Singleton bean in Prototype bean in Spring Context

Question

Typically in Spring Context if a prototype bean is injected in a singleton bean, property of parent class overrides prototype bean scope. However what will happen if a singleton scope bean is injected in prototype bean scope. Still using get bean of the inner bean will return with new instance of inner bean?

gWombat gWombat · Accepted Answer · 2018-02-02T14:14:40

No, all instances of prototype bean will share the same instance of the singleton bean.
Example:

@Service
public class SingletonBean {
    private int id;
    private static int static_id = 0;

    public SingletonBean() {
        id = static_id++;
    }

    @Override
    public String toString() {
        return "SingletonBean [id=" + id + "]";
    }

}

@Service
@Scope("prototype")
public class PrototypeBean {

    @Autowired
    private SingletonBean singletonBean;
    private int id;

    private static int static_id = 0;

    public PrototypeBean() {
        id = static_id++;
    }

    @Override
    public String toString() {
        return "id=" + id + ", PrototypeBean [singletonBean=" + singletonBean + "]";
    }
}

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(DemoApplication.class, args);
        PrototypeBean beanA = context.getBean(PrototypeBean.class);
        PrototypeBean beanB = context.getBean(PrototypeBean.class);

        System.out.println(beanA); //id=0, PrototypeBean [singletonBean=SingletonBean [id=0]]
        System.out.println(beanB); //id=1, PrototypeBean [singletonBean=SingletonBean [id=0]]
    }
}

</code>

Singleton bean in Prototype bean in Spring Context

2 Answers