I'm using Spring Boot 2.5.4 and am trying to initialize an immutable class from properties:
@Configuration
@ConfigurationProperties("test")
public class Config {
public final String foo;
@ConstructorBinding
public Config(String foo) {
this.foo = foo;
}
}
application.yml:
test:
foo: bar
Main class:
@SpringBootApplication
@ConfigurationPropertiesScan
public class Application implements CommandLineRunner {
@Autowired Config config;
public Application(Config config) {
this.config = config;
}
public static void main(String[] args) { SpringApplication.run(Application.class, args); }
@Override
public void run(String... args) {
System.out.println(config.foo);
}
}
I would expect this to start and print "bar". However, it fails to start with
Parameter 0 of constructor in Config required a bean of type 'java.lang.String' that could not be found.
When I remove the @ConstructorBinding
and add a setter and nullary constructor, it does work.
Add @ConstructorBinding
in class level. And remove @Configuration
annotation. Like this,
@ConstructorBinding
@ConfigurationProperties("test")
public class Config {
public final String foo;
public Config(String foo) {
this.foo = foo;
}
}