根据@qualifier名称生成spring bean

Question

Is it possible to create beans based on the value in Qualifier? I'm looking to be able to just mark Micrometer Counters/Gauges/etc... with a Qualifier containing the metric name.

@Autowired
@Qualifer("my.service.my.metric") Counter metric;

spring would give me:

metricRegister.counter("my.service.my.metric")

My google-fu is failing me and I don't see an obvious way of doing what I want.

edit more context: I'm just trying to get rid of the logic that happens in the constructor, and avoid Config boiler plate for each metric

Current Way:

@Service
class MyService {

  private Counter counter1;
  private Counter counter2;

  MyService(MeterRegistry registry) {
     this.counter1 = registry.counter("someMetric");
     this.counter2 = registry.counter("otherMetric");
  }
}

What I would like to work with a some sort of specialized beanFactory that sees the value/name in the Qualifier

@Service
class MyService {
  private Counter counter1;
  private Counter counter2;

  MyService(@Qualifer("someMetric") Counter counter1, @Qualifier("otherMetric") Counter counter2) {
    this.counter1 = counter1;
    this.counter2 = counter2;
  }
}

(I'll actually be using lombok for the constructer generation so I wouldn't even have a visible constructor)

Answer 1

You need to create your class with a qualifier name like: @Component("clsA") public class classA

and pass 'clsA' has a qualifier name

Answer 2

You need to giver your Bean/Component a name:

import org.springframework.stereotype.Component;

@Component("my.service.my.metric")
public class Counter {
    // Code
}

And after that you will be able to use:

@Autowired
@Qualifer("my.service.my.metric") 
Counter metric;

As mentioned in the Spring docs about the value that you are passing to the @Component

The value may indicate a suggestion for a logical component name, to be turned into a Spring bean in case of an autodetected component. @return the suggested component name, if any (or empty String otherwise)

Answer 3

I think what you need is a configuration class.

@Configuration
class MetricConfiguration {
    public static final String METRIC_1_NAME = "your.metric.name";
    public static final String METRIC_2_NAME = "your.other.metric.name";

    @Bean(METRIC_1_NAME)
    public Counter(MetricsRegistry registry) {
        return registry.counter(METRIC_1_NAME, counter);
    }

    @Bean(METRIC_2_NAME)
    public Counter(MetricsRegistry registry) {
        return registry.counter(METRIC_2_NAME, counter);
    }
}

Then you can inject them via

@Service
class YourService {
    @Autowired
    @Qualifier(MetricConfiguration.METRIC_1_NAME)
    Counter metric1Counter;
}

@Service
class YourOtherService {
    @Autowired
    @Qualifier(MetricConfiguration.METRIC_2_NAME)
    Counter metric2Counter;
}

Answer 4

Not exactly what you ask for, but I don't see how this is not equivalent.

Provide a factory bean

@Service public class CounterFactory {
    @Autowired private MeterRegistry registry;

    // cache already created counters; you could also use Spring's caching
    Map<String, Counter> createdCounters = new HashMap<>();

    public Counter createCounter(String metricName) {
        return createdCounters.computeIfAbsent(metricName, s -> registry.counter(s));
    }
}

Now you can NOT get Counter beans by using

@Service public class CounterClient {
    private static final String METRIC_NAME = "my_metric_name";
    @Autowired @Qualifier(METRIC_NAME)
    private Counter metric;

    public void triggerMetric() { metric.inc(); }
}

but like this which I think is just as good.

@Service public class CounterClient {
    private static final String METRIC_NAME = "my_metric_name";
    private Counter metric;

    CounterClient(CounterFactory factory) {
        metric = factory.createCounter(METRIC_NAME);
    }

    public void triggerMetric() { metric.inc(); }
}