Flaky behavior of Jackson Deserialization: "No _valueDeserializer assigned"

Question

I have a problem with Jackson's deserialization mechanism in Spring Boot. My domain classes look like this:

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class Post {
    // ...

    @ManyToOne
    @JsonIncludeProperties({ "id", "course" })
    private Lecture lecture;

    @ManyToOne
    @JsonIncludeProperties({ "id" })
    private Course course;
}

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class Lecture {
    // ...
    
    @JsonIgnoreProperties(value = { "lectures", "posts" }, allowSetters = true)
    private Course course;
}

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class Course {
    // ...

    @JsonIgnoreProperties(value = "course", allowSetters = true)
    private Set lectures = new HashSet<>();

    @JsonIgnoreProperties("course")
    private Set posts = new HashSet<>();
}

Now to test the creation of Posts which have a Lecture set, I'm trying to test them by using the MockMvc bean. Therefore, I'm doing the following:

creating an object of type Post,
sending it via an HTTP POST to my RestController, and
deserializing the JSON response back to Post.class.

Everything works fine, but step (3) works only approx. 9/10 times (it never fails on my local setup, but only in the CI pipeline, which makes it a very hard to debug flaky test).

Post postToSave = generatePost();
postToSave.setLecture(generateLecture());
Post createdPost = request.postWithResponseBody("/api/post", postToSave, Post.class);

The error log looks like this:

com.fasterxml.jackson.databind.exc.MismatchedInputException: No _valueDeserializer assigned ... (through reference chain: a.b.c.Post["lecture"]->a.b.c.Lecture["course"])
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1575)
at com.fasterxml.jackson.databind.deser.impl.FailingDeserializer.deserialize(FailingDeserializer.java:33)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:402)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:195)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:402)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:195)
at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3548)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3516)

I would appreciate any help on this issue.

Flaky behavior of Jackson Deserialization: "No _valueDeserializer assigned"

0 Answers