 PreparedStatement
String sql = "INSERT INTO table_name (name, age) VALUES (?, ?)";
PreparedStatement statement = connection.prepareStatement(sql);

// 设置参数
statement.setString(1, "John Doe");
statement.setInt(2, 30);

// 执行更新
int rowCount = statement.executeUpdate();

Close the JDBC connection

After completing all operations, be sure to close the JDBC connection to release resources.

try {
    connection.close();
} catch (SQLException e) {
    e.printStackTrace();
}

Practical case

Suppose you have a customers table containing the following columns:

• id (ID)
• name(name)
• age(age)

Using JDBC, you can create a Java program to insert a new customer:

// 添加新客户
String sql = "INSERT INTO customers (name, age) VALUES (?, ?)";
PreparedStatement statement = connection.prepareStatement(sql);
statement.setString(1, "Jane Doe");
statement.setInt(2, 25);
int rowCount = statement.executeUpdate();

// 验证是否成功
if (rowCount > 0) {
    System.out.println("新客户已添加。");
}

Then, you can Verify that the insertion was successful by outputting the records in the customers table:

// 输出客户
ResultSet resultSet = statement.executeQuery("SELECT * FROM customers");
while (resultSet.next()) {
    int id = resultSet.getInt("id");
    String name = resultSet.getString("name");
    int age = resultSet.getInt("age");
    System.out.println("Id: " + id + ", Name: " + name + ", Age: " + age);
}

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