Inject Properties From YAML in Spring

In Spring, we can easily define configuration value in a YAML file, and inject those configuration into a Java class.

Take the following the YAML configuration file as an example.

YAML

server: localhost

# by default, spring split the string with comma
listValues: a,b,c,d
# if we want to split the string with customize character, we can use Spring EL
listValuesWithSpEL: a,b;c,d;e,f

# we can inject the whole complexObject into another class, with annotation ConfigurationProperties
complexObject:
    port: 90
    ssl: false
    listValues: a,b,c,d
    listValuesWithSpEL: a,b;c,d;e,f

We can create a Java bean class to inject those configurations.

Java

@Configuration
public class PropertyConfig {
    @Value("${server}")
    private String server;

    @Value("${listValues}")
    private String[] listValues;

    @Value("#{'${listValuesWithSpEL}'.split(';')}")
    private String[] listValuesWithSpEL;

    // if it not set, it will use default value 'false'
    @Value("${enabled:false}")
    private boolean enabled;
}

@Configuration
@ConfigurationProperties(prefix = "complexObject") 
public class ComplexObject {
    @Value("${port}")
    private int port;

    @Value("${ssl}")
    private boolean ssl;

    @Value("#{'${listValuesWithSpEL}'.split(';')}")
    private String[] listValuesWithSpEL;

    @Value("${complexObject}")
    private ComplexObject complexObject;
}