In a spring boot project, how to load application.yaml into Java Properties

Question

If I have the following properties in application.yaml:

myPro:
   prop1: prop1value
   prop2: prop2value
....

Is there a way to load this into a Java Properties object?

Solution

By default, Spring already puts all those application properties in its environment which is a wrapper of Properties, for example:

@Autowired
private Environment environment;

public void stuff() {
    environment.getProperty("myPro.prop1");
    environment.getProperty("myPro.prop2");
}

---

However, if you just want to use the values, you can always use the @Value annotation, for example:

@Value("${myPro.prop1}")
private String prop1;
@Value("${myPro.prop2}")
private String prop2;

---

Lastly, if you really want a Properties object with just everything in myPro, you can create the following bean:

@ConfigurationProperties(prefix = "myPro")
@Bean
public Properties myProperties() {
    return new Properties();
}

Now you can autowire the properties and use them:

@Autowired
@Qualifier("myProperties")
private Properties myProperties;

public void stuff() {
    myProperties.getProperty("prop1");
    myProperties.getProperty("prop2");
}

In this case, you don't necessarily have to bind it to Properties, but you could use a custom POJO as well as long as it has a fieldname prop1 and another fieldname prop2.

These three options are also listed in the documentation:

Property values can be injected directly into your beans using the @Value annotation, accessed via Spring’s Environment abstraction or bound to structured objects via @ConfigurationProperties.