More flexible code: SAS

The warrant to our local hello server, the hello-local-warrant.xml, carries its own descriptor which carries its own codebase. This is a disadvantage for two reasons.

First, and most obviously, the descriptor's codebase contains encoded JARs which makes it huge. This is even more obvious for the netlet descriptor of the client which contains libjtrix.jar which is very large. And this isn't even a large application.

Second, the client netlet may carry the warrant for some time before it uses it, and during this time the code for the service may get out of date. In fact in general a service will always want to deliver the latest code, regardless of how old is the client's right to use that service--i.e. regardless of how old their warrant is.

The solution to both these problems is a SAS.

First, JAR files can be uploaded into a Web server and referenced by URL. jtrixmaker contains options to reference JARs by URL and not have them embedded in a netlet descriptor. See the options -jar-bases, -jar-urls and -embedded in Appendix . A SAS acts as a simple Web server, allowing JARs to be uploaded and referenced by URL.

Second, SAS also allows netlet descriptors to be uploaded and referenced by URL, so these do not have to be carried in the warrant, but only referenced. The downloaded hello-warrant.xml contains an example of these so-called bind servers, because the URLs say where the service can be bound from. See the option -bind-urls of jtrixmaker in Appendix .

This latter feature of a SAS, offering netlet descriptors, is its main feature. It's a bit more than just an HTTP download because the SAS needs to send a bit of header information with the netlet descriptor.

Once we have our netlet descriptors and JARs uploaded into a SAS it also helps us update them as necessary, as well as sending selected appropriate netlet descriptors to different clients, depending on their needs.

Thus a fully-fledged Jtrix service will make use of a SAS, just to help it manage its distribution more easily. Again, Beatrix aids in this a lot.