Learn how to fix the issue of a missing autoconfigured bean in Spring Boot. Discover how to correctly set up your project dependencies and configurations to ensure proper bean loading.
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Resolving Bean Not Found Issues in Spring Boot with Autoconfigured Beans

When working on a Spring Boot application, you might encounter issues related to autoconfigured beans not being loaded properly in the application context. This can be particularly frustrating, especially when you are confident that everything is set up correctly. In this guide, we'll explore a common scenario involving autoconfigured beans and how to resolve these errors effectively.

The Problem

Suppose you have two projects: A and B. Project A contains an autoconfigured class, MyAutoConfig, defined in the spring.factories file. Within this configuration, you have defined a bean called Worker. Project B is using Project A as a dependency through Gradle with the following line:

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Everything appears to be in order since Project B starts without any issues. However, when you try to use the autowired Worker bean in the main class of Project B, which is annotated with -SpringBootConfiguration, you get an error message stating:

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This indicates that the Worker bean is not recognized by the Spring context in Project B.

The Solution

To resolve this issue, let’s break down the necessary steps needed to ensure that your autoconfigured bean is correctly loaded into the Spring context for Project B.

1. Understanding Configuration Annotations

The problem arises because the -SpringBootConfiguration annotation alone is insufficient for auto-configuration. You need the additional configuration provided by -EnableAutoConfiguration. Here’s an explanation of both annotations:

-SpringBootConfiguration: This annotation indicates that the class can be used by Spring to configure the application context but does not include auto-configuration functionality by itself.

-EnableAutoConfiguration: This annotation must be included to trigger the scanning of spring.factories files and to load the defined beans into the application context.

2. Modify Your Main Application Class

In the main class of Project B, you should ensure that you include -EnableAutoConfiguration. Alternatively, you can use the -SpringBootApplication annotation, which already combines both -SpringBootConfiguration and -EnableAutoConfiguration with some additional features. This is how your main class should look:

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3. Running Your Application

Once you have made these changes, try running Project B again. The Worker bean should now be injected properly, and you should no longer encounter the "expected at least 1 bean" error.

4. Additional Tips

If you continue to experience issues even after these modifications, consider the following tips:

Check Your Dependency: Ensure that Project A is correctly included as a dependency in Project B.

Verify Bean Definition: Double-check that the Worker bean is properly defined within your autoconfiguration class in Project A.

Use Logging: Enable debug logging for Spring to get more insight into what beans are being created and scanned during application startup.

By following these steps and keeping in mind the functionality of each Spring annotation, you can effectively resolve issues with autoconfigured beans and ensure that your Spring Boot application runs smoothly.

Conclusion

Encountering issues with autoconfigured beans in Spring Boot can be daunting, but understanding how auto-configuration works and properly implementing the necessary annotations can help streamline your application’s setup. Remember to always include -EnableAutoConfiguration or utilize -SpringBootApplication to ensure that yo