Need help figured out how to load nested list from yml in spring boot java app

Question

I have a yaml file setup like this:

system:
  locators:
  - first.com
    - 103
    - 105
  - second.com
    - 105

I want to load this as @autowired configuration that looks something like this:

@Autowired
List<Locator> locators;

I'm thinking that the Locator class would look something like this:

class Locator {
    String name;
    List<String> ports;
}

But I'm not sure how to put this all together. Any help is appreciated!

Answer 1

Firstly, I believe your yaml file structure is invalid. In your Locator class you have given names to the fields - you should do the same in your yaml file. In the end it should look like this:

system:
  locators:
  - name: first.com
    ports:
      - 103
      - 105
  - name: second.com
    ports:
      - 105

Secondly, you can leverage Spring Boot's rather advanced properties-to-bean auto mapping. As in every Spring Boot app, you need to annotate your main class with @SpringBootApplication. Then, you can create a class representing your properties structure:

@Configuration
@ConfigurationProperties(prefix = "system")
public class SystemProperties {

    private List<Locator> locators;

    public List<Locator> getLocators() {
        return locators;
    }

    public void setLocators(List<Locator> locators) {
        this.locators = locators;
    }

    public static class Locator {
        private String name;
        private List<String> ports;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public List<String> getPorts() {
            return ports;
        }

        public void setPorts(List<String> ports) {
            this.ports = ports;
        }

    }

}

Notice the @ConfigurationProperties annotation that defines the prefix which is the root of this classe's mapped configuration. It can of course be any node in a yaml tree of properties, not necessarily the main level as in your case.

For further reading I would suggest this blog post and the official documentation as there are more ppowerful abilities when it comes to property bean mapping.