Spring : factory-method

Consider a java class containing no setter or constructor, but a static method to return its instance.

public class ClientService {    
    private static ClientService clientService = new ClientService();
    private ClientService() {}
    
    public static ClientService createInstance() {
        return clientService;
    }
}

So to creating this bean we use factory-method attribute on bean.

<bean id="clientService" class="ex2.ClientService" factory-method="createInstance" />

Case when factory-method as argument as well