You can verify the REST Service content by using the special validation service before saving.

To do that, simply click on the toolbar;

Or, go to Run --> Validate from the top menu. In case of no errors in the service, there will be a message in the Output tab:

[INFO]
rennes.groovy validated successfully".

Otherwise, there will be an error message displayed in the Output tab:

[ERROR] rennes.groovy validation failed. Error (400: Bad Request)
Unexpected error. Error occurs when parse stream, compiler error:
startup failed, rennes.groovy: 4: unable to resolve class javax.ws.rs.Path1
@ line 4, column 1.rennes.groovy: 8: unable to resolve classpath , unable to find class for annotation
@ line 8, column 1.rennes.groovy: 11: unable to resolve classpath , unable to find class for annotation
@ line 11, column 3.
3 errors

You can click the error message in the Output pane to go to the line containing the error in the REST Service file. In case the file has been closed, eXo IDE will automatically open it. Make sure that you do not delete or rename this file after the error message has been displayed in the Outline pane.