Can we use @Autowired annotation as a constructor argument?

Question

In my case I am trying to use Environment class to read properties. I tried two options.

Option 1 - I tried to use @Autowired the Enviornment class as shown in the following example.

@Service("idmHelper")
public class IdmHelper {

    @Autowired
    Environment env;

    public IdmHelper() {
       env.getProperty('property-name')
       ...
   }
}

Here it gives a NullPointerException. Becuase env is null.

Option 2 - I tried to use @Autowired inside the constructor as an argument, as shown in the following example.

@Service("idmHelper")
public class IdmHelper {

    public IdmHelper(@Autowired Environment env) {
       env.getProperty('property-name')
       ...
   }
}

Here the env will get an object and I can access the properties. But I am getting the following error;

enter image description here

I am new to spring-boot, can someone explain why I am getting this error. I doubt that it is something to do with initiating the constructor. Please correct me If I am wrong.

This is my full code; Full-code-of-idm-helper-class

You don't even need the `@Autowired` annotation on the parameter of the constructor (unless you're using an old version of Spring). But you do need to have `Environment` configured as a Spring bean. — Jesper, Jul 05 '22 at 08:12
@dunni The line is - `public IdmHelper(@Autowired Environment env) {` — Hashan Maduwantha, Jul 05 '22 at 08:19
Doubtful that this line causes a NPE. Can you show your real code? — dunni, Jul 05 '22 at 08:22
@HashanMaduwantha i doubt that. The line that throws the NPE is `env.getProperty`. — f1sh, Jul 05 '22 at 08:23
@dunni I have added the full code with a debug poing at the end please have a look. — Hashan Maduwantha, Jul 05 '22 at 08:38
@f1sh I have added a debug point, you can see env.getproperty works fine. — Hashan Maduwantha, Jul 05 '22 at 08:39
And which line now causes the exception? Your code doesn't fit to the exception that you posted. — dunni, Jul 05 '22 at 08:40
@dunni yeah I did some changes and That's why it is changed. I ll run again and let you know the exact line. — Hashan Maduwantha, Jul 05 '22 at 08:42
Your screenshot shows there's wayyy much more going on than what you posted. The autowiring works. You just have a regular NullPointerException somewhere. Why didn't you include your code from the start? You have people guessing for 45 minutes here. — f1sh, Jul 05 '22 at 08:51
@f1sh I was trying to be more specific because of you peoples' ease, also the code is very large, that is why i pointed out the location where error occurs. let me reformat the issue. — Hashan Maduwantha, Jul 05 '22 at 09:00

Zorglube · Accepted Answer · 2022-07-05T11:21:18.957

0

Try:

@Service("idmHelper")
public class IdmHelper {

    @Autowired
    Environment env;
    private var prop = null ; 

    @PostConstruct
    public init() {
       prop = env.getProperty('property-name');
   }
}

Can we use @Autowired annotation as a constructor argument?

1 Answers1