Spring @Value("${}") often null

Question

I'm using Spring Boot application. In some @Component class @Value fields are loaded, instead on other classes they are always null.

Seems that @Value(s) are loaded after my @Bean/@Component are created.

I need to load some values from a properties file in my @Bean.

Have you some suggestion?

Are the "other classes" registered as spring beans? What is the difference between the ones that receive the values and the ones that don't? — Evgeni Dimitrov, Feb 20 '15 at 19:53

score 54 · Answer 1 · answered Feb 20 '15 at 20:17

54

The properties(and all of the bean dependencies) are injected after the bean is constructed(the execution of the constructor).

You can use constructor injection if you need them there.

@Component
public class SomeBean {
    private String prop;
    @Autowired
    public SomeBean(@Value("${some.prop}") String prop) {
        this.prop = prop;
        //use it here
    }
}

Another option is to move the constructor logic in method annotated with @PostConstruct it will be executed after the bean is created and all it's dependencies and property values are resolved.

answered Feb 20 '15 at 20:17

Evgeni Dimitrov

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And who will call this constructor? I'm trying but this 'custom' constructor is not called. – drenda Feb 20 '15 at 20:20
You probably also have the default and the custom constructor. Remove the one without parameters. – Evgeni Dimitrov Feb 20 '15 at 20:22
I can't because I've an exception removing default constructor: No default constructor found; nested exception is java.lang.NoSuchMethodException: it.modem.ModemManager.() – drenda Feb 20 '15 at 20:24
2

Then try with the @PostConstruct method – Evgeni Dimitrov Feb 20 '15 at 20:32
I yet done it. It works but I'm not in the constructor. So is not possibile have values inside the constructor? – drenda Feb 20 '15 at 20:33

score 1 · Answer 2 · answered Mar 18 '19 at 16:42

1

It can happen when you are resolving it into a static variable. I had observed this sometime back and resolved it just by removing static. As people always say, exercise caution while using static.

answered Mar 18 '19 at 16:42

mahesh chakravarthi

251
2
4

score 0 · Answer 3 · answered Feb 20 '15 at 19:24

0

Have you tried:

@Component
@PropertySource("file:/your/file/path")
public class MyBean {

  private @Value("${property}") String property;
  ...
}

answered Feb 20 '15 at 19:24

Efe Kahraman

1,438
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Using @PropertySource("classpath:application.properties") I've an Exception during startup: No qualifying bean of type [org.springframework.core.io.Resource] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@javax.inject.Inject()}. Thanks – drenda Feb 20 '15 at 19:49
Did you annotated the class with `@Component` ? – Efe Kahraman Feb 20 '15 at 20:28
Yes. @Evgeni has centered the problem. I can't user Value field inside the constructor as it is now. – drenda Feb 20 '15 at 20:30

score -2 · Answer 4 · answered Apr 11 '16 at 07:43

-2

Another possible reason is that the '@Value' lines are below the lines that need these properties/values.

I spent a lot of time debugging this problem, and found out that the order of lines matters!

answered Apr 11 '16 at 07:43

ghxin

1

Spring @Value("${}") often null

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