JavaWeb错误java.sql.SQLNonTransientConnectionException: No operations allowed after connection closed.

错误名称:连接关闭后不允许操作
无法使用调用的关闭资源,暂时把关闭资源方法注掉了
求大佬指导:
DBUtil代码如下

package cn.berchina.crm.util;


import com.mchange.v2.c3p0.ComboPooledDataSource;

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

public class DBUtil {
    //druid 连接池
//    private static DruidDataSource druidDataSource = null;
     private static ComboPooledDataSource dataSource = null;
    private  static Connection connection = null;
    private  static PreparedStatement preparedStatement = null;
    private  static ResultSet resultSet = null;
    static {
        try {
            dataSource = new ComboPooledDataSource();
//            druidDataSource = new DruidDataSource();
//            InputStream in = ClassLoader.getSystemResourceAsStream("db.properties");
//            Properties properties = new Properties();
//            properties.load(in);

//            druidDataSource.setUrl(properties.getProperty("url"));
//            druidDataSource.setUsername(properties.getProperty("user"));
//            druidDataSource.setPassword(properties.getProperty("password"));
//            druidDataSource.setUrl("jdbc:mysql://localhost:3306/crm?serverTimezone=Asia/Shanghai");
//            druidDataSource.setUsername("root");
//            druidDataSource.setPassword("123456");
//            connection= druidDataSource.getConnection();

            dataSource.setDriverClass("com.mysql.cj.jdbc.Driver");
            dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/crm?serverTimezone=Asia/Shanghai");
            dataSource.setUser("root");
            dataSource.setPassword("123456");
            connection=dataSource.getConnection();
//                Class.forName("com.mysql.jdbc.Driver");

//            Class.forName("com.mysql.cj.jdbc.Driver");
//            connection=DriverManager.getConnection("jdbc:mysql://localhost:3306/crm?serverTimezone=Asia/Shanghai","root","123456");
        } catch (Exception e){
            e.printStackTrace();
        }

    }

    /**
     * @param sql sql语句
     * @param obj Object数组存储占位符内容
     * @return 影响的数据条数
     * 添加、修改、删除一条或多条数据
     */
    public static int update(String sql, Object [] obj){
        int update = 0;
        try {
            //获取连接
//            connection = druidDataSource.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            if(obj.length > 0){
                for(int i = 0; i<obj.length; i++) {
                    preparedStatement.setObject(i+1,obj[i]);
                }
            }
            update = preparedStatement.executeUpdate();
            return update;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return update;
    }

    /**
     * @param sql sql语句
     * @param obj 条件数组
     * @return 查询到的数据结果集
     * 根据条件查询一条数据
     */
    public static ResultSet select(String sql,Object [] obj){
        try {
//            connection = druidDataSource.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            if(obj.length > 0){
                for(int i = 0; i<obj.length; i++) {
                    preparedStatement.setObject(i+1,obj[i]);
                }
            }
            resultSet = preparedStatement.executeQuery();
            return resultSet;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    public  static List selectAll(String sql , Object[] obj){
        List list = new ArrayList();
        try {
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i <obj.length; i++) {
                preparedStatement.setObject(i+1,obj[i]);
            }
            resultSet=preparedStatement.executeQuery();
            ResultSetMetaData metaData = resultSet.getMetaData();
            while (resultSet.next())
            {
                Map map =new HashMap();
                for (int i = 1; i <metaData.getColumnCount() ; i++) {
                    map.put(metaData.getColumnName(i),resultSet.getString(i));
                }
                list.add(map);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
//            close();
        }
        return list;
    }


    /**
     * 释放资源
     */
    public static void close(){
        try{
            if(resultSet != null){
                resultSet.close();
            }
            if(preparedStatement != null){
                preparedStatement.close();
            }
            if(connection != null){
                connection.close();
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
    }
}





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![在这里插入图片描述](https://img-blog.csdnimg.cn/2021012421450326.png)

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