Can I manually load @ConfigurationProperties without the Spring AppContext?

Question

Is there any way to load a class marked with @ConfigurationProperties without using a Spring Context directly? Basically I want to reuse all the smart logic tha

Answer 1

I had the same "issue". Here is how I solved it in SpringBoot version 1.3.xxx and 1.4.1.

Let's say we have the following yaml configuration file:

foo:
  apis:
      -
       name: Happy Api
       path: /happyApi.json?v=bar
      -
       name: Grumpy Api
       path: /grumpyApi.json?v=grrr

and we have the following ConfigurationProperties:

@ConfigurationProperties(prefix = "foo")
public class ApisProperties {
    private List apis = Lists.newArrayList();

    public ApisProperties() {
    }

    public List getApis() {
        return apis;
    }

    public static class ApiPath {
        private String name;
        private String path;

        public String getName() {
            return name;
        }

        public void setName(final String aName) {
            name = aName;
        }

        public String getPath() {
            return path;
        }

        public void setPath(final String aPath) {
            path = aPath;
        }
    }
} 

Then, to do the "magic" things of Spring Boot programmatically (e.g. loading some properties in a static method), you can do:

private static ApisProperties apiProperties() {
    try {
        ClassPathResource resource;
        resource = new ClassPathResource("/config/application.yml");

        YamlPropertiesFactoryBean factoryBean;
        factoryBean = new YamlPropertiesFactoryBean();
        factoryBean.setSingleton(true); // optional depends on your use-case
        factoryBean.setResources(resource);

        Properties properties;
        properties = factoryBean.getObject();

        MutablePropertySources propertySources;
        propertySources = new MutablePropertySources();
        propertySources.addLast(new PropertiesPropertySource("apis", properties));

        ApisProperties apisProperties;
        apisProperties = new ApisProperties();

        PropertiesConfigurationFactory configurationFactory;
        configurationFactory = new PropertiesConfigurationFactory<>(apisProperties);
        configurationFactory.setPropertySources(propertySources);
        configurationFactory.setTargetName("foo"); // it's the same prefix as the one defined in the @ConfigurationProperties

        configurationFactory.bindPropertiesToTarget();
        return apisProperties; // apiProperties are fed with the values defined in the application.yaml

    } catch (BindException e) {
        throw new IllegalArgumentException(e);

    }
}