Why is `@RefreshScope` used in Java Spring?

Answered on : 2024-06-19

Sources

Introduction to @RefreshScope Annotation | by Eray Araz

medium.com

java - @RefreshScope in Configuration class

stackoverflow.com

Application Context Services

cloud.spring.io

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The `@RefreshScope` annotation in Java Spring, particularly in the context of Spring Boot applications, serves a crucial role in enabling dynamic reloading of configuration properties without needing a full application restart. Here's a breakdown of its purpose and functionality:

1. **Dynamic Configuration Updates**: When a Spring Boot application is configured as a client to a Spring Cloud Config Server, it fetches its configuration from this server at startup. The `@RefreshScope` annotation allows the application to re-fetch updated configuration values from the server without restarting the entire application[1].

2. **Scoped Bean Refresh**: When a bean is annotated with `@RefreshScope`, Spring manages it in such a way that changes to its properties (typically stored in the configuration server) trigger a refresh of the bean itself. This means that any updates made to the configuration properties will reflect in the bean instance, ensuring that the application adapts to new settings or configurations in real-time[2].

3. **Usage in Configuration Classes**: Placing `@RefreshScope` on a configuration class ensures that changes to the configuration properties are reflected in the instance fields of that class. However, it's important to note that this does not automatically refresh beans created by the configuration class; you need to manage bean refresh manually in such cases[2].

4. **Refreshing All Beans**: Spring also provides a `RefreshScope` bean within the application context, offering a `refreshAll()` method. This method clears the target cache and refreshes all beans annotated with `@RefreshScope`, ensuring that the entire application context can be dynamically updated without restarting the application[3].

5. **Best Practices**: While `@RefreshScope` is powerful for managing dynamic configuration updates, it's advised not to use it directly within controllers due to potential issues with maintaining state and ensuring predictable behavior. Instead, it's recommended to use it with beans that handle configuration properties and business logic separately[7].

In summary, `@RefreshScope` in Java Spring is essential for applications that require real-time updates to their configuration settings without downtime. It facilitates dynamic reloading of beans and configuration properties, making Spring Boot applications more adaptable and responsive to changing environments or operational requirements.