Spring @CondiitonalOnProperty, how to match only if missing

Question

I have two factory methods:

@Bean
@ConditionalOnProperty("some.property.text")
public Apple createAppleX() {}

and

@Bean
@ConditionalOnProperty("some.property.text", matchIfMissing=true)
public Apple createAppleY() {}

In case of not having "some.property.text" property at all - second method works fine and first one is ignored, which is desired behavior.

In case we have some string set to "some.property.text" - both methods are considered valid for producing Apple objects, which leads the application to fail with error "No qualifying bean of type".

Is it possible to avoid second method to be considered as factory method in case we have some value for the property? Especially, is it possible via annotations only?

Answer 1

I was facing same problem and here is my solution:

@Bean
@ConditionalOnProperty("some.property.text")
public Apple createAppleX() {}

@Bean
@ConditionalOnProperty("some.property.text", matchIfMissing=true, havingValue="value_that_never_appears")
public Apple createAppleY() {}

Answer 2

You can use NoneNestedConditions to negate one or more nested conditions. Something like this:

class NoSomePropertyCondition extends NoneNestedConditions {

    NoSomePropertyCondition() {
        super(ConfigurationPhase.PARSE_CONFIGURATION);
    }

    @ConditionalOnProperty("some.property.text")
    static class SomePropertyCondition {

    }

}

You can then use this custom condition on one of your bean methods:

@Bean
@ConditionalOnProperty("some.property.text")
public Apple createAppleX() {}

@Bean
@Conditional(NoSomePropertyCondition.class)
public Apple createAppleY() {}

Answer 3

In the spirit of one-upmanship, Here is a more reusable annotation:

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD })
@Conditional(ConditionalOnMissingProperty.MissingPropertyCondition.class)
public @interface ConditionalOnMissingProperty {

    String PROPERTY_KEYS = "propertyKeys";

    @AliasFor(PROPERTY_KEYS)
    String[] value() default {};

    @AliasFor("value")
    String[] propertyKeys() default {};

    class MissingPropertyCondition extends SpringBootCondition {
        @Override
        public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
            String[] keys = (String[]) metadata.getAnnotationAttributes(ConditionalOnMissingProperty.class.getName()).get(PROPERTY_KEYS);
            if (keys.length > 0) {
                boolean allMissing = true;
                for (String key : keys) {
                    String propertyValue = context.getEnvironment().getProperty(key);
                    String propertyValueList = context.getEnvironment().getProperty(key + "[0]"); //in case of list
                    allMissing &= (StringUtils.isEmpty(propertyValue) && StringUtils.isEmpty(propertyValueList));
                }
                if (allMissing) {
                    return new ConditionOutcome(true, "The following properties were all null or empty in the environment: " + Arrays.toString(keys));
                }
                return new ConditionOutcome(false, "one or more properties were found.");
            } else {
                throw new RuntimeException("expected method annotated with " + ConditionalOnMissingProperty.class.getName() + " to include a non-empty " + PROPERTY_KEYS + " attribute");
            }
        }
    }
}

Annotated beans or configuration are activated when one or more mentioned properties all do not exist:

@ConditionalOnMissingProperty({"app.foo.bar"})
@Configuration
public class SomeConfiguration {
  //... won't run if there is an app.foo.bar property with non-empty contents.
}

Later if I add more comprehensive reporting to the false outcome, I'll add it here.