At 10.7, the GeoEvent Manager user interface has an issue uploading .jar files greater than 100KB. We are aware of the problem and actively working on fixing the issue. This workaround applies to any custom component you would deploy to GeoEvent using a .jar file.
In the meantime, if you experience issues uploading .jar files via the GeoEvent Manager interface, you can deploy them directly by placing them into the GeoEvent's Deploy directory (see below). You should do this while the GeoEvent service is running (do NOT stop the service).
<GeoEvent Install Location>\GeoEvent\deploy\
On a windows machine, the default location would be the following:
Once you copy the .jar file into this directory, you can check GeoEvent Manager to verify that the component was imported correctly (go to Site > Components > Transports | Adapters | Processors).