java.sql.SQLException异常原因排查与解决

CREATE TABLE users (
    id BIGINT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(50) NOT NULL,
    age INT
);

String sql = "SELECT * FROM users WHERE username = ? AND age = ?";
PreparedStatement ps = connection.prepareStatement(sql);
ps.setString(1, "zhangfei");
ps.setInt(2, 18);

ResultSet rs = ps.executeQuery();

import java.sql.*;
import java.util.Arrays;

public class JdbcHelper {

    public static void executeQuery(Connection conn, String sql, Object... params) {
        try (PreparedStatement ps = conn.prepareStatement(sql)) {

            // 参数绑定
            for (int i = 0; i < params.length; i++) {
                ps.setObject(i + 1, params[i]);
            }

            // 打印完整 SQL
            System.out.println("Executing SQL: " + buildFullSql(sql, params));

            try (ResultSet rs = ps.executeQuery()) {
                while (rs.next()) {
                    System.out.println("User: " + rs.getString("username") + ", Age: " + rs.getInt("age"));
                }
            }

        } catch (SQLException e) {
            System.err.println("SQL 执行异常: " + e.getMessage());
            e.printStackTrace();
        }
    }

    // 将参数替换到 SQL 中（简易版）
    private static String buildFullSql(String sql, Object... params) {
        String fullSql = sql;
        for (Object param : params) {
            String value = (param instanceof String) ? "'" + param + "'" : String.valueOf(param);
            fullSql = fullSql.replaceFirst("\\?", value);
        }
        return fullSql;
    }

    // Demo 入口
    public static void main(String[] args) throws Exception {
        Connection conn = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/testdb", "root", "password");

        executeQuery(conn, "SELECT * FROM users WHERE username = ? AND age = ?", "zhangfei", 18);
    }
}