我的mysql版本是8.0的，这个connecterjar包是不是版本太低？还有配置里面C3P0连接池缺少东西吗？我现在写的代码，用户名和密码登录不上，然后后台分类列表的代码运行报出gategoryServlet.findAll() 空指针，反复看了几遍代码应该是没有问题！不知道是不是配置问题？谢谢

这是访问http://localhost:8080/shop/CategoryServlet?method=findAll  时候的报错

package com.imooc.web.action;

import java.io.IOException;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.imooc.domain.Category;

import com.imooc.service.CategoryService;

import com.imooc.service.impl.CategoryServiceImpl;

/**

 * Servlet implementation class CategoryServlet

 */

@WebServlet("/CategoryServlet")

public class CategoryServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//请求路径：localhost:8080/shop/CategoryServlet?method=findAll

String methodName=request.getParameter("method");

if("findAll".equals(methodName)) {

//查询所有分类

findAll(request,response);

}

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);

}

/**

* 后台分类管理查询所有分类的方法

* @param request

* @param response

*/

private void findAll(HttpServletRequest request, HttpServletResponse response) {

//接受参数

//封装数据

//调用业务层处理数据

System.out.println("CategoryServlet的findAll方法执行了。。。");

CategoryService categoryService=new CategoryServiceImpl();

List<Category> list=categoryService.findAll();

for(Category category:list) {

System.out.println(category);

}

//页面跳转

}

}

报错代码！麻烦了