NPE with JsonBackReference when deserialized when using Lombok

Hello,

I’ve a problem while trying to upgrade from Jackson 2.6.x to Jackson 2.8.1. This upgrade is linked to a change of version of spring-boot.

While everything was working in 2.6.x, The deserialization is totally broken for me in 2.7 and 2.8.1. When I try to deserialized an entity having a @JsonBackReference annotation, I have a NullPointerException.

java.lang.NullPointerException
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.constructSettableProperty(BeanDeserializerFactory.java:733)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.addReferenceProperties(BeanDeserializerFactory.java:643)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.buildBeanDeserializer(BeanDeserializerFactory.java:230)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.createBeanDeserializer(BeanDeserializerFactory.java:141)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer2(DeserializerCache.java:406)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:352)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:264)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
    at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:142)
    at com.fasterxml.jackson.databind.DeserializationContext.findContextualValueDeserializer(DeserializationContext.java:442)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.createContextual(CollectionDeserializer.java:196)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.createContextual(CollectionDeserializer.java:26)
    at com.fasterxml.jackson.databind.DeserializationContext.handleSecondaryContextualization(DeserializationContext.java:680)
    at com.fasterxml.jackson.databind.DeserializationContext.findContextualValueDeserializer(DeserializationContext.java:444)
    at com.fasterxml.jackson.databind.deser.impl.PropertyBasedCreator.construct(PropertyBasedCreator.java:79)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.resolve(BeanDeserializerBase.java:606)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:296)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
    at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:142)
    at com.fasterxml.jackson.databind.DeserializationContext.findRootValueDeserializer(DeserializationContext.java:475)
    at com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:3890)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3785)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2833)
    at com.github.davinkevin.issueJackson.entity.PodcastTest.should_serialized(PodcastTest.java:24)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

I’ve extract the entity in a separate project to verify if the spring environment was a source of the problem, but this NPE also appear in a simple project.

You can find the sample project here : https://github.com/davinkevin/issue-jackson-deserialize-2.7

The test which causes this problem is :

    @Test
    public void should_serialized() throws IOException {
        /* Given */
        String podcastAsText = "{\"hasToBeDeleted\":true,\"cover\":{\"id\":null,\"url\":\"https://yt3.ggpht.com/-2eu-eG4PLa8/AAAAAAAAAAI/AAAAAAAAAAA/FZUzswUhAmI/s100-c-k-no-rj-c0xffffff/photo.jpg\",\"width\":200,\"height\":200},\"url\":\"https://www.youtube.com/channel/UC_yP2DpIgs5Y1uWC0T03Chw\",\"type\":\"Youtube\",\"title\":\"Joueur Du Grenier\",\"description\":\"Test de jeux à la con !\"}";

        /* When */
        Podcast podcast1 = objectMapper.readValue(podcastAsText, Podcast.class);

        /* Then */
        assertThat(podcast1).isNotNull();
    }

and you can find here the entity Podcast and Item.

I’ve searched for an issue linked to that, without success in StackOverflow and in the issue tracker.

Thanks for your help

[Serializator]

@cowtowncoder Is there any chance that you might know a reason why a field annotated with @JsonManagedReference doesn’t get deserialized and stays null and when @JsonManagedReference isn’t used it does actually get properly deserialized?

Sorry for not providing any information on how I use it, I’m currently not on my PC.

[acaliaro]

I have had the same problem.

My solution is:

remove

@AllArgsConstructor @NoArgsConstructor

and create them in code