routing-data-source | using Spring RoutingDataSource and custom annotations | Build Tool library

I'm getting an issue with Spring framework while I try to connect to 2 identical databases (with same tables) and then choose one of them to make requests. I'm using for this, 3 config files DbConfig, AbstractRoutingDataSource and an application.properties file. I'm currently not getting any ERRORS, while starting my application, but any time I use my restful webservice I get empty data, check the controller file below.

NOTE: I've followed all these links and still no results:

1. Baeldung AbstractRoutingDataSource guide
2. Alexander guide
3. Dynamic DataSource Routing on Spring website

I'm working on Spring boot v2.0.5.

NOTE: please do NOT answer me if you don't have any ideas about AbstractRoutingDataSource class and how it works.

In our application, we have a common database called central and every customer will have their own database with exactly the same set of tables. Each customer's database might be hosted on our own server or the customer's server based on the requirement of the customer organization.

To handle this multi-tenant requirement, we're extending the AbstractRoutingDataSource from Spring JPA and overriding the determineTargetDataSource() method to create a new DataSource and establish a new connection on the fly based on the incoming customerCode. We also use a simple DatabaseContextHolder class to store the current datasource context in a ThreadLocal variable. Our solution is similar to what is describe in this article.

Let's say in a single request, we'll need to update some data in both the central database and the customer's database as following.