GAE程序导入错误：Your project must be configured to use a JDK in order to use JSPs

导入一个以前写的Google App Engine程序，会提示你配置JDK的错误

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原因是用eclipse开发GAE的时候，默认的是JRE System Library，将JDK include进来就OK了。

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My JSPs aren't working, and there's an error that says "Your Web Application Project must be configured to use a JDK in order to use JSPs." What happened?

Both the local App Engine server and the deployment process need to run javac in order to compile your JSPs. If your project isn't set to use a JDK ("Java Development Kit", which includes javac), then the JSPs can't be compiled.

Go to Preferences > Java > Installed JREs and make sure that you have a JDK installed -- if you don't, you can easily download one. Now right-click on your project and choose Properties > Java Build Path > Libraries and make sure that your project is using this JDK.