@ConditionalOnProperty for multi-valued properies

问题

Is there any way to use @ConditionalOnProperty annotation based on multi-valued property?

Spring configuration:

@Bean
@ConditionalOnProperty(name = "prop", havingValue = "a")
public SomeBean bean1() {
    return new SomeBean1();
}

@Bean
@ConditionalOnProperty(name = "prop", havingValue = "b")
public SomeBean bean2() {
    return new SomeBean2();
}

and application.yaml

prop: 
 - a
 - b

I expect that both beans: bean1 and bean2 will be registered in the spring context, but no one from them isn't registered. Is there any way to do it?

回答1:

You can use Spring Boot @ConditionalOnExpression annotation, not just in the @bean-annotated methods, but directly on classes as well:

@ConditionalOnExpression("${my.prop}")
@Component
class SomeBean1 implements SomeBean {}

@ConditionalOnExpression("!${my.prop}")
@Component
class SomeBean2 implements SomeBean {}

Having said this I personally prefer using pure Java:

@Value("${my.prop}") String myProp;
...
@Bean SomeBean someBean() {
    if ("abc".equals(myProp)) {return new SomeBean1();} else {return new SomeBean2();}
}

回答2:

It looks like @ConditionalOnProperty haven't multivalued properies. In spring environment they are presented as

prop[0]=a
prop[1]=b

My solution is to make my own @Conditional extension, that is able to work with multivalued properies. Here is the example.

Annotation:

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD })
@Documented
@Conditional(OnPropertyCondition.class)
public @interface ConditionalOnProperty2 {
    String name();
    String value();
}

Condition:

class OnPropertyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        String name = attribute(metadata, "name");
        String value = attribute(metadata, "value");

        String searchName = name;
        String property = property(context, searchName);
        int i = 0;
        do {
            if (value.equals(property)) return true;
            searchName = name + '[' + i++ + ']';
        } while ((property = property(context, searchName)) != null);
        return false;
    }

    private String attribute(AnnotatedTypeMetadata metadata, String name) {
        return (String) metadata.getAnnotationAttributes(ConditionalOnProperty2.class.getName()).get(name);
    }

    private String property(ConditionContext context, String name) {
        return context.getEnvironment().getProperty(name);
    }
}

Usage:

 @Bean
 @ConditionalOnProperty2(name = "prop", havingValue = "a")
 public SomeBean bean1() {
     return new SomeBean1();
 }

 @Bean
 @ConditionalOnProperty2(name = "prop", havingValue = "b")
 public SomeBean bean2() {
     return new SomeBean2();
 }

来源：https://stackoverflow.com/questions/37969140/conditionalonproperty-for-multi-valued-properies

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java

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spring-boot

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