Cannot resolve targetEntity in EntityFromDtoInstantiatingConverter.

[meistermeier]

This issue still occurs in 6.2.2. The NPE is now on line 77:

PreferredConstructor> constructor = targetEntity
.getPersistenceConstructor();

Originally posted by @seabamirum in #2395 (comment)

[meistermeier]

This might be something different. But I wonder how the targetEntity should become null if you are requesting a known type. Can you provide a reproducer?

[seabamirum]

Hello! My class extends org.springframework.security.core.userdetails.User, but the error occurs even with this simple User class below, with a single Boolean (error occurs with either primitive or wrapper type) constructor argument. I stepped it pretty deep into the debugger and found that AbstractMappingContext getPersistentEntity(TypeInformation<?> type) was returning NULL for boolean types.

User u = new User(true);
reactiveNeo4jTemplate.save(User.class).one(u);

encounters the following NPE:

java.lang.NullPointerException: null
	at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.convert(EntityFromDtoInstantiatingConverter.java:78) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
...
Original Stack Trace:
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.convert(EntityFromDtoInstantiatingConverter.java:78) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.getPropertyValueFor(EntityFromDtoInstantiatingConverter.java:136) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter$1.getParameterValue(EntityFromDtoInstantiatingConverter.java:90) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.extractInvocationArguments(ClassGeneratingEntityInstantiator.java:276) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator$EntityInstantiatorAdapter.createInstance(ClassGeneratingEntityInstantiator.java:248) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:89) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.convert(EntityFromDtoInstantiatingConverter.java:82) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195) ~[na:na]
		at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655) ~[na:na]
		at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[na:na]
		at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[na:na]
		at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) ~[na:na]
		at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) ~[na:na]
		at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
		at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497) ~[na:na]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.getPropertyValueFor(EntityFromDtoInstantiatingConverter.java:129) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.lambda$convert$0(EntityFromDtoInstantiatingConverter.java:100) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.mapping.PersistentEntity.lambda$doWithAll$0(PersistentEntity.java:257) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.mapping.model.BasicPersistentEntity.doWithAssociations(BasicPersistentEntity.java:387) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.mapping.PersistentEntity.doWithAll(PersistentEntity.java:256) ~[spring-data-commons-2.6.2.jar:2.6.2]
		at org.springframework.data.neo4j.core.mapping.EntityFromDtoInstantiatingConverter.convert(EntityFromDtoInstantiatingConverter.java:95) ~[spring-data-neo4j-6.2.2.jar:6.2.2]
		at org.springframework.data.neo4j.core.ReactiveNeo4jTemplate.lambda$doSave$6(ReactiveNeo4jTemplate.java:377) ~[spring-data-neo4j-6.2.2.jar:6.2.2]

My simple User class is below

import org.springframework.data.neo4j.core.schema.GeneratedValue;
import org.springframework.data.neo4j.core.schema.Id;
import org.springframework.data.neo4j.core.schema.Node;

@Node
public class User 
{
	@Id @GeneratedValue private Long userId;
	
	private final Boolean enabled;

	public User(Boolean enabled) 
	{
		super();
		this.enabled = enabled;
	}

	public Boolean getEnabled() {
		return enabled;
	}

	public Long getUserId() {
		return userId;
	}
}```

[meistermeier]

I created an example based on your given explanation about the problem (https://github.com/meistermeier/neo4j-issues-examples/tree/master/gh-2505).
This works out of the box with SDN 6.2.2. I even tried various mutations but could not get the exception.
Also I think that requesting getPersistenceEntity(Boolean.class) would already be the problem because this should only happen for real entities not primitives or their box types.
Could you compare where the differences are?

[seabamirum]

I think you're right that the problem is the call itself. My property value is a wrapped Boolean (false) but the target property type is a primitive Class (boolean), so it is entering this code block on line 133 when it shouldn't be.

if (propertyValue != null && !targetPropertyType.isInstance(propertyValue)) {

isInstance() always returns false for primitive type Class objects. Unfortunately I can't reproduce this anymore with my simple User example :( will keep trying.

[seabamirum]

Ah, I don't encounter the error unless I actually return the Mono in the repo method

@Override
	public Mono<User> testUserSave() 
	{
		User u = new User(true);
		return reactiveNeo4jTemplate.save(User.class).one(u);
	}

[seabamirum]

I also see these warnings in the logs

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.springframework.util.ReflectionUtils (file:/home/seab/.m2/repository/org/springframework/spring-core/5.3.16/spring-core-5.3.16.jar) to field java.lang.Boolean.value
WARNING: Please consider reporting this to the maintainers of org.springframework.util.ReflectionUtils
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

[seabamirum]

Okay, I'm running the same test now that you created in https://github.com/meistermeier/neo4j-issues-examples and it fails :(

[seabamirum]

if I change the enabled field and constructor argument from boolean to Boolean then the test passes.

[seabamirum]

In your User class (and also the original one I provided, oops) the type is Boolean, so that is why the test passed in that case. I think this should be enough now to track down the issue.

https://github.com/meistermeier/neo4j-issues-examples/blob/88629c9660009073a2d937d162a5639533d10307/gh-2505/src/main/java/com/example/gh2505/User.java#L8

[meistermeier]

Thanks for the investigation. And you are 100% right. The EntityFromDtoInstantiatingConverter assumes every property type to be an entity. Which does not make any real problems if a matching constructor exists. When it come to primitive types this gets problematic ;)

[meistermeier]

You could check out the 6.2.4-GH-2505-SNAPSHOT (available in ~30 minutes)
Side note: Using the fluent API is meant for projections, we do not mention this explicitly enough in the API and I will add this as part of this bug fix. If you just want to store a domain object, you should use template.save(object) and not template.save(Object's class).one(object).