Springboot all possible ways to read props from Configuration file.

Springboot YML/ Properties file

Various properties can be specified inside your application.properties file or inside your application.yml file, the following ways to reading properties from YML or Properties file.

• Reading a single property
• Read bunch of properties then use can use @ConfigurationProperties.
• Read entire YML/Property file

Visit following URL and here you can find more properties:
https://docs.spring.io/spring-boot/docs/1.1.6.RELEASE/reference/html/common-application-properties.html
https://docs.spring.io/spring-boot/docs/current/reference/html/application-properties.html

In my case i’m using YML file

voyagers:
  enabled: true
  basePath: "/"
  mapping: "/voyager"
  endpoint: "/graphql"

Reading a single property

You can use @Value(“${<property-name>}) annotation

@Value("${voyagers.enabled}")
private String voyagerEnable;

Read bunch of properties

If you want to read bunch of properties then there are two ways:

• @ConfigurationProperty(prefix) with @EnableConfigurationProperties annoation
• @ConfigurationProperty(prefix) with @Components

@ConfigurationProperty(prefix) with @EnableConfigurationProperties(<property class>) annoation

Let’s register our configuration bean using @EnableConfigurationProperties:

@EnableConfigurationProperties – Creates a binding between a configuration entity class and Spring configuration stereotype so that after injection within a service properties can be retrieved easily.

@ConfigurationProperties(prefix = "voyagers")
public class AppProperties {
private Boolean enabled;    private String basePath;
    private String mapping;
    private String endpoint;
}@Service
public class AppPropertiesDemo {
    @Autowired
    private AppProperties appProperties;

    void checkProp(){
        System.out.println("Reading bunch of app properties =>" + appProperties);
    }
}

Main class:
@SpringBootApplication
@EnableConfigurationProperties(AppProperties.class)
public class GraphQlApplication implements ApplicationRunner {
	@Autowired
	private AppPropertiesDemo appPropertiesDemo;
	public static void main(String[] args) {
		SpringApplication.run(GraphQlApplication.class, args);
	}

	@Override
	public void run(ApplicationArguments args) throws Exception {
		appPropertiesDemo.checkProp();
	}
}

@ConfigurationProperties – Used to bind a class with an externalized property file. Very powerful and must be used to separate out bean classes with configuration entity class.

@ConfigurationProperties(prefix = "voyagers")
@Component
public class AppProperties {
    private Boolean enabled;
    private String basePath;
    private String mapping;
    private String endpoint;
}

We can autowire this property class as like that:
@Autowired
private AppProperties appProperties;

Read entire yml or property file

Spring Boot initializes its environment, it uses properties files, YAML files, environment variables, and command-line arguments to externalize the configuration.

This section i will discuss how to read the application property but it’s not a recommended approach, instead of that we use @Value annotation..

For that we can autowire spring framework class Environment bean. The @SpringBootApplication annotation enables auto-configuration and component scanning.

@Autowired
private Environment env;

log.info("Reading single property"+ environment.getProperty("voyagers.enabled"));

In this blog we have covered various way (Single | Multiple Properties | Entire Properties) to read properties of spring/spring-boot configuration file.