[GWT] [ERROR] Hint: Check that your module inherits 'com.google.gwt.core.Core'

[Clint Yang]

Hi all,

I haven't done GWT development for a while and wanted to try again. I installed JDK 12 and Eclipse 2019-03. I installed GWT Eclipse Plugin (GWT 2.8.1). 

From Eclipse, I created a hello world project this way:

1. Click on 'New GWT Application Project'
2.  Project name: Gwt5, Package: com.foo, Use default SDK (GWT 2.8.1)
3. Click on 'GWT Compile Project'

I see this error:

Compiling module com.foo.Gwt5

   [ERROR] Hint: Check that your module inherits 'com.google.gwt.core.Core' either directly or indirectly (most often by inheriting module 'com.google.gwt.user.User')

I didn't change my gwt.xml.

Any suggestion?

[Craig Mitchell]

I don't believe GWT supports Java 12 yet.  I'd recommend just using Java 8.

And you might want to use the latest GWT version (2.8.2).

[Christian Nzhie]

Hello here.
I would like to react for this threat. Would at this time (2022) gwt supports java 12?
For I am experiencing the error mentioned above.
Thanks in advance.

[Michael Conrad]

We are using JDK 17 here at the office for builds without any issue. (Gradle setup here).

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[Thomas Broyer]

See https://www.gwtproject.org/release-notes.html#Release_Notes_2_10_0

GWT *runs* on JDKs from 8 to 17; you can however only compile Java 11 –at most– source files (depending on -sourceLevel).

When facing that kind of error, make sure you run with -failOnError (or its older name: -strict), and possibly use a more verbose -logLevel.