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Facing issues with your Spring Boot application startup due to `BeanCurrentlyInCreationException`? Learn how to resolve circular references in your security configuration.
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Resolving the BeanCurrentlyInCreationException in Spring Boot Application Startup

If you've recently encountered the dreaded BeanCurrentlyInCreationException while starting your Spring Boot application, specifically in the context of your securityConfig, you're not alone. This error typically indicates a circular dependency in your Spring beans, which can halt your application startup and require immediate attention. Let's break this down and explore ways to resolve the issue.

Understanding the Problem

The error you're facing is often due to a circular reference between the beans in your Spring configuration. In your case, it specifically involves the SecurityConfig class wherein:

You've defined several beans, including a PasswordEncoder.

The PasswordEncoder is utilized during the setup of the AuthenticationManagerBuilder.

Meanwhile, the SecurityConfig itself is also being instantiated at this time, leading to a conflict.

This interaction can create a loop, where Spring is unable to determine the order of dependency resolution, resulting in a failure to start your application.

Example of the Circular Reference

During the instantiation of SecurityConfig, the following happens:

SecurityConfig requires an instance of PasswordEncoder to be created.

However, PasswordEncoder is also linked back to components that require SecurityConfig, creating a circular pathway.

Solving the Issue

Simplest Solution: Static Bean Method

One of the easiest ways to break the circular dependency is by declaring the PasswordEncoder bean method as static. This adjustment instructs Spring to treat the method differently, breaking the circular reference.

Updated Code

Here’s how you can modify your SecurityConfig class:

[[See Video to Reveal this Text or Code Snippet]]

Why This Works

By declaring the passwordEncoder() method as static, you allow Spring to create the PasswordEncoder instance independently of the instance of the SecurityConfig class. This means the PasswordEncoder bean can be initialized without needing a reference to any instance variables, effectively breaking the circular dependency.

Additional Tips

While the above solution works for this specific case, here are a few general practices to avoid circular dependencies:

Careful Design of Beans: When designing beans, be mindful of their dependencies. Sometimes, breaking a larger bean into smaller components can help avoid circular references.

Use Constructor Injection: Opt for constructor injection rather than field injection; this often makes dependencies clearer and can reduce the risk of circular references.

Review Bean Scopes: Ensure that your beans are scoped appropriately (e.g., singleton, prototype), as this can affect their lifecycle and dependencies.

Conclusion

Diagnosing and solving issues like the BeanCurrentlyInCreationException can be daunting, especially when you're juggling multiple dependencies in a complex Spring Boot application. However, by implementing the simple change of marking your PasswordEncoder method as static, you've simplified your configuration and resolved the circular reference issue.

Now you can enjoy a smoother Spring Boot startup experience!