Problem with multi-argument Creator with `@JsonBackReference` property

[sarahlikesglitter]

For the error, please refer to this github example for a consistent repro: https://github.com/atribe/ReproducingBug

The short summary of the issue is that Jackson 2.7.+ - 2.8.6 is not correctly setting up the setter methods for properties defined in my class that I want to deserialize when those classes have managed/back references. Also, another issue is that @JsonProperty and @JsonSetter annotation is ignored, so there isn't a way to explicitly provide your own setter methods for the properties.

Below is the trace of debugging I have done on this issue.

I have a simple JSON file that shows a ParentObject and a ChildObject. The ParentObject has a managed reference that is a list of its children. The ChildObject has a back reference to its parent object.

In Jackson 2.6.7, when I run the deserializer for these objects, it will properly handle the references and generating mutators for those properties that have dependencies.

In Jackson 2.7.0 - 2.8.6, when I run the deserializer on the same code, it will fail with the error below if I use the managed/back reference annotation. When that managed/back annotation is removed, it will run just fine.

com.fasterxml.jackson.databind.JsonMappingException: Invalid definition for property "" (of type Lcom/atribe/reproducingbug/ChildObject;): No non-constructor mutator available
 at [Source: {
  "companyName": "My Famke Company",
  "companyLogoImageId": "29a8045e-3d10-4121-9f27-429aa74d00ad",
  "productId": "ABC-0003",
  "productName": "Engineering Test",
  "recordNumber": "01",
  "revisionNumber": "1.0",
  "procedureId": "6e6f607e-fb3f-4750-8a0a-2b38220e3328",
  "childSet": [
        {
            "title": "Child 1",
            "componentId": "3f7debe1-cddc-4b66-b7a7-49249e0c9d3e",
            "orderLabel": "1",
            "orderNumber": 1
        }
  ]
}; line: 1, column: 1]
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:1329)
    at com.fasterxml.jackson.databind.DeserializationContext.reportBadPropertyDefinition(DeserializationContext.java:1293)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.constructSettableProperty(BeanDeserializerFactory.java:726)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.addReferenceProperties(BeanDeserializerFactory.java:642)
    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:403)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:349)
    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:443)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.createContextual(CollectionDeserializer.java:206)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.createContextual(CollectionDeserializer.java:26)
    at com.fasterxml.jackson.databind.DeserializationContext.handleSecondaryContextualization(DeserializationContext.java:681)
    at com.fasterxml.jackson.databind.DeserializationContext.findContextualValueDeserializer(DeserializationContext.java:445)
    at com.fasterxml.jackson.databind.deser.std.StdDeserializer.findDeserializer(StdDeserializer.java:964)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.resolve(BeanDeserializerBase.java:501)
    at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:293)
    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:476)
    at com.fasterxml.jackson.databind.ObjectReader._findRootDeserializer(ObjectReader.java:1859)
    at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:1621)
    at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1220)
    at com.atribe.reproducingbug.ParentObject.deserialize(ParentObject.java:61)
    at com.atribe.reproducingbug.ParentObjectTest.deserializeTest(ParentObjectTest.java:19)
    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:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    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)
Process finished with exit code -1

From the stacktrace, I found that when it sets up the managed/back references there is this code below in BeanDeserializerFactory.java. The line of interest is when it calls construct in the SimpleBeanPropertyDefinition

protected void addReferenceProperties(DeserializationContext ctxt,
            BeanDescription beanDesc, BeanDeserializerBuilder builder)
        throws JsonMappingException
    {
        // and then back references, not necessarily found as regular properties
        Map<String,AnnotatedMember> refs = beanDesc.findBackReferenceProperties();
        if (refs != null) {
            for (Map.Entry<String, AnnotatedMember> en : refs.entrySet()) {
                String name = en.getKey();
                AnnotatedMember m = en.getValue();
                JavaType type;
                if (m instanceof AnnotatedMethod) {
                    type = ((AnnotatedMethod) m).getParameterType(0);
                } else {
                    type = m.getType();
                }
                SimpleBeanPropertyDefinition propDef = SimpleBeanPropertyDefinition.construct(
                		ctxt.getConfig(), m);
                builder.addBackReferenceProperty(name, constructSettableProperty(ctxt,
                        beanDesc, propDef, type));
            }
        }
    }

The method call has this code from SimpleBeanPropertyDefinition.java, where it calls member.getName():

public static SimpleBeanPropertyDefinition construct(MapperConfig<?> config,
    		AnnotatedMember member) {
        return new SimpleBeanPropertyDefinition(member, PropertyName.construct(member.getName()),
                (config == null) ? null : config.getAnnotationIntrospector(),
                        null, EMPTY_INCLUDE);
    }

member.getName() returns an empty string every single time (that is the current implementation and has been that way for years). Now after this member is instantiated, there is this call where the AnnotatedMember mutator variable is not correctly created:

protected SettableBeanProperty constructSettableProperty(DeserializationContext ctxt,
            BeanDescription beanDesc, BeanPropertyDefinition propDef,
            JavaType propType0)
        throws JsonMappingException
    {
        // need to ensure method is callable (for non-public)
        AnnotatedMember mutator = propDef.getNonConstructorMutator();
        // 08-Sep-2016, tatu: issues like [databind#1342] suggest something fishy
        //   going on; add sanity checks to try to pin down actual problem...
        //   Possibly passing creator parameter?
        if (mutator == null) {
            ctxt.reportBadPropertyDefinition(beanDesc, propDef, "No non-constructor mutator available");
        }
.....omitted rest of method for brevity...

