Why is Spring’s ApplicationContext.getBean considered bad?

by

I mentioned this in a comment on the other question, but the whole idea of Inversion of Control is to have none of your classes know or care how they get the objects they depend on. This makes it easy to change what type of implementation of a given dependency you use at any time. It also makes the classes easy to test, as you can provide mock implementations of dependencies. Finally, it makes the classes simpler and more focused on their core responsibility.

Calling ApplicationContext.getBean() is not Inversion of Control! While it’s still easy to change what implemenation is configured for the given bean name, the class now relies directly on Spring to provide that dependency and can’t get it any other way. You can’t just make your own mock implementation in a test class and pass that to it yourself. This basically defeats Spring’s purpose as a dependency injection container.

Everywhere you want to say:

MyClass myClass = applicationContext.getBean("myClass");

you should instead, for example, declare a method:

public void setMyClass(MyClass myClass) {
   this.myClass = myClass;
}

And then in your configuration:

<bean id="myClass" class="MyClass">...</bean>

<bean id="myOtherClass" class="MyOtherClass">
   <property name="myClass" ref="myClass"/>
</bean>

Spring will then automatically inject myClass into myOtherClass.

Declare everything in this way, and at the root of it all have something like:

<bean id="myApplication" class="MyApplication">
   <property name="myCentralClass" ref="myCentralClass"/>
   <property name="myOtherCentralClass" ref="myOtherCentralClass"/>
</bean>

MyApplication is the most central class, and depends at least indirectly on every other service in your program. When bootstrapping, in your main method, you can call applicationContext.getBean("myApplication") but you should not need to call getBean() anywhere else!

More Related Contents:

  1. Spring @Transaction method call by the method within the same class, does not work?
  2. How to configure port for a Spring Boot application
  3. Spring AOP not working for method call inside another method
  4. Spring AOP vs AspectJ
  5. JsonMappingException: No suitable constructor found for type [simple type, class ]: can not instantiate from JSON object
  6. What is the difference between @Inject and @Autowired in Spring Framework? Which one to use under what condition?
  7. Spring Java Config: how do you create a prototype-scoped @Bean with runtime arguments?
  8. CORS allowed-origin restrictions aren’t causing the server to reject requests
  9. Spring RestTemplate GET with parameters
  10. Spring CrudRepository findByInventoryIds(List inventoryIdList) – equivalent to IN clause
  11. Spring Cache with collection of items/entities
  12. Howto get rid of ?
  13. Spring: Standard Logging aspect (interceptor)
  14. Spring WebSocket @SendToSession: send message to specific session
  15. In Spring MVC, how can I set the mime type header when using @ResponseBody
  16. request scoped beans in spring testing
  17. How to handle requests that includes forward slashes (/)?
  18. Manually call Spring Annotation Validation
  19. Spring: Make sure a particular bean gets initialized first
  20. How to exclude *AutoConfiguration classes in Spring Boot JUnit tests?
  21. Spring/Java error: namespace element ‘annotation-config’ … on JDK 1.5 and higher
  22. Spring forward with added parameters?
  23. Spring Security multiple url ruleset not working together
  24. Encoded password does not look like BCrypt
  25. How can I run a Spring Boot application on port 80
  26. Spring MVC 4: “application/json” Content Type is not being set correctly
  27. SpringBoot ComponentScan issue with multi-module project
  28. Autowired Repository is Null in Custom Constraint Validator
  29. Trigger 404 in Spring-MVC controller?
  30. Logging response body (HTML) from HttpServletResponse using Spring MVC HandlerInterceptorAdapter

Leave a Comment