Tomcat异常之——启动报错Failed to start component
在idea中运行tomcat时，遇到异常，异常信息如下：
16-Jan-2018 16:33:37.325 信息 [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDescriptor Deploying configuration descriptor C:\Users\Administrator\.IntelliJIdea2017.1\system\tomcat\Unnamed_xxx_6\conf\Catalina\localhost\AAA.xml
16-Jan-2018 16:33:37.331 警告 [localhost-startStop-1] org.apache.catalina.startup.SetContextPropertiesRule.begin [SetContextPropertiesRule]{Context} Setting property 'debug' to '0' did not find a matching property.
16-Jan-2018 16:33:37.336 严重 [localhost-startStop-1] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start:
org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/AAA]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:753)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:729)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:621)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1835)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [org.apache.catalina.webresources.StandardRoot@1f063757]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:162)
at org.apache.catalina.core.StandardContext.resourcesStart(StandardContext.java:4969)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5102)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
... 10 more
Caused by: java.lang.IllegalArgumentException: The main resource set specified [G:\AAA] is not valid
at org.apache.catalina.webresources.StandardRoot.createMainResourceSet(StandardRoot.java:746)
at org.apache.catalina.webresources.StandardRoot.startInternal(StandardRoot.java:704)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
... 13 more
16-Jan-2018 16:33:37.338 严重 [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDescriptor Error deploying configuration descriptor C:\Users\Administrator\.IntelliJIdea2017.1\system\tomcat\Unnamed_xxx_6\conf\Catalina\localhost\AAA.xml
java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/AAA]]
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:757)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:729)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:621)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1835)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
网上各种答案：1）tomcat与jdk版本不匹配；2）maven版本冲突；3）web.zml中配置错误；4）tomcat有缓存.........我都尝试了都没有解决我的问题。
由于我在tomcat中配置了虚拟路径（什么是虚拟路劲，怎么设置请看http://blog.csdn.net/zjml2412/article/details/49962939），就是在tomcat的安装目录conf\Catalina\localhost下新建了一个配置文件AAA.xml文件，文件具体内容为：
<?xml version="1.0" encoding="UTF-8"?>
<Context docBase="G:/AAA" reloadable="true" debug="0" path="/AAA"/>
其中“G:/AAA”代表我的电脑磁盘的G盘有个AAA文件，tomcat在启动的时候会加载“G:/AAA”文件夹（文件），以便可以在网络上使用"/AAA"访问，所以说如果G盘没有AAA文件夹（文件），tomcat启动时会出现上面的异常。
所以说出现上面的异常，1）如果你配置过虚拟路径，并且项目中要用到虚拟路径，那么请先在对应的”G”盘创建”AAA”文件；2）如果没有配置过虚拟路劲，出现上面的异常，你可以将conf\Catalina\localhost的文件删除；实在不行，网上下载一个新的tomcat部署项目应该就好了。