If you go to the method propDef.getNonConstructorMutator(), the implementation is below:

@Override
    public AnnotatedMember getNonConstructorMutator() {
        AnnotatedMember acc = getSetter();
        if (acc == null) {
            acc = getField();
        }
        return acc;
    }

Go to getSetter() and this is the implementation below. The _member variable is always false and returns null.

 @Override
    public AnnotatedMethod getSetter() {
        if ((_member instanceof AnnotatedMethod)
                && ((AnnotatedMethod) _member).getParameterCount() == 1) {
            return (AnnotatedMethod) _member;
        }
        return null;
    }

When we bubble back up to the original caller in constructSettableProperty, it will be null and throw the error even if you explicitly write out a setter method associated with your property that has a managed/back reference.

protected SettableBeanProperty constructSettableProperty(DeserializationContext ctxt,
            BeanDescription beanDesc, BeanPropertyDefinition propDef,
            JavaType propType0)
        throws JsonMappingException
    {
        // need to ensure method is callable (for non-public)
        AnnotatedMember mutator = propDef.getNonConstructorMutator();
        // 08-Sep-2016, tatu: issues like [databind#1342] suggest something fishy
        //   going on; add sanity checks to try to pin down actual problem...
        //   Possibly passing creator parameter?
        if (mutator == null) {
            ctxt.reportBadPropertyDefinition(beanDesc, propDef, "No non-constructor mutator available");
        }
...omitted rest of method for brevity...

[cowtowncoder]

Yes, sounds like a bug. Thank you for thorough investigation and notes.

I haven't had to look into this one but hope to address it.

[sarahlikesglitter]

Thanks for the reply, would greatly appreciate further investigation into this issue and a fix (if any).

[wheredevel]

So, is it a confirmed bug?

[cowtowncoder]

@wheredevel I have not had time to look further, but sounds like legit bug.

[cowtowncoder]

Alas test uses Lombok. This is problematic as I do not have (nor plan to) install Lombok, as it does not (unlike most other libraries) work using just basic build tools and IDE.

[cowtowncoder]

... that aside I do appreciate reproductions, which are greatly appreciated! :-D

[cowtowncoder]

Unfortunately I am unable to reproduce the issue at this point.
When simplifying this to just use fields, default constructor, problem does not occur.
I assume it would be reproducible when Lombok has generated constructors and setters, but I don't have Lombok set up nor plan to do that.

Another thing to know is that @JsonBackReference and @JsonManagedReference can not be passed as Creator (constructor) argument: they must be handled using field or setter.

So, what I would need at this point is reproduction with explicitly defined setters/getters/constructors, with appropriate annotations. I assume Lombok gives access to generated source code, or allows sources to be generated for troubleshooting?
If so, just including data classes ParentObject and ChildObject would be enough

[atribe]

Ok, I'll look at that tomorrow and see if we can reproduce without lombok. Thanks.

[wheredevel]

@cowtowncoder Lombok works with any Java IDE.
For example, in Eclipse:

1. download the jar
2. in eclipse.ini add the line -javaagent:<path to lombok jar>/lombok.jar
3. restart Eclipse

Or follow installation instructions.

One more thing is to include the jar in your build, so that javac would hook it in during your classes compilation (a.k.a. lomboking).
For example, in Maven:

...
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<version>1.16.16</version>
			<scope>provided</scope>
		</dependency>
...

[cowtowncoder]

@wheredevel I know it is possible, but I do not want to install jars for arbitrary frameworks in my classpath. This is why from this point on no Lombok dependencies are to be added for any of Jackson projects: if I did, then everyone everywhere would have to do same installation just to build Jackson.

[atribe]

I tested some different configurations and found that you were correct, the code in my repo works with Lombok removed. So I dug a bit more and found that it only fails when the child is annotated with @AllArgsConstructor. The parent can have it and it works just fine.

I've branched myh repo and changed it so it passes while using lombok. The link shows the specific annotation that is causing the problem.

https://github.com/atribe/ReproducingBug/blob/TestPassesWithLombok/src/main/java/com/atribe/reproducingbug/ChildObject.java

Seems like I probably need to dig a bit more and maybe file a bug with lombok. Thanks for the help.

[cowtowncoder]

@atribe Thank you for digging this up. Just one follow-up question: do you know what @AllArgsConstructor would mean in terms of constructor added? I am not sure if Lombok could be adding Jackson annotations -- would seem unlikely, but on the other hand constructor wouldn't be auto-detected otherwise. Unless you are also using jackson-module-parameter-names with Java 8... which could auto-detect constructor. I am guessing this may be happening.
Note that @AllArgsConstructor itself would have no effect on Jackson: it wouldn't be recognized.
But it would materialize constructor in bytecode, which Jackson would notice.

One other note: code sample is using back references ( @JsonBackReference) which is probably relevant as well. In fact that should not be passed through constructor because it, well, typically can not: it has to point to parent object, which can only be constructed when child object has been instantiated.... so that should remain a separate property (set via setter or field).
I think some earlier versions may have handled things differently by using reverse order.