Spring Framework needs @Nonbinding like support

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This example shows why we could use @Nonbinding like support in Qualifier annotations (as known from CDI)

Annotation :: Lowercase.java

package com.moelholm;

import org.springframework.beans.factory.annotation.Qualifier;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
public @interface Lowercase {
  String value() default "";
}

Annotation :: Uppercase.java

package com.moelholm;

import org.springframework.beans.factory.annotation.Qualifier;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
public @interface Uppercase {
  String value() default "";
}

GreeterService.java

package com.moelholm;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class GreeterService {

  @Autowired
  @Uppercase("hElLo WoRlD")
  private String upper;

  @Autowired
  @Lowercase("hElLo WoRlD")
  private String lower;

  public String sayHello(String caller) {
    return String.format("%s (%s), %s", upper, lower, caller);
  }

}

MyBeanConfig.java

package com.moelholm;

import static org.springframework.core.annotation.AnnotationUtils.findAnnotation;

import org.springframework.beans.factory.InjectionPoint;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;

@Configuration
public class MyBeanConfig {

  @Bean
  @Uppercase("hElLo WoRlD")// Spring needs @Nonbinding so that we can remove this 'value'
  @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
  public String uppercase(InjectionPoint ip) {
    Uppercase annotation = findAnnotation(ip.getAnnotatedElement(), Uppercase.class);
    return annotation.value().toUpperCase();
  }

  @Bean
  @Lowercase("hElLo WoRlD")// Spring needs @Nonbinding so that we can remove this 'value'
  @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
  public String lowercase(InjectionPoint ip) {
    Lowercase annotation = findAnnotation(ip.getAnnotatedElement(), Lowercase.class);
    return annotation.value().toLowerCase();
  }

}

Point taken, this looks like a worthwhile scenario, even I haven't encountered this in practice yet. I wouldn't bake the non-binding part into the annotation type though; I'd intuitively rather specify something like @Uppercase("*") to express such a flexible match on the @Bean method. Along such lines, a specified value wouldn't get silently ignored, making the bean declaration's intention more obvious.

In any case, if you'd like to see a first-class way of modelling such a scenario in Spring, please raise it on our JIRA.

- import org.springframework.beans.factory.annotation.Qualifier;
+ import javax.inject.Qualifier;

Hi Juergen,

Thank you for taking a look at this.

To be honest I think the "need" is new - comes with the InjectionPoint introduction. That is also why I think it hasn't been raised before.

I do still think that non binding support makes sense for non string attribute values as well. Although probably not as useful for practical purposes.

Just my two cents :)