As a Java developer, you are probably familiar with the Spring Framework and its capabilities. Spring Boot, in particular, has gained a lot of popularity in recent years due to its ability to simplify the development process and make it easier to create stand-alone, production-grade applications. One of the features that Spring Boot provides is the ability to use external configuration files. However, what happens when you need to use multiple external configuration files in a Spring Boot application? In this blog post, we will explore different ways to use multiple external configuration files in a Spring Boot application.
Why Use External Configuration Files in Spring Boot
Before diving into the details of how to use multiple external configuration files, it’s important to understand why you might want to use external configuration files in the first place.
First, external configuration files allow you to separate your application’s configuration from its code. This can be especially useful when deploying your application to different environments, such as development, staging, and production. You can have a different set of configuration properties for each environment, and easily switch between them by modifying the external configuration files.
Second, external configuration files can also be useful for managing sensitive information, such as database credentials or API keys. By keeping this information in external configuration files, you can keep it out of your codebase and avoid accidentally committing it to source control.
Finally, external configuration files can be easily managed by non-developers, allowing them to make changes to the application’s configuration without having to modify the code.
Using the spring.config.name and spring.config.location Properties
The first way to use multiple external configuration files in a Spring Boot application is by using the spring.config.name and spring.config.location properties in the application.properties file. The spring.config.name property specifies the name of the configuration file, while the spring.config.location property specifies the location of the configuration file. By default, Spring Boot looks for a configuration file named application.properties in the classpath. However, you can specify a different name and location by setting the spring.config.name and spring.config.location properties.
For example, let’s say you have two configuration files named application-dev.properties and application-prod.properties. To use these configuration files, you would set the spring.config.name property to “application” and the spring.config.location property to “file:/etc/config/”. Then, you would run the application with the appropriate profile by using the following command:
java -jar myapp.jar --spring.profiles.active=dev
This would tell Spring Boot to use the application-dev.properties configuration file. Similarly, you can use the production profile to use the application-prod.properties configuration file.
Using the spring.config.additional-location Property
Another way to use multiple external configuration files in a Spring Boot application is by using the spring.config.additional-location property. This property allows you to specify additional locations where Spring Boot should look for configuration files. This can be useful if you have configuration files that are specific to a particular environment, such as development or production.
For example, let’s say you have two configuration files named application-dev.properties and application-prod.properties. To use these configuration files, you would set the spring.config.additional-location property to “file:/etc/config/dev” and “file:/etc/config/prod” respectively. Then, you would run the application with the appropriate profile by using the following command:
java -jar myapp.jar --spring.profiles.active=dev
This would tell Spring Boot to use the configuration files located in the /etc/config/dev directory. Similarly, you can use the production profile to use the configuration files located in the /etc/config/prod directory.
Using @PropertySource annotation
The @PropertySource annotation is a way to specify the location of external property files in a Spring Boot application. This annotation can be used to load multiple external configuration files, giving you more control over which properties get loaded and when.
To use the @PropertySource annotation, you’ll need to create a configuration class, such as ApplicationConfig, and add the @Configuration annotation to it. Then, you can add the @PropertySource annotation to the configuration class, specifying the location and name of the external configuration files you want to load.
For example, let’s say you have two configuration files named application-dev.properties and application-prod.properties. To use these configuration files, you would add the @PropertySource annotation to the ApplicationConfig class, specifying the location of the external configuration files:
@Configuration
@PropertySource({"file:/etc/config/dev/application-dev.properties",
"file:/etc/config/prod/application-prod.properties"})
It’s important to note that the order in which the external configuration files are specified in the @PropertySource annotation is important. Properties defined in later files will take precedence over properties defined in earlier files. This can be useful if you have a set of common properties that you want to define in one file, and then override them in environment-specific files.