Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
1. Overview
Self-injection means that a Spring bean injects itself as a dependency. It uses the Spring container to obtain a reference to itself and then uses that reference to perform some operation.
In this short tutorial, we’ll see how to use self-injection in Spring.
2. Use Case for Self-Injection
The most common use case for self-injection is to bypass Spring AOP limitations when it’s necessary to apply an aspect to a method or class that is self-referencing.
Suppose we have a service class that performs some business logic and needs to call a method on itself as part of that logic:
@Service
public class MyService {
public void doSomething() {
// ...
doSomethingElse();
}
@Transactional
public void doSomethingElse() {
// ...
}
}However, when we run our application, we might notice that @Transactional isn’t applied. This is because the doSomething() method is calling doSomethingElse() directly, which bypasses the Spring proxy.
To work around this, we can use self-injection to get a reference to the Spring proxy and call the method through that proxy.
3. Self-Injection Using @Autowired
We can perform self-injection in Spring by using the @Autowired annotation on a field, constructor parameter, or setter method of a bean.
Here’s an example of using @Autowired with a field:
@Component
public class MyBean {
@Autowired
private MyBean self;
public void doSomething() {
// use self reference here
}
}And with a constructor parameter:
@Component
public class MyBean {
private MyBean self;
@Autowired
public MyBean(MyBean self) {
this.self = self;
}
// ...
}4. Self-Injection Using ApplicationContextAware
Another way to perform self-injection is by implementing the ApplicationContextAware interface. This interface allows a bean to be aware of the Spring application context and obtain a reference to itself:
@Component
public class MyBean implements ApplicationContextAware {
private ApplicationContext context;
@Override
public void setApplicationContext(ApplicationContext context) throws BeansException {
this.context = context;
}
public void doSomething() {
MyBean self = context.getBean(MyBean.class);
// ...
}
}5. Disadvantages
When a bean injects itself, it can create confusion about the responsibilities of the bean and make it harder to trace the flow of data through the application.
Self-injection can also create a circular dependency. Starting with version 2.6, Spring Boot will raise an exception if our project has circular dependencies. There are some workarounds, of course.
6. Conclusion
In this quick article, we’ve learned several ways we can use self-injection in Spring and when to use it. We’ve also learned some of the disadvantages of self-injection in Spring.
