Support different modules per interface simultaneously

[matthias-ronge]

Description

The Module Loader is currently programmed so that if there are several modules that offer an interface, it takes any of them. In principle, this can even change from one Tomcat start to the next.

The goal should be that several different modules for the same interface (e.g. several catalog modules) are operated in parallel and the user can select at a relevant point which module he or she wants to use.

TODO:

Part 1

• adjust Service Loader to enable multiple modules
• enable configuration to choose specific modules
• move module source code in separate repositories to keep them independent (start with API)

Part 2

• identify places, where user interaction is desired in frontend to select a specific module and implement selection

Estimated Costs and Complexity

Part 1

is a mid-ranged project with 6-7 PT

Part 2

is a mid-ranged project with 8-10 PT

[stefanCCS]

Sorry, but I do not really understand the purpose.
If this change would allow more/other features in the future, then please explain more detailed, what is about.
If it is "just" a software internal optimization, then please decide by your (dev team) own, if/when/how you would like to do this.

[matthias-ronge]

The reason Production was broken into modules is to allow for different modules. For example the Generator Interface: It should be possible to connect a URN generator as a module, and a PURL generator, and a process title generator, etc. Likewise, schema converter, if a new format is to be supported, a new schema converter is created for it. If two clients want to use two different data stores, two file management modules are used, one for example using the file system and the other using a repository. All of this presupposes that with several modules these can be used at the same time and that one that fits is not selected at random from several.

[stefanCCS]

Many thanks for sharing this details.
Now, at least I have an idea, and in general, this idea sounds very interesting.