`JacksonBlackbirdAccess` Class access exception with Groovy Script Serialization using `BlackbirdModule` #285

apoorvam · 2025-02-17T19:03:14Z

I'm encountering an issue when attempting to use the BlackbirdModule in a Spring Boot 3.2 application with Groovy scripting. The goal is to serialize a Groovy object into JSON using the Jackson ObjectMapper with the BlackbirdModule. However, the test case below fails with an exception during the serialization of a Groovy object.

 @Test
    void testGroovySerializationWithBlackbird() throws Exception {
        // Define a Groovy script as a String
        String script = """
                    import com.fasterxml.jackson.databind.ObjectMapper
                    import com.fasterxml.jackson.module.blackbird.BlackbirdModule

                    class Person {
                        String name
                        int age
                    }

                    def mapper = new ObjectMapper()
                    mapper.registerModule(new BlackbirdModule())

                    def person = new Person(name: "Groovy User", age: 35)
                    def json = mapper.writeValueAsString(person)

                    return json // Returning the JSON string
                """;

        // Execute the Groovy script
        GroovyShell shell = new GroovyShell();
        Object result = shell.evaluate(script);

        assertNotNull(result);
    }

Exception:

java.lang.ClassFormatError: Illegal class name "/$$JacksonBlackbirdAccess" in class file /$$JacksonBlackbirdAccess
	at java.base/java.lang.ClassLoader.defineClass0(Native Method)
	at java.base/java.lang.System$2.defineClass(System.java:2394)
	at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2505)
	at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2480)
	at java.base/java.lang.invoke.MethodHandles$Lookup.defineClass(MethodHandles.java:1865)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.accessClassIn(CrossLoaderAccess.java:131)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.grantAccess(CrossLoaderAccess.java:94)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.apply(CrossLoaderAccess.java:83)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.apply(CrossLoaderAccess.java:11)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.createProperty(BBSerializerModifier.java:109)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.lambda$findProperties$0(BBSerializerModifier.java:67)
	at com.fasterxml.jackson.module.blackbird.util.Unchecked.lambda$runnable$0(Unchecked.java:31)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.findProperties(BBSerializerModifier.java:68)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.changeProperties(BBSerializerModifier.java:52)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.constructBeanOrAddOnSerializer(BeanSerializerFactory.java:415)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.findBeanOrAddOnSerializer(BeanSerializerFactory.java:295)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory._createSerializer2(BeanSerializerFactory.java:240)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.createSerializer(BeanSerializerFactory.java:174)
	at com.fasterxml.jackson.databind.SerializerProvider._createUntypedSerializer(SerializerProvider.java:1503)
	at com.fasterxml.jackson.databind.SerializerProvider._createAndCacheUntypedSerializer(SerializerProvider.java:1451)
	at com.fasterxml.jackson.databind.SerializerProvider.findValueSerializer(SerializerProvider.java:556)
	at com.fasterxml.jackson.databind.SerializerProvider.findTypedValueSerializer(SerializerProvider.java:834)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:307)
	at com.fasterxml.jackson.databind.ObjectMapper._writeValueAndClose(ObjectMapper.java:4719)
	at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3964)
	at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:321)
	at Script1.run(Script1.groovy:13)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:460)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:495)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:469)
	at JacksonBlackbirdTest.testGroovySerializationWithBlackbird(JacksonBlackbirdTest.java:100)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

I am using jackson-bom version 2.15.4 and Groovy 4.0.17 that's default with Spring Boot 3.2. Any suggestions? Removing Blackbird module in above test passes, works even with afterburner module. Just not with blackbird module.

The text was updated successfully, but these errors were encountered:

apoorvam · 2025-02-21T14:31:20Z

Hi, would like to know if there are any workarounds for this. Any suggestions?

cowtowncoder · 2025-02-25T03:21:21Z

My main suggestion would be to try a more recent version -- ideally 2.18.2 -- of Jackson components.
There are occasionally fixes to Blackbird and this would rule out possibility later version works better.

