How to Write and Read from application.yaml in a Spring Boot Application at Runtime

Описание: Learn how to dynamically write and read key-value pairs from an `application.yaml` file in your Spring Boot application during runtime. This guide covers step-by-step instructions with practical examples.
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How to Write and Read from application.yaml in a Spring Boot Application at Runtime

If you’ve been working with Spring Boot and YAML configurations, you might have come across the need to modify your application's configuration files on the fly. The ability to write to and read from application.yaml or application.properties at runtime can be quite beneficial, such as when you want to store user-specific settings or other dynamically generated data. In this guide, we will provide you with a clear and concise method to accomplish this using Java code within a Spring Boot application.

Understanding the Challenge

Many developers face the challenge of effectively managing application configurations that can change over time. The key aspects to consider include:

Dynamic Key-Value Pair: You might need to allow either dynamic entries or predefined keys that require runtime modification.

Accessibility: Once you've written new values in the YAML or properties file, you want to ensure those values can be accessed across your application whenever needed.

Solution Overview

To achieve the above goals, we will utilize Spring Boot's @ ConfigurationProperties. This powerful feature allows us to bind the properties from the configuration file to Java classes, making it easier to work with configuration values.

Step 1: Add Necessary Dependencies

To start, ensure you have the required dependencies in your pom.xml if you are using Maven. If you're using Gradle, you can add the equivalent dependencies.

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Step 2: Create a Configuration Class

Create a configuration class to bind your properties. For example:

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In this example, properties prefixed with custom will be bound to the myValue field.

Step 3: Writing to the YAML File

To write new values into the application.yaml file, you can create a service that handles file writing. Here is a simplified version of how you might do that:

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Step 4: Reading from the YAML File

Reading from the YAML file is straightforward, especially since it’s tied to the binding class you created earlier. You can access the value dynamically as shown below:

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Step 5: Refreshing Context (Optional)

Sometimes, you'll need to refresh the application context to reflect the changes made. You can achieve this using @ RefreshScope or by leveraging Spring Cloud Config for more advanced scenarios.

Conclusion

In this guide, we’ve shown you how to write and read from application.yaml in a Spring Boot application at runtime using @ ConfigurationProperties. By using these steps, you can dynamically manage configuration values tailored to your application needs.

If you have additional questions or need further assistance, feel free to drop your thoughts in the comments below!