这几集的笔记和资料能不能补发一下下下下？老师

老师，我这个是不是缺失了job_grades这个表

SQL>

SQL> select e.last_name , e.job_id , e.salary , d.department_name , j.gra from employees e , departments d ,job_grades j where e.department_id = d.department_id and e.salary between j.lowest_sal and j.highest_sal;

老师，这些命令都要记住吗？

String g3 = new String("北京尚学堂");

为什么报错呢？

老师，我在创建文件的时候出现了问题，这个怎么解决

为啥炮弹刚接触时飞机画面暂停没有爆炸效果然后飞机消失？

老师我的这个url为什么没有返回，还有就是我之前的localhost:8080一直打开不了显示404

老师你们课程安排有点问题呀Maven里需要用到Linux  但是Maven在第一章  Linux 在第三章。这节课突然说学过Linux了一脸懵逼。。。这阶段排版是不是弄错了

老师，我这里为啥显示的是1，今天本来是星期四  按理说返回的数字应该是5啊

一、问题

使用列表推导式可以打印出九九乘法表吗，请问该怎么操作

右击显示的是图片，而不是文件内容

老师，这句话不懂什么意思。请详细解释下。

在Tomcat的host配置中，URL中的域名与虚拟主机中的不匹配，没有

交给在 Engine 中 defaultHost 指定的主机处理，老师怎么解释呢？

老师您好，在启动LivegoodsGatewayApp时，提示如下错误信息。请问这个应该如何解决呢。谢谢！

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.

2020-07-08 02:37:12.389 ERROR 84132 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.context.ApplicationContextException: Unable to start reactive web server; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'nettyReactiveWebServerFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/reactive/ReactiveWebServerFactoryConfiguration$EmbeddedNetty.class]: Unsatisfied dependency expressed through method 'nettyReactiveWebServerFactory' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'reactorServerResourceFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/reactive/ReactiveWebServerFactoryConfiguration$EmbeddedNetty.class]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: io/netty/util/AttributeKey

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:81) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:544) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:66) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at com.livegoods.gateway.LivegoodsGatewayApplication.main(LivegoodsGatewayApplication.java:13) [classes/:na]

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'nettyReactiveWebServerFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/reactive/ReactiveWebServerFactoryConfiguration$EmbeddedNetty.class]: Unsatisfied dependency expressed through method 'nettyReactiveWebServerFactory' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'reactorServerResourceFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/reactive/ReactiveWebServerFactoryConfiguration$EmbeddedNetty.class]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: io/netty/util/AttributeKey

at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:539) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.getWebServerFactory(ReactiveWebServerApplicationContext.java:111) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.createWebServer(ReactiveWebServerApplicationContext.java:89) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:78) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]

... 8 common frames omitted

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'reactorServerResourceFactory' defined in class path resource [org/springframework/boot/autoconfigure/web/reactive/ReactiveWebServerFactoryConfiguration$EmbeddedNetty.class]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: io/netty/util/AttributeKey

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1796) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1287) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1207) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

... 20 common frames omitted

Caused by: java.lang.NoClassDefFoundError: io/netty/util/AttributeKey

at reactor.netty.resources.PooledConnectionProvider.<clinit>(PooledConnectionProvider.java:204) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.resources.ConnectionProvider$Builder.build(ConnectionProvider.java:439) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.resources.ConnectionProvider.fixed(ConnectionProvider.java:331) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.resources.ConnectionProvider.fixed(ConnectionProvider.java:272) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.resources.ConnectionProvider.fixed(ConnectionProvider.java:251) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.tcp.TcpResources.create(TcpResources.java:331) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.tcp.TcpResources.getOrCreate(TcpResources.java:275) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at reactor.netty.http.HttpResources.get(HttpResources.java:42) ~[reactor-netty-0.9.5.RELEASE.jar:0.9.5.RELEASE]

at org.springframework.http.client.reactive.ReactorResourceFactory.afterPropertiesSet(ReactorResourceFactory.java:202) ~[spring-web-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1855) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1792) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

... 31 common frames omitted

Caused by: java.lang.ClassNotFoundException: io.netty.util.AttributeKey

at java.net.URLClassLoader.findClass(URLClassLoader.java:382) ~[na:1.8.0_211]

at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_211]

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_211]

at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_211]

... 42 common frames omitted

老师，这红色的报错是什么意思