老师打开http://localhost:8080/admin/Catalog/list.do空指针异常

老师打开http://localhost:8080/admin/Catalog/list.do空指针异常

java.lang.NullPointerException

at com.imooc.icake.global.DaoFactory.getDao(DaoFactory.java:27)

at com.imooc.icake.biz.Impl.CatelogBizImpl.<init>(CatelogBizImpl.java:12)

at com.imooc.icake.controller.CatalogController.<init>(CatalogController.java:16)

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

at java.lang.Class.newInstance(Class.java:442)

at com.imooc.icake.global.GlobalController.service(GlobalController.java:52)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at com.imooc.icake.global.EncodingFilter.doFilter(EncodingFilter.java:25)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)

at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)

at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)

at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)

at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1634)

at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

at java.lang.Thread.run(Thread.java:748)

java.lang.NullPointerException

at com.imooc.icake.global.DaoFactory.getDao(DaoFactory.java:27)

at com.imooc.icake.biz.Impl.CatelogBizImpl.<init>(CatelogBizImpl.java:12)

at com.imooc.icake.controller.CatalogController.<init>(CatalogController.java:16)

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

at java.lang.Class.newInstance(Class.java:442)

at com.imooc.icake.global.GlobalController.service(GlobalController.java:52)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at com.imooc.icake.global.EncodingFilter.doFilter(EncodingFilter.java:25)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)

at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)

at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)

at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)

at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)

at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1634)

at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

at java.lang.Thread.run(Thread.java:748)

04-Feb-2021 14:26:18.557 信息 [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory 把web 应用程序部署到目录 [E:\jar包\tomcat\apache-tomcat-8.5.61\webapps\manager]

04-Feb-2021 14:26:18.572 信息 [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Web应用程序目录[E:\jar包\tomcat\apache-tomcat-8.5.61\webapps\manager]的部署已在[15]毫秒内完成
慕九州5281120 2021-02-04
源自：项目：商品信息管理   3-2 分类管理表现层
23
收起

正在回答

登陆购买课程后可参与讨论，去登陆吧

2回答
好帮手慕阿满 回答被采纳获得+3积分 2021-02-04 15:41:12

同学你好，这里需要去掉try中的SqlSessionFactory，三个sessionFactory是同一个对象，try中的sessionFactory是初始化sessionFactory，如果try中重新定义了sessionFactory，那么getDao()方法中的sessionFactory没有初始化，也就是null，使用其调用方法时就会出现空指针异常。

http://img1.sycdn.imooc.com//climg/601ba49d0987cadf06450487.jpg

祝学习愉快~

0
收起回答
好帮手慕阿满 2021-02-04 15:07:21

同学你好，报错提示是空指针异常，错误出现在DaoFactory类的27行，getDao()方法中，如：

http://img1.sycdn.imooc.com//climg/601b9c860900bb1a07540139.jpg

​建议同学检查一下sessionFactory是否正确加载，如：

http://img1.sycdn.imooc.com//climg/601b9cf8092ba64412310542.jpg

如果同学检查没错，建议同学将代码贴上来，另外建议将项目展开截图贴一下。

祝学习愉快~

0
收起回答
  • 提问者 慕九州5281120 #1 
    package com.imooc.icake.global;

    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;

    import java.io.IOException;

    public class DaoFactory {
        private static DaoFactory daoFactory;
        private SqlSessionFactory sessionFactory;
        private DaoFactory(){
            SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();
            try {
                SqlSessionFactory sessionFactory = sessionFactoryBuilder.build(Resources.getResourceAsReader("/mybatis.xml"));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        public static DaoFactory getInstance(){
            if (daoFactory == null)
                daoFactory = new DaoFactory();
                return daoFactory;
            }

            public <T> T getDao(Class<T> tClass){
                return sessionFactory.openSession(true).getMapper(tClass);
            }
    }


    2021-02-04 15:16:09
  • 提问者 慕九州5281120 #2 
    package com.imooc.icake.controller;

    import com.imooc.icake.biz.CatalogBiz;
    import com.imooc.icake.biz.Impl.CatelogBizImpl;
    import com.imooc.icake.entity.Catalog;

    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;

    public class CatalogController {

        private CatalogBiz catalogBiz = new CatelogBizImpl();

