How to Inject List of String Arrays in Spring from Properties File?

Learn how to easily inject a List of String arrays into your Spring application from a properties file using the Spring Expression Language.
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How to Inject List of String Arrays in Spring from Properties File?

In the world of Spring development, managing configuration through external properties files is essential for clean and maintainable code. However, what happens when you need to inject complex types, such as nested arrays? If you've ever wondered how to accomplish this, you’re in the right place! This guide will walk you through the process of injecting a List of String arrays in a Spring application using properties files, all while keeping it simple and straightforward.

Understanding the Problem

You might be trying to create a List of nested String arrays in your Spring Boot application. The challenge is to correctly format your properties so that Spring can appropriately interpret and inject these nested arrays. Essentially, you want to store structured data in the properties file and retrieve it as a List of String arrays easily.

Solution Overview

Fortunately, Spring makes this process manageable through the use of Spring Expression Language (SpEL). By defining your properties in a specific format and leveraging SpEL, you can achieve your goal. Here’s how to do it step by step.

Step 1: Define Your Properties

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

Use a semicolon (;) to separate different arrays.

Use a comma (,) to separate items within the same array.

Step 2: Injecting the Properties

Next, you will need to inject these properties into your Spring application class. Here's how to create a simple application that reads the injected properties:

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

Explanation of the Code

-Value Annotation: Here, we use the -Value annotation to inject the properties. The SpEL expression '${LIST_OF_NESTED_ARRAYS}'.split(';') effectively splits the properties string into a List of String arrays.

Logging the Output: The run method logs each array to the console, allowing you to verify that the properties were injected correctly.

Step 3: Executing the Application

Once you have the code set up, run your Spring Boot application, and check your log output. If everything is configured correctly, you should see output that looks like this:

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

This confirms that your List of String arrays has been successfully injected and processed by Spring.

Conclusion

Injecting a List of String arrays from a properties file in a Spring application might seem complex, but with the right approach using Spring Expression Language, it can be accomplished with ease. Just remember to properly format your properties and use the -Value annotation correctly. This technique not only enhances your application's configuration management but also increases its maintainability and readability.

If you found this guide helpful, feel free to share it with fellow developers who might be tackling similar issues! Happy coding!