One more case of false-positive cycles detection [DATAMONGO-1652]

[spring-projects-issues]

Sergey Bykov opened DATAMONGO-1652 and commented

The cycles detector gives false warnings under some conditions. The issue occurs when there are multiple similar 'branches' in the tree of the included objects.

Example reproducing the issue

Full working example can be seen here: https://github.com/centibit/spring-data-mongodb-false-positive-cycle-detection

Main entity A includes two value objects B and C:

@Document(collection = "ROOT_ENTITY")
public class A {

    @Id
    public String id;

    /*
     * Workaround to fix the issue: just swap this.b and this.c here in this class :)
     */
    public B b;

    public C c;

}

Class B is not highly interesting, the only note is it must include some fields not of simple types, for example D (the contents of D doesn’t matter):

public class B {

    public D d;

}

Class C also includes B (it is crucial that B is included both in A and C):

public class C implements Serializable {

    public B b;

}

When the application with such a class structure boots, it gives a false warning: org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexResolver$CyclicPropertyReferenceException: Found cycle for field 'd' in type 'B' for path 'b' which was probably intended to fix such cases but still fails under some rare conditions.

Source of the problem

When MongoPersistentEntityIndexResolver searches for the cycles, it records the possible inclusion paths as a set of the strings, and then tries to match the current stringified path with the previously found paths. In this example ".b" is found to be a substring of "c.b", so it gives a false positive warning.

Note that C must include some non-simple fields (class D in the example), otherwise it would be outfiltered by the conditional logic in org.springframework.data.mapping.model.AbstractPersistentProperty.getTypeInformationIfEntityCandidate.

Quick workaround

Simply swap the lines public B b; and public C c; in the definition of the class A. In this case, traverse order changes, and the cycle detector will try to check whether "c.b" is a substring of ".b", which is not, and no warning will be issued :)

---

Affects: 1.10.1 (Ingalls SR1)

Reference URL: https://github.com/centibit/spring-data-mongodb-false-positive-cycle-detection

Issue Links:

• DATAMONGO-1782 CyclicPropertyReferenceException on index resolution
  ("is duplicated by")

[spring-projects-issues]

Mark Paluch commented

Will be fixed with DATAMONGO-1782