        //    /admin/Catalog/list.do
        public void list(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            Catalog root = catalogBiz.getRoot();
            request.setAttribute("root",root);
            request.getRequestDispatcher("/WEB-INF/pages/admin/catalog_list.jsp").forward(request,response);
        }
        //    /admin/Catalog/toAdd.do
        public void toAdd(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
            Catalog root = catalogBiz.getRoot();
            request.setAttribute("root",root);
            request.getRequestDispatcher("/WEB-INF/pages/admin/catalog_add.jsp").forward(request,response);
        }
        //    /admin/Catalog/add.do
        public void add(HttpServletRequest request,HttpServletResponse response) throws IOException {
            String[] titles = request.getParameterValues("title");
            String[] pids = request.getParameterValues("pid");
            String[] infos = request.getParameterValues("info");
            List<Catalog> list = new ArrayList<Catalog>();
            for (int i = 0;i < titles.length;i++){
                Catalog catalog =  new Catalog();
                catalog.setTitle(titles[i]);
                catalog.setPid(Integer.getInteger(pids[i]));
                catalog.setInfo(infos[i]);
                list.add(catalog);
            }
            catalogBiz.add(list);
            response.sendRedirect("list.do");
        }
        //    /admin/Catalog/remove.do
        public void remove(HttpServletRequest request,HttpServletResponse response) throws IOException {
            int id = Integer.parseInt(request.getParameter("id"));
            catalogBiz.remove(id);
            response.sendRedirect("list.do");
        }
    }


    2021-02-04 15:16:33
  • 提问者 慕九州5281120 #3 
    package com.imooc.icake.global;

    import javax.servlet.GenericServlet;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.lang.reflect.Method;

    public class GlobalController extends GenericServlet {
        @Override
        public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {

            /*
            * .do
            * /login.do                   DefaultController  login
            * /Cake/detail.do             CakeController     detail
            * /admin/Cake/add.do          CakeController     add
            * */

            HttpServletRequest request = (HttpServletRequest) servletRequest;
            HttpServletResponse response = (HttpServletResponse) servletResponse;
            String path = request.getServletPath();
            if (path.indexOf("/admin") != -1){
                path = path.substring(7);
            }else {
                path = path.substring(1);
            }


            /*
             login.do                   DefaultController  login
             Cake/detail.do             CakeController     detail
             Cake/detail.do             CakeController     add
             * */

            int index = path.indexOf("/");
            String className = null;
            String methodName = null;
            if (index != -1){
                className = "com.imooc.icake.controller."+path.substring(0,index)+"Controller";
                methodName = path.substring(index+1,path.indexOf(".do"));
            }else {
                className = "com.imooc.icake.controller.DefaultController";
                methodName = path.substring(0,path.indexOf(".do"));
            }

            try {
                Class cla = Class.forName(className);
                Object object = cla.newInstance();
                Method method = cla.getMethod(methodName,HttpServletRequest.class,HttpServletResponse.class);
                method.invoke(object,request,response);
            }catch (Exception e){
                e.printStackTrace();
            }

        }
    }

    ​

    2021-02-04 15:17:03
点开查看后面1条评论
问题已解决，确定采纳
还有疑问，暂不采纳

恭喜解决一个难题，获得1积分~

来为老师/同学的回答评分吧

0 星

相似问题

http://localhost:8080/Catalog/list.do
1 0 1
老师，求助 添加分类提示空指针异常
0 0 4
是不是响应重定向这里写list.do和/admin/Catalog/list.do效果是一样的？
21 0 1
空指针异常
35 0 9
关于sendRedirect("list.do")
8 0 3

登录后可查看更多问答，登录/注册

3. Java 数据库开发与实战应用
  • 参与学习           人
  • 提交作业       357    份
  • 解答问题       8016    个

本阶段将带你学习MySQL数据库，JDBC接口，MyBatis框架等，带你掌握的数据的存放和管理。

了解课程

本课精华内容

问答 作业

在ldea如何创建和eclipse中Dynamic Web project 一样的

21 1

对于集合来说，能不能通过索引（数字）的方式同时插入多个字符？

22 1

老师，在集合类中我取值3，为什么结果显示是A,B，而不是C呢

22 3

centos下载问题

233 1

新的学员可以来看一下，我总结的截止到现在遇到的安装问题

114 1

查看更多本课问答
请稍等 ...
意见反馈 帮助中心 APP下载
官方微信

在线咨询

领取优惠

免费试听

领取大纲

扫描二维码，添加
你的专属老师