Java数据库编程：JDBC详解

概述

JDBC（Java Database Connectivity）是Java访问数据库的标准API。通过JDBC，Java程序可以连接各种关系型数据库，执行SQL语句，处理结果集。

1. JDBC连接

import java.sql.*;

public class JDBCDemo {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydb";
        String user = "root";
        String password = "123456";

        try (Connection conn = DriverManager.getConnection(url, user, password)) {
            System.out.println("数据库连接成功");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

2. CRUD操作

import java.sql.*;

public class UserDAO {
    private Connection getConnection() throws SQLException {
        return DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/mydb", "root", "123456");
    }

    public User findById(int id) {
        String sql = "SELECT * FROM users WHERE id = ?";
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setInt(1, id);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                return new User(rs.getInt("id"), rs.getString("name"), rs.getString("email"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    public int insert(User user) {
        String sql = "INSERT INTO users (name, email) VALUES (?, ?)";
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, user.getName());
            stmt.setString(2, user.getEmail());
            return stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return 0;
    }
}

3. 事务管理

import java.sql.*;

public class TransactionDemo {
    public void transfer(int fromId, int toId, double amount) {
        Connection conn = null;
        try {
            conn = getConnection();
            conn.setAutoCommit(false);

            String debitSql = "UPDATE accounts SET balance = balance - ? WHERE id = ?";
            PreparedStatement debitStmt = conn.prepareStatement(debitSql);
            debitStmt.setDouble(1, amount);
            debitStmt.setInt(2, fromId);
            debitStmt.executeUpdate();

            String creditSql = "UPDATE accounts SET balance = balance + ? WHERE id = ?";
            PreparedStatement creditStmt = conn.prepareStatement(creditSql);
            creditStmt.setDouble(1, amount);
            creditStmt.setInt(2, toId);
            creditStmt.executeUpdate();

            conn.commit();
            System.out.println("转账成功");
        } catch (SQLException e) {
            if (conn != null) {
                try { conn.rollback(); } catch (SQLException ex) { ex.printStackTrace(); }
            }
            e.printStackTrace();
        } finally {
            if (conn != null) {
                try { conn.setAutoCommit(true); conn.close(); } catch (SQLException e) { e.printStackTrace(); }
            }
        }
    }
}

4. 批处理

public void batchInsert(List<User> users) {
    String sql = "INSERT INTO users (name, email) VALUES (?, ?)";
    try (Connection conn = getConnection();
         PreparedStatement stmt = conn.prepareStatement(sql)) {
        conn.setAutoCommit(false);
        for (User user : users) {
            stmt.setString(1, user.getName());
            stmt.setString(2, user.getEmail());
            stmt.addBatch();
        }
        stmt.executeBatch();
        conn.commit();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

最佳实践

1. 使用PreparedStatement：防止SQL注入
2. 使用try-with-resources：自动关闭资源
3. 使用连接池：提高性能
4. 事务管理：保证数据一致性
5. 批处理：提高批量操作效率

总结

JDBC是Java访问数据库的基础，掌握连接、CRUD操作、事务管理和批处理，是开发数据库应用的关键。合理使用PreparedStatement和连接池，可以提高应用的性能和安全性。