在Java中动态传递SQL查询结果作为方法参数的教程

public static List<Map<String, Object>> getResultInMapList(String urlString, String driverr,
                                                            String usernameString, String password,
                                                            String sqlQuery, Object... params) throws SQLException, IOException {
    try {
        createConn(urlString, driverr, usernameString, password);
        if (params == null || params.length == 0) {
            return run.query(conn, sqlQuery, new MapListHandler());
        } else {
            return run.query(conn, sqlQuery, new MapListHandler(), params);
        }
    } catch (SQLException se) {
        se.printStackTrace();
        return null;
    } finally {
        closeConn();
    }
}

import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
// 假设 createConn, closeConn, run (DbUtils QueryRunner), MapListHandler 已定义

public class QueryParameterExample {

    // 假设 conn 是一个已建立的数据库连接
    private static Connection conn; 

    // ... 其他辅助方法如 createConn, closeConn, run ...

    public static void main(String[] args) throws SQLException, IOException {
        String urlString = "jdbc:mysql://localhost:3306/testdb";
        String driverr = "com.mysql.cj.jdbc.Driver";
        String usernameString = "user";
        String password = "password";
        String sqlQuery = "SELECT id, value FROM another_table WHERE name IN (?)"; // 示例主查询
        String sqlQuery2 = "SELECT name FROM fake_table WHERE status = 'active'"; // 参数生成查询

        List<Object> paramList = new ArrayList<>();

        // 建立连接 (假设 createConn 能够返回 Connection 对象或设置全局 conn)
        // 这里简化处理，实际应用中应确保 conn 已正确初始化
        createConn(urlString, driverr, usernameString, password); 

        try (Statement statement = conn.createStatement()) {
            ResultSet results = statement.executeQuery(sqlQuery2);
            while (results.next()) {
                // 假设 sqlQuery2 只返回一个列，且该列是我们需要传递的参数
                paramList.add(results.getString(1)); 
            }
        } catch (SQLException e) {
            System.err.println("Error executing parameter generation query: " + e.getMessage());
            e.printStackTrace();
            return; // 错误处理
        } finally {
            // 注意：这里的 closeConn() 应该在所有数据库操作完成后执行，或者在 try-with-resources 外部管理
            // 为了示例清晰，暂时放在这里
            // closeConn(); 
        }

        // ... 后续步骤
    }

    // 示例辅助方法，实际项目中应有更完善的连接管理
    private static void createConn(String url, String driver, String user, String pass) throws SQLException {
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, user, pass);
            System.out.println("Connection established.");
        } catch (ClassNotFoundException e) {
            System.err.println("JDBC Driver not found: " + driver);
            throw new SQLException("JDBC Driver not found", e);
        }
    }

    private static void closeConn() {
        if (conn != null) {
            try {
                conn.close();
                System.out.println("Connection closed.");
            } catch (SQLException e) {
                System.err.println("Error closing connection: " + e.getMessage());
            }
        }
    }

    // 假设 run 是 Apache DbUtils 的 QueryRunner 实例
    // 假设 MapListHandler 是 Apache DbUtils 的 ResultSetHandler
    // 为了示例，这里简化 DbUtils 的使用
    private static class DbUtilsQueryRunner {
        public List<Map<String, Object>> query(Connection conn, String sql, MapListHandler handler, Object... params) throws SQLException {
            // 模拟 DbUtils 的查询逻辑
            System.out.println("Executing query: " + sql + " with params: " + java.util.Arrays.toString(params));
            // 实际中这里会执行 PreparedStatement 并处理结果
            // For demonstration, return an empty list or mock data
            return new ArrayList<>(); 
        }
        public List<Map<String, Object>> query(Connection conn, String sql, MapListHandler handler) throws SQLException {
             System.out.println("Executing query: " + sql + " with no params.");
             return new ArrayList<>();
        }
    }
    private static DbUtilsQueryRunner run = new DbUtilsQueryRunner();
    private static class MapListHandler implements org.apache.commons.dbutils.ResultSetHandler<List<Map<String, Object>>> {
        @Override
        public List<Map<String, Object>> handle(ResultSet rs) throws SQLException {
            // 模拟处理结果集
            return new ArrayList<>();
        }
    }
}

// 承接上一步的代码
// ... (之前的代码，包括 paramList 的填充)

        Object[] params = paramList.toArray();

        // 调用目标方法
        List<Map<String, Object>> resultSet = null;
        try {
            resultSet = getResultInMapList(urlString, driverr, usernameString, password, sqlQuery, params);
            System.out.println("Result Set from main query: " + resultSet);
        } catch (SQLException | IOException e) {
            System.err.println("Error executing main query: " + e.getMessage());
            e.printStackTrace();
        } finally {
            closeConn(); // 确保在所有操作完成后关闭连接
        }
    }
    // ... (getResultInMapList 和其他辅助方法)
}