When you hit the command "mvn clean install", maven will clean the target folder during the build and place the latest jar after creating it again. So basically, this will update the jar with the new codebase.
Other than that, if you want to install only the OSGi bundle in the AEM instance, you can use the below command.
"mvn clean install -PautoInstallBundle".
Here, "-PautoInstallBundle" will install only the OSGi bundle in the AEM instance.
You need to deploy the OSGI bundle every time any code changes have been made.
otherwise, you can use Mockito framework to test your code with some dummy data before deploying it into the AEM. This will save your time to do the deployment every time. For this approach, you can create a test case and use some sample data for that.