How to recover architecture of a legacy system

I am trying to recover architecture of a legacy system.This is something new to me.Up to now I have read many research papers where most of the researchers have proposed frameworks and automated tools for this.But I have no idea how to choose the best from those frameworks or tools.All of the researched have some set of common steps like reverse engineering and forward engineering. Can someone help on this? What is the ground stage to begin the recovery architecture of a legacy system? What are the basic steps? Is there any guideline? Thanks

When converting a legacy system, you must keep in mind both the technology an the team. The changes you have to make will go to the core of the application, and if the dev team is not on board with the changes it will be a long slow migration.

The key to reworking a legacy system is dependency injection and service location. The first step is to install a dependency injection container and add a class to the container (the Logger is always a good first service).

Next step is to add a service locator. Constructor injection is the best approach for greenfield projects, but for legacy apps it's not possible at first. With the service locator you can access the injection container from anywhere, allowing service resolution where needed. With this in place you can sweep through and replace logger creation code with logger resolution code.

The logger replacement is an excellent example of how DI works, so demo this to the team. Make sure the team understands these concepts thoroughly! The rest of the process heavily depends on DI and service location.

The DI container breaks the tight coupling in legacy systems so you can break things apart. Start looking for seams where you can break the app into smaller pieces, which allows you to introduce unit testing. This will also lay the groundwork for a DDD migration, microservices, EDA, or whatever target architecture you have planned.