一、安装HadoopHadoop集群需要java环境支持，所以要提前安装好并配置好JDK。Hadoop下载地址https://www. oracle. com/technetwork/java/javase/downloads/index. html。在第一台虚拟机上（Hadoop-01）将下载完毕的Hadoop（我的是2.7.4的版本）安装包上传至Linux系统的/export/software

报错信息：Installation did not succeed.The application could not be installed: INSTALL_FAILED_OLDER_SDKList of apks:[0] 'E:\WorkSpaces\Android\MusicService\app\build\outputs\apk\debug\app-debug.apk'The app

【代码】npm run serve 报错： ERROR TypeError: transpileDependencies.map is not a functionTypeError: transpil。

最近在做瑞吉外卖的时候就遇到了这个问题，写过滤器处理请求的时候判断是否登录时request.getSession().getAttribute("employee")获得了空值//4 判断是否登录 已登录则放行if(request.getSession().getAttribute("employee")!=null){log.info("用户已登录，id为{}",request.getSessi