其實之前就遇到一次這樣問題，但還是因記性，，所以開始記錄自己的Error。

**出現問題：**Application Server was not connected before run configuration stop, reason: Unable to ping server at localhost:1099

Output：
“G:\Program Files (x86)\JetBrains\apache-tomcat-9.0.0.M17\bin\catalina.bat” run
[2017-03-13 09:47:13,693] Artifact WebApp:war exploded: Server is not connected. Deploy is not available.
The JRE_HOME environment variable is not defined correctly
This environment variable is needed to run this program
Disconnected from server

問題出現及解決過程：
1.剛開始學jsp，出現下圖這種問題，

因安裝的jdk沒 servlet-api.jar,servlet.jar

就把工程jdk改成idea自帶的了

之後便出現上述問題……..

之後就試著把jdk改回，成功了，，但是還會提示cannot resolve method，
最後把idea的jar都包含進來了，完成。