Polymorphism doesn't work when Spring Boot Dev Tools are loaded

[Guerric-P]

I recently encountered a problem while developing locally with Spring Boot Dev Tools enabled (reproduced from 2.6.4 to 2.7.1).

I'm not sure if you want to fix this, I'm not even sure if it's a Spring Data related issue or not.

Given this code:

@Getter
@Setter
@RedisHash
class Root {
    private Base base;
}
    
public interface Base {

}
    
@Getter
@Setter
public class Implementor implements Base {
    // ...
}

public class CustomKeyspaceConfiguration extends KeyspaceConfiguration {
	private final String prefix;
	
	public CustomKeyspaceConfiguration(String prefix) {
		super();
		
		this.prefix = prefix;
	}
	
	@Override
	public boolean hasSettingsFor(Class<?> type) {
		if (super.hasSettingsFor(type) == false) {
			KeyspaceSettings settings = new KeyspaceSettings(type, prefix + ClassUtils.getUserClass(type).getName());
			addKeyspaceSettings(settings);
		}
		
		return true;
	}
}

I have a CrudRepository for the Root class which allows me to successfully store objects of that type in Redis.

But when I retrieve an object with a simple findById, I get this error:

Failed to instantiate some.package.name.Base using constructor NO_CONSTRUCTOR with arguments

However, the _class attribute is correctly set in Redis for that property:

base._class: some.package.name.Implementor

Explanation:

Spring Data has this piece of code:

Class<?> documentsTargetType = getDefaultedTypeToBeUsed(source);
    
if (documentsTargetType == null) {
    return basicType;
}

Class<T> rawType = basicType.getType();
    
boolean isMoreConcreteCustomType = (rawType == null)
    || (rawType.isAssignableFrom(documentsTargetType) && !rawType.equals(documentsTargetType));
    
if (!isMoreConcreteCustomType) {
    return basicType;
}

In my example, documentsTargetType contains Implementor and basicType contains Base. The rawType.isAssignableFrom(documentsTargetType) condition is supposed to return true, but it actually returns false, because Base and Implementor are loaded by different classloaders.

This results in an attempt to call the constructor of an interface which makes the deserialization of the entity fail.

[mp911de]

I have difficulties reproducing the issue. Can you please provide a reproducer, ideally through a GitHub repository?

[Guerric-P]

I was pretty sure that the specificity causing this bug in my project was the CustomKeyspaceConfiguration but indeed that minimal setup does not generate the bug.

I'll let you know if I find an actual minimal reproducible example. If you have any feeling about the possible cause, please let me know.

[spring-projects-issues]

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[spring-projects-issues]

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