Reading application.properties in Spring Boot

Read application.properties Using the Environment

1) Use the @Autowired annotation to inject the Environment object into your Rest Controller or Service class, like so:

1. @Autowired
2. private Environment env;

2) User getProperty(String key) method to get a value for a specific property. Like this:

1. String keyValue = env.getProperty(key);

Let’s assume I have these properties in my application.properties file:

1. app.title=Learning Spring Boot
2. app.description=Working with properties file

and I need to create a Web Service endpoint that accepts property key name as request parameter and returns property value.

1. 
   String title = env.getProperty("app.title");

1. 
   String description = env.getProperty("app.description");

Reading Properties with @Value Annotation

To read the value of app.title property, annotate the class field with @Value annotation like so:

1. @Value("${app.title}")
2. private String appTitle;

Reading Application Properties with @ConfigurationProperties

For example, let’s assume we have the same application.properties file:

1. app.title=Learning Spring Boot
2. app.description=Working with properties file

Because each of the property names starts with a prefix of app we will need to annotation our Java Bean with:

1. @ConfigurationProperties("app")

Here is an example of Java class annotated with @ConfigurationProperties annotation:

1. 
   
3. import org.springframework.boot.context.properties.ConfigurationProperties;
4. import org.springframework.stereotype.Component;
6. @Component
7. @ConfigurationProperties("app")
8. public class AppProperties {
10. private String title;
11. private String description;
12. 
    
13. //getters and setters
14. }

To use this class in Rest Controller or Service class we simply autowire it by using the @Autowired annotation.

2. @RestController
3. @RequestMapping("app")
4. public class AppController {
6. @Autowired
7. AppProperties myAppProperties;
9. //to get title
10. myAppProperties.getTitle();
11. //to get description
12. myAppProperties.getTitle();
14. }