Error when the member of Entity class used in SpringWebFlux is final

This is a completely personal memo. It's a good level on Twitter, but here to leave it.

When I somehow created the Entity class used in Spring Data MongoDB, I got an error. I get an error saying "Setter". If you try it with a Setter, it will certainly work. But why did you just find One and return it? ?? ??

error

This application has no configured error view, so you are seeing this as a fallback.

Mon Feb 18 06:27:46 JST 2019
There was an unexpected error (type=Internal Server Error, status=500).
No accessor to set property @org.springframework.data.annotation.Id()private final java.lang.Integer com.example.demo.Flower.id!
java.lang.UnsupportedOperationException: No accessor to set property @org.springframework.data.annotation.Id()private final java.lang.Integer com.example.demo.Flower.id!
	at com.example.demo.Flower_Accessor_jjo0e1.setProperty(Unknown Source)
	at org.springframework.data.mapping.model.ConvertingPropertyAccessor.setProperty(ConvertingPropertyAccessor.java:61)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readAndPopulateIdentifier(MappingMongoConverter.java:326)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.populateProperties(MappingMongoConverter.java:289)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:275)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:245)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:194)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:190)
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:78)
	at org.springframework.data.mongodb.core.ReactiveMongoTemplate$ReadDocumentCallback.doWith(ReactiveMongoTemplate.java:2910)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:107)
	at reactor.core.publisher.FluxOnAssembly$OnAssemblySubscriber.onNext(FluxOnAssembly.java:353)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:76)
	at com.mongodb.reactivestreams.client.internal.ObservableToPublisher$1.onNext(ObservableToPublisher.java:68)
...

If you try changing the code a little or read the big error carefully ... Ah, if you make it final, it won't work at Convert. Understood by the atmosphere.

Even without the setter, it worked when I removed only the final. There are various things behind the scenes.

@Document
public class Flower {
	@Id
	private Integer id;
	private String name;
	private String color;
	
	Flower(){
		id = null;
		name = "";
		color = "";
	}
	Flower(int id, String name, String color){
		this.id = id;
		this.name = name;
		this.color = color;
	}
	
	public Integer getId() {
		return this.id;
	}
	public String getName() {
		return this.name;
	}
	public String getColor() {
		return this.color;
	}
}