Otherwise I suspect Groovy-generated class has name that somehow Blackbird has issues with. Perhaps it is in the "default package" (i.e. one without name) and BB does not handle that case well.

@stevenschlansker WDYT?

apoorvam · 2025-02-25T04:30:32Z

I tried with 2.18.2 and see the same error unfortunately.

java.lang.ClassFormatError: Illegal class name "/$$JacksonBlackbirdAccess" in class file /$$JacksonBlackbirdAccess
	at java.base/java.lang.ClassLoader.defineClass0(Native Method)
	at java.base/java.lang.System$2.defineClass(System.java:2394)
	at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2505)
	at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2480)
	at java.base/java.lang.invoke.MethodHandles$Lookup.defineClass(MethodHandles.java:1865)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.accessClassIn(CrossLoaderAccess.java:131)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.grantAccess(CrossLoaderAccess.java:94)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.apply(CrossLoaderAccess.java:83)
	at com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.apply(CrossLoaderAccess.java:11)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.createProperty(BBSerializerModifier.java:111)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.lambda$findProperties$0(BBSerializerModifier.java:69)
	at com.fasterxml.jackson.module.blackbird.util.Unchecked.lambda$runnable$0(Unchecked.java:31)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.findProperties(BBSerializerModifier.java:70)
	at com.fasterxml.jackson.module.blackbird.ser.BBSerializerModifier.changeProperties(BBSerializerModifier.java:54)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.constructBeanOrAddOnSerializer(BeanSerializerFactory.java:415)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.findBeanOrAddOnSerializer(BeanSerializerFactory.java:295)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory._createSerializer2(BeanSerializerFactory.java:240)
	at com.fasterxml.jackson.databind.ser.BeanSerializerFactory.createSerializer(BeanSerializerFactory.java:174)
	at com.fasterxml.jackson.databind.SerializerProvider._createUntypedSerializer(SerializerProvider.java:1523)
	at com.fasterxml.jackson.databind.SerializerProvider._createAndCacheUntypedSerializer(SerializerProvider.java:1471)
	at com.fasterxml.jackson.databind.SerializerProvider.findValueSerializer(SerializerProvider.java:578)
	at com.fasterxml.jackson.databind.SerializerProvider.findTypedValueSerializer(SerializerProvider.java:856)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:330)
	at com.fasterxml.jackson.databind.ObjectMapper._writeValueAndClose(ObjectMapper.java:4811)
	at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:4052)
	at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:321)
	at Script1.run(Script1.groovy:13)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:460)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:495)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:469)

@cowtowncoder How can I inspect this Groovy generated class to root cause this?

cowtowncoder · 2025-02-25T16:24:26Z

To be honest, I don't know. Maybe debugging on com.fasterxml.jackson.module.blackbird.CrossLoaderAccess.accessClassIn would show name of dynamic class being generated?

apoorvam · 2025-03-06T04:08:52Z

@cowtowncoder Debugging accessClassIn method,

accessClassName = ".$$JacksonBlackbirdAccess"
fqcn = "/$$JacksonBlackbirdAccess"
and finally throws a ClassFormatError: java.lang.ClassFormatError: Illegal class name "/$$JacksonBlackbirdAccess" in class file /$$JacksonBlackbirdAccess at line:
return (Class<?>) DEFINE_CLASS.invokeExact(lookup, classBytes.toByteArray());

What made my test pass is adding a package name at beginning of script

    @Test
    void testGroovySerializationWithBlackbird() throws Exception {
        // Define a Groovy script as a String
        String script = """
                    package abc;
                    import com.fasterxml.jackson.databind.ObjectMapper
                    import com.fasterxml.jackson.module.blackbird.BlackbirdModule

                    class Person {
                        String name
                        int age
                    }

                    def mapper = new ObjectMapper()
                    mapper.registerModule(new BlackbirdModule())

                    def person = new Person(name: "Groovy User", age: 35)
                    def json = mapper.writeValueAsString(person)

                    return json // Returning the JSON string
                """;

        // Execute the Groovy script
        GroovyShell shell = new GroovyShell();
        Object result = shell.evaluate(script);

        assertNotNull(result);
    }

While i couldn't test this exactly, i think handling case where pkg.getName() is empty in accessClassIn method would fix this.

