How to autowire properties bean from Condition

Question

Does have anyone way to autowire bean in Condition?

There is an next example. We have 2 implementation of FileManager. One of implementation should be initialize in depends on property 'platform'. Properties handles via Archaius.

@Component
public class AwsPlatformCondition implements Condition {

    @Autowired
    private ArchaiusProperties archaiusProperties;

    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        return "aws".equalsIgnoreCase(archaiusProperties.getStringProperty(PropertiesMapper.PLATFORM));
    }
}

.

@Component
public class StandardPlatformCondition implements Condition {

    @Autowired
    private ArchaiusProperties archaiusProperties;

    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        return "standard".equalsIgnoreCase(archaiusProperties.getStringProperty(PropertiesMapper.PLATFORM));
    }
}

.

@Component
@Conditional(AwsPlatformCondition.class)
public class AS3FileManager implements FileManager {
...
}

.

@Component
@Conditional(StandardPlatformCondition.class)
public class NativeFileManager implements FileManager {
...
}

This code doesn't work. Main reason is because ArchaiusProperties bean doesn't initialized when condition matches. Does have anyone way to initialize ArchaiusProperties bean before using it in condition?

Stately

Answer 1

If we have a look at java docs for Condition interface -

Conditions must follow the same restrictions as BeanFactoryPostProcessor and take care to never interact with bean instances.

The restrictions are (from java docs of BeanFactoryPostProcessor)

A BeanFactoryPostProcessor may interact with and modify bean definitions, but never bean instances. Doing so may cause premature bean instantiation, violating the container and causing unintended side-effects.

So what you are trying to achieve is something not recommended; side effects of which already encountered.

However if we dig further in docs for Condition we get

For more fine-grained control of conditions that interact with @Configuration beans consider the ConfigurationCondition interface.

Here as well the restrictions are in violation. Thus all in all using Condition in this scenario is not a good idea.

So IMO the best bet for you is to go with @Profile where you can activate the desired profile at a time and use the respective bean; without considering the frills attached.

Madonia

Thanks! Now I actually think that @Conditional is not a best way for me. – Stately

Setting the profile would depend on the result returned from method in ArchaiusProperties bean. How is it possible? Also, doesn't the cited Javadoc say that you actually can refer to beans inside the ConfigurationCondition? – Masuria

Answer 2

To get system properties in Condition, I use conditionContext.getEnvironment().getProperty("app.x.y.z", String.class);

Daliadalila