How to Fix Null Repository Issue with @ Autowired in Spring Boot

Discover how to resolve the `Null` repository problem when using @ Autowired in Spring Boot by correctly initializing your utility classes.
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Understanding the Null Repository Issue in Spring Boot

In the world of Spring Boot development, you might find yourself in a puzzling situation where the @ Autowired feature doesn't behave as you would expect. One common issue developers encounter is dealing with a null repository when attempting to retrieve a user from the database. This guide tackles a specific scenario: you have a controller that can successfully obtain a user, but when you move that functionality into a utility class, the userRepository turns out to be null. Let's delve into this issue, understand why it occurs, and explore the solution step-by-step.

The Problem Description

In your original controller, the code works perfectly with @ Autowired, allowing you to fetch a user like this:

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

However, after moving the code to a Utilities class and attempting to instantiate the class using the new keyword, you encounter this error:

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

You might wonder: Why is the userRepository null if it uses the @ Autowired annotation just like in the original implementation?

Why Does @ Autowired Fail in Utility Classes?

The key issue here lies in how Spring manages its beans. When you use the new keyword to create an instance of Utilities, this instance is not managed by the Spring container. As a result, Spring cannot inject the userRepository as a dependency, leading to a null reference.

Spring Dependency Injection

Spring Context: Only beans managed by the Spring application context can have their dependencies injected via @ Autowired.

Instantiation: When you manually instantiate a class, as in Utilities utilities = new Utilities();, Spring does not track this object. Thus, any @ Autowired fields in it will remain unset.

The Solution: Use Spring to Manage Your Utility Class

To solve this issue, you need to let Spring handle the creation of your Utilities class so that it can properly inject the required dependencies. Follow these steps to correct the issue:

Step 1: Annotate the Utilities Class

You need to tell Spring that your Utilities class is a managed component. To do this, add the @ Component annotation (or alternatively, you can use @ Service).

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

Step 2: Autowire the Utilities Class in Your Controller

Next, you need to autowire the Utilities class in your controller, allowing Spring to inject the instance automatically.

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

Conclusion

By ensuring that the Utilities class is properly recognized and managed by the Spring container, you can leverage the powerful features of dependency injection effectively. The key takeaway is that you must allow Spring to instantiate your classes for @ Autowired to work correctly. This adjustment will help you avoid the null repository issue and allow your application to function smoothly.

Now you're ready to tackle this common pitfall in Spring Boot development with confidence!