Class with cyclic reference and non property id results in NPE

[xardif]

Creating class as below and returning it from an API results in exception (at the bottom of the issue).

@JsonIdentityInfo( generator = ObjectIdGenerators.UUIDGenerator.class )
public class ModelWithJsonIdentityCyclicUUID
{
    public ModelWithJsonIdentityCyclicUUID parent;

}

I have tried using @JsonManagedReference, but this does not result in anything.
The only workaround is to migrate to ObjectIdGenerators.PropertyGenerator and create additional property in model as below:

@JsonIdentityInfo( generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
public class ModelWithJsonIdentityCyclicProperty
{
    public String id;
    public ModelWithJsonIdentityCyclicProperty parent;

}

The above classes can be used to extend test cases in io.swagger.v3.jaxrs2.resources.JsonIdentityCyclicResource.

The exception:

java.lang.NullPointerException
	at io.swagger.v3.core.jackson.ModelResolver$GeneratorWrapper.process(ModelResolver.java:1116)
	at io.swagger.v3.core.jackson.ModelResolver$GeneratorWrapper.access$100(ModelResolver.java:981)
	at io.swagger.v3.core.jackson.ModelResolver$GeneratorWrapper$3.processAsProperty(ModelResolver.java:1051)
	at io.swagger.v3.core.jackson.ModelResolver$GeneratorWrapper.processJsonIdentity(ModelResolver.java:1098)
	at io.swagger.v3.core.jackson.ModelResolver.resolve(ModelResolver.java:295)
	at io.swagger.v3.core.converter.ModelConverterContextImpl.resolve(ModelConverterContextImpl.java:90)
	at io.swagger.v3.core.converter.ModelConverters.resolveAsResolvedSchema(ModelConverters.java:112)
	at io.swagger.v3.core.util.ParameterProcessor.applyAnnotations(ParameterProcessor.java:62)
	at io.swagger.v3.jaxrs2.DefaultParameterExtension.extractParameters(DefaultParameterExtension.java:116)
	at io.swagger.v3.jaxrs2.Reader.getParameters(Reader.java:1282)
	at io.swagger.v3.jaxrs2.Reader.read(Reader.java:514)
	at io.swagger.v3.jaxrs2.Reader.read(Reader.java:121)
	at io.swagger.v3.jaxrs2.JsonIdentityTest.testJsonIdentityCyclic(JsonIdentityTest.java:23)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:124)
	at org.testng.internal.Invoker.invokeMethod(Invoker.java:580)
	at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:716)
	at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:988)
	at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
	at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
	at org.testng.TestRunner.privateRun(TestRunner.java:648)
	at org.testng.TestRunner.run(TestRunner.java:505)
	at org.testng.SuiteRunner.runTest(SuiteRunner.java:455)
	at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:450)
	at org.testng.SuiteRunner.privateRun(SuiteRunner.java:415)
	at org.testng.SuiteRunner.run(SuiteRunner.java:364)
	at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
	at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:84)
	at org.testng.TestNG.runSuitesSequentially(TestNG.java:1208)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1137)
	at org.testng.TestNG.runSuites(TestNG.java:1049)
	at org.testng.TestNG.run(TestNG.java:1017)
	at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:66)
	at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:110)

[xardif]

There is also another workaround - using com.fasterxml.jackson.annotation.ObjectIdGenerators.StringIdGenerator somehow bypasses mechanism that causes exception and works flawlessly.

So the sample class looks as below:

@JsonIdentityInfo( generator = ObjectIdGenerators.StringIdGenerator.class )
public class ModelWithJsonIdentityCyclicUUIDString
{
    public ModelWithJsonIdentityCyclicUUIDString parent;

}

[daniel-schel]

I have created a fix for this issue in the following PR: #3908

Unfortunately, I had found this issue later and also opened my own: #3907

[daniel-schel]

@xardif: The ObjectIdGenerators.StringIdGenerator works, because it is not taken into consideration yet, which is another bug from my point of view.

[frantuma]

Closing as fixed by #3908