How do I "alias" the execution of a .jar file as a global command?

Create a batch file with the following:

java -jar C:\Users\Jacob\swagger-codegen-cli.jar %*

The %* portion tells the batch script to pass all of the parameters it receives to the new command.

If there are no other executables in the same directory as the .jar file, you can safely save the batch file there as swagger-codegen.bat and then add it to your PATH variable.

If there are other executables in the same directory, make sure they don't conflict with any other commands that might be reachable through your PATH variable.

The DOSKEY command can create an alias in cmd:

doskey swagger-codegen=java -jar C:\Users\Jacob\swagger-codegen-cli.jar

If you need this to be defined whenever cmd starts, you can define it in an initialisation file.