Spring YAML Configuration

落日映苍穹つ 2024-03-25 20:48 45阅读 0赞

One of the ways of configuring Spring applications is using `YAML configuration files`.

## Spring YAML File ##

1、Spring profiles help enable `Spring Applications` to define `different properties` for `different environments`.  
2、`application.yml` relative path is `/myApplication/src/main/resources/application.yml`

Let’s take a look at `a simple YAML file` that contains two profiles. separating by `three dashes`.

# 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.com

The properties defined in the profile-specific documents won’t be loaded unless we explicitly indicate it.

## Binding YAML to a Config 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:  
1、***`@Configuration`*** – `marks the class as a source of bean definitions`  
2、***`@EnableConfigurationProperties`*** – `enable` ***`@ConfigurationProperties`*** annotated beans in the Spring application  
3、***`@ConfigurationProperties`*** – `binds and validates the external configurations to a configuration class`

## Accessing the YAML Properties ##

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.

spring.profiles.active=prod

@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());
        }
    }
    
    using environment: production
    name: prod-YAML
    enabled: true
    servers: [www.abc.com, www.xyz.com]

## YAML Property Overriding ##

In Spring Boot, YAML files can be overridden by other YAML properties files.

`in order of highest precedence first`:  
1、Profiles’ properties placed outside the packaged jar  
2、Profiles’ properties packaged inside the packaged jar  
3、Application properties placed outside the packaged jar  
4、Application properties packaged inside the packaged jar

**参考：[Spring YAML Configuration][]**

[Spring YAML Configuration]: https://www.baeldung.com/spring-yaml