Hello,
If you're generating sources with Maven, you can use Maven properties (which you can define in environment specific profiles or external properties files) for the JDBC conneciton parameters.
Another option is to use programmatic code generation configuration [1], which would give you full control over the configuration per environment.
There was a feature request to support system properties for these things [2]. At the time, I had rejected the feature request, because I feel these properties won't stop at JDBC connection parameters, and there are better, more robust solutions than these properties.
I hope this helps,
Lukas