Play framework tutorial: Cannot resolve symbol 

问题:

I followed a tutorial here and although I got the entire tutorial working just fine, one of the classes in my IntelliJ project is marked with "red warnings". I cannot figure out what the problem is here? The project works but it shows these warnings? Any ideas on what this is and how to fix it? In the tutorial, about 3.5 minutes into it, the red marks magically disappear and the video presenter doesn't explain it.

回答1:

The Play 2.0 support plugin is only available in the IntelliJ IDEA Ultimate edition.

回答2:

This process worked for me:

1. go into [File -> Project Structure -> Modules -> [YourAppModule] -> Sources Tab]
2. navigate to the "target/scala-[version]/src_managed" directory (panel on the right).
3. Right click the "main" directory and flag it as a source folder.
4. Right click "controllers" and "views" and remove the "sources" flag (you should see the controllers and views folder become package directories).
5. Apply -> OK -> recompile.

from https://github.com/playframework/playframework/issues/1784#issuecomment-26345523

回答3:

Views / templates are not classes, which is why IDE cannot recognize them. IDE should be configured to look for the compiled version of the views. This click will fix your issue

回答4:

I managed to make it work on IDEA Community 14 by solely cleaning IDEA cache (File -> Invalidate Caches / Restart)

回答5:

The routes file and the views are compiled only when the project is first loaded in the browser. Till then, IntelliJ shows the error as it cannot find those classes. But the errors magically dissppear when you run the application and load it into browser.

You can verify this in the play console. After you do a play run , and load the url localhost:9000 in the browser, you can see compilation messages in the play console saying

...compiling 22 scala sources....

回答6:

Go to the Run configuration for your Play project and remove the 'Make' step from the "Before Launch" section. Then, IntelliJ would simply run the Play project without attempting to compile, and the views will get compiled automatically.

Until the views are compiled, IntelliJ doesn't know they exist, and can't make the project itself. Clearly this is a problem with IntelliJ's plugin, but since you're already relying on Play to do your compiling dynamically, this workaround doesn't hurt the workflow too much.

回答7:

1. Open "Project" sidebar
2. Go to target/scala-<version>/src_managed
3. Right-click the src_managed, "Mark Directory As"/"Generated Source Root"
4. Subdirectories of src_managed are from a strange reason marked as source roots. You can disable it.
5. Enjoy.

Note that javascript routes seem to be still ignored from a strange reason, so this is not a perfect solution. Nevertheless, it is better than nothing.