            String fqcn = pkg.getName()
                    .replace('.', '/')
                + "/" + CLASS_NAME;

to

String fqcn = (pkg.getName().isEmpty() ? "" : pkg.getName().replace('.', '/') + "/") + CLASS_NAME;

cowtowncoder · 2025-03-06T04:14:24Z

@apoorvam Thank you for sharing! This should help resolve the issue -- main challenge is probably just adding a test to verify (ideally not adding Groovy dependency even just for tests). Might work with just root-level test class -- or maybe using JDK script support.

That is: I think your fix would probably work, but we'd need a verification of some kind to prove it (and guard against regression).

apoorvam · 2025-03-06T04:18:47Z

    public static class Dummy {
    }

    @Test
    public void testAccessClassInDefaultPackage() throws Exception {
        MethodHandles.Lookup lookup = MethodHandles.lookup().in(Dummy.class);
        
        Class<?> accessClass = CrossLoaderAccess.accessClassIn(lookup);
        
        assertNotNull(accessClass);
        assertEquals("$$JacksonBlackbirdAccess", accessClass.getSimpleName());
    }

@cowtowncoder Something like this? I'll have to test it though. I couldn't test it because CrossLoaderAccess class isn't exposed externally

cowtowncoder · 2025-03-06T04:32:19Z

I was thinking more an actual end-to-end test of serializing/deserializing root-level value class. Sort of reproducing your actual use case wrt value class not being in any package.

apoorvam · 2025-03-07T04:04:29Z

Is there a CI pipeline that i can run my test on? #289 @cowtowncoder

stevenschlansker · 2025-03-07T17:33:10Z

Thanks for tracking this down, I did not consider the default package when writing this, I agree that is likely the problem.

cowtowncoder · 2025-03-07T18:41:18Z

@apoorvam I had to approve running of CI since you're new contributor.

apoorvam · 2025-03-08T05:01:27Z

@cowtowncoder When will 2.19 be released? Also, amended a change: #292

cowtowncoder · 2025-03-08T19:07:36Z

@apoorvam With all the work for 3.0.0-rc1 (just released), it may take a while. No firm plans.

Then again it might be time to consider 2.19.0-rc1 to get 2.19.0 out of the way.

So... I don't know :)

Thanks for follow up wrt #292.

apoorvam · 2025-03-10T13:08:50Z

Looking forward for v2.19.0 with this fix! Thank you.

cowtowncoder added the blackbird Issue related to Blackbird module label Feb 25, 2025

apoorvam added a commit to apoorvam/jackson-modules-base that referenced this issue Mar 7, 2025

Add test to reproduce FasterXML#285

d0d9936

cowtowncoder changed the title ~~JacksonBlackbirdAccess Class access exception with Groovy Script Serialization Using BlackbirdModule~~ JacksonBlackbirdAccess Class access exception with Groovy Script Serialization using BlackbirdModule Mar 8, 2025

cowtowncoder pushed a commit that referenced this issue Mar 8, 2025

Add test to reproduce #285 (#289)

cae0fce

apoorvam pushed a commit to apoorvam/jackson-modules-base that referenced this issue Mar 8, 2025

FasterXML#285 Remove package name

41dee35

cowtowncoder pushed a commit that referenced this issue Mar 8, 2025

Fix to #285 Remove package name (#292)

cf79d8e

apoorvam closed this as completed Mar 10, 2025

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`JacksonBlackbirdAccess` Class access exception with Groovy Script Serialization using `BlackbirdModule` #285

`JacksonBlackbirdAccess` Class access exception with Groovy Script Serialization using `BlackbirdModule` #285

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JacksonBlackbirdAccess Class access exception with Groovy Script Serialization using BlackbirdModule #285

JacksonBlackbirdAccess Class access exception with Groovy Script Serialization using BlackbirdModule #285

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`JacksonBlackbirdAccess` Class access exception with Groovy Script Serialization using `BlackbirdModule` #285

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