@Value("${model.version:2}") is not taking up the default value = 2

I have a spring application in which I have put the code as below and I'm passing mvn parameter to update the value. The problem is every time I pass the value, regardless of the value it takes 0 by default. Can you please help me solve the issue.

Here is my little code snippet

@Value("${model.version:2}")
private int model;

public test class(){
    if(model == 2){
        <some logic>
    }
}

using mvn parameter as -Dmodel.version=2

In short: You are not using a spring managed context.

Let's walk through this together.

Assuming a class MyCoolClass like:

@Component
public class MyCoolClass {
    @Value("${some.value:3}")
    private int a;

    public void show() {
        log.info("a is " + a);
    }
}

If you autowire it and call show() it logs

> a is 3

Now let's create a test to verify it really works:

@SpringBootTest
public class MyTest {

    @Autowired
    private MyCoolClass myCoolClass;

    @Test
    public void lookAtMe() {
        myCoolClass.show();
    }
}

This initially throws a NPE, because this.myCoolClass is null; a first hint on something not working properly. Let's just overcome this and instanciate myCoolClass on ourselves:

this.myCoolClass = new MyCoolClass();
this.myCoolClass.show()

> a is 0

The clue here is, if you create a MyCoolClass instance on your own, there's nobody who parses the @Value annotation and processes the expressions for you. It's just an ordinary POJO.

To fix that, one adds @RunWith(SpringJUnit4ClassRunner.class) to the class and et viola, the log runs a whole Spring Application startup and logs a is 3! (of course without the user-created constructor-call):

@SpringBootTest
@Slf4j
@RunWith(SpringJUnit4ClassRunner.class)
public class mytest {
    @Autowired
    private MyCoolClass myCoolClass;

    @Test
    public void lookAtMe() {
        myCoolClass.show();
    }
}

And that's how the log looks:

 .   ____          _            __ _ _
/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/  ___)| |_)| | | | | || (_| |  ) ) ) )
'  |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot ::       (v2.1.13.RELEASE)

12:41:59  INFO 912 --- [      main] com.example.demo.MyTest                 : Starting MyTest on clijsters-computer with PID 912 (started by dclijsters in C:\demo)
12:41:59  INFO 912 --- [      main] com.example.demo.MyTest                 : No active profile set, falling back to default profiles: default
12:42:01  INFO 912 --- [      main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
12:42:02  INFO 912 --- [      main] o.s.s.c.ThreadPoolTaskScheduler         : Initializing ExecutorService 'taskScheduler'
12:42:02  INFO 912 --- [      main] com.example.demo.MyTest                 : Started MyTest in 2.513 seconds (JVM running for 3.376)
12:42:02  INFO 912 --- [      main] com.example.demo.MyTest                 : a is 3
12:42:02  INFO 912 --- [  Thread-3] o.s.s.c.ThreadPoolTaskScheduler         : Shutting down ExecutorService 'taskScheduler'
12:42:02  INFO 912 --- [  Thread-3] o.s.s.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'applicationTaskExecutor'