The code generation capabilities in Sparx Enterprise Architect (EA) are slick and very helpful if you get to that level of detail. The problem many people run into is that not all the datatypes are set for their language. Like nearly everything in EA, this is configurable.
Select Config - > Settings -> Code Engineering Datatypes... from the ribbon menu:
Then select your language (or add it if it doesn't exist):
Next, select "New" and fill in the name and optionally the length then press "Save".
Now the next time you add/update attributes and operations in your models, you have the option to select your new data types.
If the type does not appear, make sure the element on which you are working has its language set to the language you selected when adding the type. I usually use Java and the default language for all my models is set to Java.