BaseDao的封装（更新操作和查询操作）

package com.liujinghe.util;

import org.apache.commons.beanutils.BeanUtils;

import java.lang.reflect.InvocationTargetException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class BaseDao6 {
    //增删改
    public int update(String sql,Object [] parameters) throws SQLException {
        //获取数据库链接对象
        Connection connection = JdbcUtil6.getConnection();
        //获取预处理sql语句搬运工
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        //获取参数元数据
        ParameterMetaData parameterMetaData = preparedStatement.getParameterMetaData();
        //获取参数个数
        int parameterCount = parameterMetaData.getParameterCount();
        //占位符具体化
        if(parameters!=null && parameterCount==parameters.length){
            for (int i = 1; i <= parameterCount; i++) {
                preparedStatement.setObject(i,parameters[i-1]);
            }
        }
        //执行sql语句
        int i = preparedStatement.executeUpdate();
        //关闭流资源
        JdbcUtil6.close(connection,preparedStatement);
        System.out.println(i);
        //返回受影响的行数
        return i;
    }
    //查询
    public<T> List<T> query(String sql,Object [] parameters, Class<T> cls) throws SQLException {
        //1.获取数据库连接对象
        Connection connection = JdbcUtil6.getConnection();
        //2.获取预处理sql语句搬运工
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        //3.获取参数元数据对象
        ParameterMetaData parameterMetaData = preparedStatement.getParameterMetaData();
        //4.获取参数个数
        int parameterCount = parameterMetaData.getParameterCount();
        //5.占位符具体化
        if(parameters!=null && parameterCount==parameters.length){
            for (int i = 1; i <= parameterCount; i++) {
                preparedStatement.setObject(i,parameters[i-1]);
            }
        }
        //6.执行sql语句
        ResultSet resultSet = preparedStatement.executeQuery();
        //7.获取结果集元数据
        ResultSetMetaData metaData = resultSet.getMetaData();
        //15.创建集合
        ArrayList<T> list = new ArrayList<>();
        //8.遍历数据
        while (resultSet.next()){
            //9.获取列的个数
            int columnCount = metaData.getColumnCount();
            //13.创建当前类对象
            T t =null;
            try {
                t = cls.getConstructor(null).newInstance(null);
                //10.获取列的名字
                for (int i = 1; i <= columnCount; i++) {
                    String columnName = metaData.getColumnName(i);
                    //11.获取列的值
                    Object value = resultSet.getObject(columnName);
                    //12.将值赋值给当前类对象
                    BeanUtils.setProperty(t,columnName,value);
                }
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            }
            //14.将类对象数据存入集合中
            list.add(t);
        }
        //16.关闭流资源
        JdbcUtil6.close(connection,preparedStatement,resultSet);
        //17.遍历集合
        for (T t : list) {
            System.out.println(t);
        }
        //18.返回集合
        return list;
    }
}