When saving a ruby source file that resides in a project, eclim will update that source file in Eclipse and will report any validation errors found. Any errors will be placed in the current window's location list (:help location-list) and the corresponding lines in the source file will be marked via Vim's :sign functionality with '>>' markers in the left margin.
Automatic validation of ruby source files can be disabled via the g:EclimRubyValidate variable (described below). If you choose to disable automatic validation, you can still use the :Validate command to manually validate the current file.
g:EclimRubyValidate (Default: 1) - If set to 0, disables source code validation.
When enabled, syntastic is disabled so that eclim and syntastic don't step on each other. If you'd like to use syntastic over eclim for validation, then simply disable eclim's validation.
If you'd like to disable eclim's source code validation for all languages, eclim provides a global variable for that as well:
let g:EclimFileTypeValidate = 0
g:EclimValidateSortResults (Default: 'occurrence') - If set to 'severity', the validation results will be sorted by severity (errors > warnings > info > etc.)