Resetting database url string dynamically - spring-boot

Question

I am working on a spring boot app that has two databases lets call them A and B. Database A has the list of clients (registered users) and database info and severs as the #Primary database, and Database B holds all client specific data. Database B is configured dynamically based on the user that logs in. The First page of the app shows a list of clients from which a user selects a list item, the db url string is passed to the bean configuring the datasource, and then the user is prompted to login. How can you achieve this in spring boot?
I tried the AbstractRoutingDataSource but that requires all the databases to be hard coded (or known before hand), but since new databse is created ever time a new user registers, it is possible that there will be new databases will be left out. So the database needs to be set at run time from a dynamic list, hence the need for a separate database A. How does one intialize a database from a list and make it available for the user until the user logs out?
This is the code for the primary database configuration (Database A):
#Configuration
#EnableJpaRepositories(
basePackages = "com.domu.nyomba",
entityManagerFactoryRef = "nyombaEntityManager",
transactionManagerRef = "nyombaTransactionManager")
public class NyombaDBConfig {
#Primary
#Bean
#ConfigurationProperties(prefix="spring.datasource")
public DataSource nyombaDataSource() {
return DataSourceBuilder.create().build();
}
#Bean
#Primary
public LocalContainerEntityManagerFactoryBean nyombaEntityManager() {
LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
em.setDataSource(nyombaDataSource());
em.setPackagesToScan(new String[] { "com.domu.nyomba"});
HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
em.setJpaVendorAdapter(vendorAdapter);
Map<String, Object> properties = new HashMap<>();
em.setJpaPropertyMap(properties);
return em;
}
#Bean
#Primary
public PlatformTransactionManager nyombaTransactionManager() {
JpaTransactionManager transactionManager = new JpaTransactionManager();
transactionManager.setEntityManagerFactory(nyombaEntityManager().getObject());
return transactionManager;
}
}
This is the code for the client configuration (Database B):
#Configuration
#EnableJpaRepositories(
basePackages = "com.domu.activist",
entityManagerFactoryRef = "activistEntityManager",
transactionManagerRef = "activistTransactionManager"
)
public class ActivistDBConfig {
#Bean
public DataSource activistDataSource() {
return DataSourceBuilder.create().url("put the db url here as a variable/parameter")
.password("root")
.username("root")
.build();
}
#Bean
public LocalContainerEntityManagerFactoryBean activistEntityManager() {
LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
em.setDataSource(activistDataSource());
em.setPackagesToScan(new String[] { "com.domu.activist" });
HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
em.setJpaVendorAdapter(vendorAdapter);
Map<String, Object> properties = new HashMap<>();
em.setJpaPropertyMap(properties);
return em;
}
#Bean
public PlatformTransactionManager activistTransactionManager() {
JpaTransactionManager transactionManager = new JpaTransactionManager();
transactionManager.setEntityManagerFactory(activistEntityManager().getObject());
return transactionManager;
}
}
I need assistance with how to pass a variable that has the value of the database URL to the activist DataSource above, and how to initialize the datasource, point it to the right database and make it available unit the user logs out.
Please use an example to explain.
Thanks. DMuts