Best way to initialize a variable and use it in 2 service classes in java , as thread safe

Question

This is first class:

@Service
public class ServiceA{

@Autowired
ServiceB serviceB;

String neededString;

public void methodSome(){
//uses neededString
}

}

This is second

@Service
public class ServiceB{

String neededString;

public void methodSome(){
//uses neededString
}
}

and i need to get the variable from another service:

neededString = thirdServiceToReturn();

Both classes need that neededString variable to do their own methods. I can get from 3. service in the method seperately or i can get with PostConstruct for each class.

But i want to get from a common place for both classes. Maybe from 2. class . I can try static but it wont be thread safe i guess.

The variable wont change for months maybe. It takes some values and returns from database. After some deploy, it can change so, it should get new one at some point.

I use Spring Boot also. What do you suggest?

Maybe a Constant class with @Bean and do the initializing there and then Autowired to second class? Like that: Is there any way to pass @Autowired variable to some other class in a Spring Boot application?

The variable will change in future. It is reading from database, which is derived with @cached so it will read from cache until the application is restarted or is deployed. Variable needs to be parametric, not hardcoded.

Static variable is not thread safe. I want to reach the solution. Thread safe.

Answer 1

This is first class:

@Service
public class ServiceA{

@Autowired
ServiceB serviceB;

public static String neededString;

@PostConstruct
public void setupNeededString() {
    neededString = “”;
}

public void methodSome(){
//uses neededString
}

}

This is second

@Service
public class ServiceB{



public void methodSome(){
//uses ServiceA.neededString
}
}