executeQuery模板方法

package march.part0320.dao.impl;

import march.part0320.dao.UserDao;
import march.part0320.entity.User;
import march.part0320.util.DateUtil;
import march.part0320.util.JdbcTemplate;
import march.part0320.util.JdbcUtil;

import java.sql.*;

public class UserDaoImpl implements UserDao {
    @Override
    public void add(User user) {
        String sql = "insert into t_user(t_username,t_pwd,t_createtime) values (?,?,now())";
        JdbcTemplate.executeUpdate(sql,user.getUserName(),user.getPwd());
    }

    
    @Override
    //希望做成模板
    public User query(String userName, String pwd) {
        User user = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        Connection connection = null;
        connection = JdbcUtil.getConnection();
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        //也有可能select···from dept
        //模板：大部分相同一些地方不相同
        //SQL、参数、O/R Mapping的格式不一样
        String sql = "select t_username,t_pwd,t_createtime from t_user where t_username = ? and t_pwd = ?";
        try {
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,userName);
            preparedStatement.setString(2,pwd);
            //参数可能不一样
            resultSet = preparedStatement.executeQuery();
            if (resultSet.next()) {
                //O/R Mapping的过程
                user = new User(resultSet.getString("t_username"),resultSet.getString("t_pwd"), DateUtil.strToDate(resultSet.getString("t_createtime"),"yyyy-MM-dd HH:mm:ss"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtil.close(resultSet,preparedStatement,connection);
        }
        return user;
    }
}

在JdbcTemplate中添加统一的查询方法

package march.part0320.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class JdbcTemplate {
    
    public static void executeUpdate(String sql,Object ... preparedStatements) {
        Connection connection = null;
        connection = JdbcUtil.getConnection();
        PreparedStatement preparedStatement = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            setPreparedStatements(preparedStatement,preparedStatements);
            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtil.close(preparedStatement,connection);
        }
    }

    private static void setPreparedStatements(PreparedStatement preparedStatement,Object ... preparedStatements) {
        if (!(null == preparedStatement || preparedStatements.length == 0)) {//有参数
            for (int i = 0 ; i < preparedStatements.length ; i++) {
                try {
                    preparedStatement.setObject((i + 1),preparedStatements[i]);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static List