Spring init failing when bean constructor using parameters

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

This class doesn't look like it should be a bean (service object); instead, it looks like it's a data object. — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Jan 10, 2019 at 0:28
Question, why do you consider to inject Weather as component? — Jonathan JOhx
– Jonathan JOhx, Commented Jan 10, 2019 at 2:54
@JonathanJohx because I'm autowiring into other Service in the package — moji
– moji, Commented Jan 10, 2019 at 2:59
Ok let me explain about it, first when you inject a Class in this context Weather as dependency then you need to pass an empty construct or a construct with parameters which they need to be injected as beans because when Spring scans all components, they should have an empty construct or parameters injected. Example public Weather (@Autowored Service service) {... } when a class is injected as component is more or less like a singleton class.. — Jonathan JOhx
– Jonathan JOhx, Commented Jan 10, 2019 at 3:11
Yes, you need it. For that you need to know if it's necessary creating a component called Weather or perhaps you need to create several instances from this Weather class. — Jonathan JOhx
– Jonathan JOhx, Commented Jan 10, 2019 at 3:36

夢のの夢 · Accepted Answer · 2019-01-10 00:48:28Z

2

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;
    }
}

answered Jan 10, 2019 at 0:48

夢のの夢

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2 Comments

moji Over a year ago

Good to know! So this is how you would normally inject POJOs or simple DTOs in your spring services? Thanks

夢のの夢 Over a year ago

Not quite, if you look at chrylis's comment. is your weather class meant to contain stateful data and instantiated many times? if so, it shouldn't be a bean and instead a service class (as a bean) should be used to set its state and create many Weather objects.

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