@Autowired in Spring custom converter

Question

I have custom converter:

  @Component
public class RoleConverter implements Converter<String, Role> {

    @Autowired private Roles roles;

    @Override
    public Role convert(String id) {
        return roles.findById(Long.parseLong(id));
    }
}

But @Autowired is setting null value. Causing Nullpointerexception.

This is Roles class:

@Repository
@Transactional
public class Roles extends Domain<Role>{

    public Roles() {
        super(Role.class);
    }

}

I'm using Java Configuration. Converter is registered:

@Configuration
@EnableWebMvc
//other annotations...
public class WebappConfig extends WebMvcConfigurerAdapter {
//....


    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addConverter(new RoleConverter());
        super.addFormatters(registry);
    }


/....

}

When I @Autowired Roles in controller its works.

Why @Autowired is setting null in Converter?

score 6 · Accepted Answer · edited Feb 04 '21 at 05:50

6

It is because here you are creating a new object of RoleConverter. Instead you should autowire the RoleConverter

Instead of

registry.addConverter(new RoleConverter());

Use

@Autowired
RoleConverter roleConverter;

@Override
public void addFormatters(FormatterRegistry registry)
{
    registry.addConverter(roleConverter);

}

edited Feb 04 '21 at 05:50

June7

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answered May 15 '13 at 04:04

Bhushan Bhangale

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Thanks! You are right. I didn't noticed that. Solved. – user1712326 May 15 '13 at 04:19
> Instead you should autowire the RoleConverter What exactly does this mean? – Avindra Goolcharan Apr 25 '20 at 00:18
life saver, thank you – Mohammad Yahia Feb 03 '21 at 18:52
Thanks. I was facing the same issue and it rectified with your solution. But can you please elaborate on your solution. Is it because spring's dependency injection will not work if parent classes are invoked using new keyword? – Ann Apr 05 '22 at 09:48

@Autowired in Spring custom converter

1 Answers1