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Spring YAML Configuration
Last updated: March 27, 2025
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.
And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.
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Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
1. Overview
One of the ways of configuring Spring applications is using YAML configuration files.
In this quick tutorial, we’ll configure different profiles for a simple Spring Boot application using YAML.
Further reading:
A Quick Guide to Spring @Value
Learn to use the Spring @Value annotation to configure fields from property files, system properties, etc.
Using Spring @Value With Defaults
A quick and practical guide to setting default values when using the @Value annotation in Spring.
How to Inject a Property Value Into a Class Not Managed by Spring?
Learn how to initialize properties values in Java classes without the direct use of Spring's injection mechanism.
2. Spring YAML File
Spring profiles help enable Spring Applications to define different properties for different environments.
Let’s take a look at a simple YAML file that contains two profiles. The three dashes separating the two profiles indicate the start of a new document, so all the profiles can be described in the same YAML file.
The relative path of the application.yml file is /myApplication/src/main/resources/application.yml:
spring:
config:
activate:
on-profile: test
name: test-YAML
environment: testing
enabled: false
servers:
- www.abc.test.com
- www.xyz.test.com
---
spring:
config:
activate:
on-profile: prod
name: prod-YAML
environment: production
enabled: true
servers:
- www.abc.com
- www.xyz.comNote that this setup doesn’t imply that any of these profiles will be active when we start our application. The properties defined in the profile-specific documents won’t be loaded unless we explicitly indicate it; by default, the only active profile will be ‘default.‘
3. Binding YAML to a Config Class
To load a set of related properties from a properties file, we will create a bean class:
@Configuration
@EnableConfigurationProperties
@ConfigurationProperties
public class YAMLConfig {
private String name;
private String environment;
private boolean enabled;
private List<String> servers = new ArrayList<>();
// standard getters and setters
}The annotations used here are:
- @Configuration – this marks the class as a source of bean definitions
- @ConfigurationProperties – this binds and validates the external configurations to a configuration class
- @EnableConfigurationProperties – this annotation is used to enable @ConfigurationProperties annotated beans in the Spring application
4. Accessing the YAML Properties
To access the YAML properties, we’ll create an object of the YAMLConfig class, and access the properties using that object.
In the properties file, we’ll set the spring.profiles.active environment variable to prod. If we don’t define this property, only the ‘default’ profile will be active.
The relative path for the properties file is /myApplication/src/main/resources/application.properties:
spring.profiles.active=prodIn this example, we’ll display the properties using the CommandLineRunner:
@SpringBootApplication
public class MyApplication implements CommandLineRunner {
@Autowired
private YAMLConfig myConfig;
public static void main(String[] args) {
SpringApplication app = new SpringApplication(MyApplication.class);
app.run();
}
public void run(String... args) throws Exception {
System.out.println("using environment: " + myConfig.getEnvironment());
System.out.println("name: " + myConfig.getName());
System.out.println("enabled:" + myConfig.isEnabled());
System.out.println("servers: " + myConfig.getServers());
}
}The output on the command line:
using environment: production
name: prod-YAML
enabled: true
servers: [www.abc.com, www.xyz.com]5. YAML Property Overriding
In Spring Boot, YAML files can be overridden by other YAML properties files.
Prior to version 2.4.0, YAML properties were overridden by properties files in the following locations, in order of highest precedence first:
- Profiles’ properties placed outside the packaged jar
- Profiles’ properties packaged inside the packaged jar
- Application properties placed outside the packaged jar
- Application properties packaged inside the packaged jar
As of Spring Boot 2.4, external files always override packaged files, regardless of whether they’re profile-specific or not.
6. Conclusion
In this brief article, we learned how to configure properties in Spring Boot applications using YAML. We also discussed the property overriding rules followed by Spring Boot for YAML files.
The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
