I am working on a Spring Boot application using Neo4j as the database. I have a UserEntity class that has a relationship with UserContactEntity. However, when I run a query to fetch UserEntity along with its contacts, the contacts field is always null.

Here are the relevant parts of my code:

UserEntity.kt:

@NodeEntity("User")
class UserEntity : PermissionableEntity, Serializable {
    @Id
    @Property("userId")
    var userId: StringID? = null

    @Relationship("PERSON_HAS_CONTACT")
    var contacts: MutableSet<UserContactEntity> = mutableSetOf()

    // Other fields and methods...
}

UserContactEntity.kt:

@NodeEntity("UserContact")
class UserContactEntity : Serializable {
    // Fields and methods...
}

UserRepository.kt:

interface UserRepository : Neo4jRepository<UserEntity, StringID> {

    fun findByUserIdIn(userIds: Collection<StringID>, @Depth depth: Int = 2): Iterable<UserEntity>
    
    @Query("MATCH (u:User)-[:PERSON_HAS_CONTACT]->(c:UserContact) WHERE u.userId IN $userIds RETURN u, collect(c)")
    fun findByUserIdInWithContacts(@Param("userIds") userIds: Collection<StringID>): Iterable<UserEntity>
}

If I run this query in the database using the Neo4J browser, I can see that contacts are associated correctly with the users.

MATCH (u:User)-[r:PERSON_HAS_CONTACT]->(c:UserContact)
RETURN u.userId AS userId, c.id AS contactId, c.type AS contactType, c.detail AS contactDetail, c.verified AS contactVerified

I have tried both of the following methods to solve the problem:

1. Using the findByUserIdIn method, which takes a collection of StringID and an optional depth parameter to retrieve UserEntity objects.
2. Using the findByUserIdInWithContacts method, which is a custom query that matches User nodes with UserContact nodes and returns the user along with their contacts.

Despite the query and the relationship definition, the contacts field in UserEntity is always null. What could be causing this issue, and how can I ensure that the contacts field is correctly populated?

Are there any known issues with Spring Data Neo4j or Neo4j, or could a bug somewhere else in my application be causing this issue?

Versions:

• Neo4j 4.1.1 enterprise
• Spring Boot 2.3.8.RELEASE
• Java 11