Scope of RestController and Controller in Spring - spring

Question

What should be the scope of Controller and RestController in a Spring application? The default behavior if being Singleton. But will not having single bean cross over the request/responses from multiple clients, as our Controller will call some other bean (say #Service) which handles user specific request (like fetching user details from a DB or from another REST/SOAP service).

Answer 1

You have two options here:
Option 1 - In your service classes, ensure that you do not save any request specific details in instance variables. Instead pass them around as method arguments.
Ex:
The below code will corrupt the value stored in userId if there are simultaneous requests.
#Service
public class SomeService {
String userId;
public void processRequest(String userId, String orderId) {
this.userId = userId;
// Some code
process(orderId);
}
public void process(String orderId) {
// code that uses orderId
}
}
While, the following code is safe.
#Service
public class SomeService {
private String userId;
public void processRequest(String userId, String orderId) {
// Some code
process(userId, orderId);
}
public void process(String userId, String orderId) {
// code that uses userId and orderId
}
}
Option 2:
You can save request specific data in request scoped beans and inject them in your singletons. Spring creates a proxy for the injected request scoped beans and proxies calls to the bean associated with the current request.
#RequestScoped
class UserInfo {
}
#Service
class UserService {
#Autowired
private UserInfo userInfo;
public void process(String orderId) {
// It is safe to invoke methods of userInfo here. The calls will be passed to the bean associated with the current request.
}
}