当 bean 构造函数使用参数时，Spring init 失败

Question

SpringBoot app fails while trying to initialize this class:

@Component
public class Weather {

private Map<Integer,Double> maxRainyDays;
private Map<Integer,  WeatherDays> totalDays;

public Weather(Map<Integer, WeatherDays> totalDays, Map<Integer,Double> maxRainyDays){

    this.setMaxRainyDays(maxRainyDays);
    this.setTotalDays(totalDays);

}

The error:

Parameter 0 of constructor in SolarSystem.Models.Weather required a bean of type 'SolarSystem.Utilities.WeatherDays' that could not be found.

The mentioned bean is already defined (in the same basepackage):

public enum WeatherDays {

RAINY,
MILD,
DRY,
MAX_RAIN}

Workaround:

When I changed to Weather() constructor I solved the issue.Of course I had to use setters to set the properties of the object.

But I need to understand the reasons why happened

Answer 1

Because the collections (Map here) you are injecting via constructor parameter aren't registered as Spring beans. This is why you would annotate class with @service , @repository , etc and have them autowired into other classes. To fix, you can set up a config class like such:

@Configuration
public class BeanConfig {

    @Bean
    public Map<Integer, WeatherDays> totalDays() {
        Map<Integer, WeatherDays> map = new HashMap<>();
        map.put(1, WeatherDays.DRY);
        return map;
    }

    @Bean
    public Map<Integer, Double> maxRainyDays() {
        Map<Integer, Double> map = new HashMap<>();
        map.put(1, 0.2);
        return map;
    }
}