IncompatibleClassChangeError deserializing interface methods with default impl

[shawnsmith]

With Afterburner I'm getting the exception java.lang.IncompatibleClassChangeError: Found class <MyClass>, but interface was expected trying to deserialize an object where a setter is implemented in an interface.

I've tested with Jackson+Afterburner 2.8.7, 2.8.10 and 2.9.0 and all fail in the same way. (jdk 8)

java.lang.IncompatibleClassChangeError: Found class com.fasterxml.jackson.module.afterburner.deser.TestInterfaceDeser$Model, but interface was expected

	at com.fasterxml.jackson.module.afterburner.deser.TestInterfaceDeser$Model$Access4JacksonDeserializer5b28f286.stringSetter(com/fasterxml/jackson/module/afterburner/deser/TestInterfaceDeser$Model$Access4JacksonDeserializer.java)
	at com.fasterxml.jackson.module.afterburner.deser.SettableStringMethodProperty.deserializeAndSet(SettableStringMethodProperty.java:53)
	at com.fasterxml.jackson.module.afterburner.deser.SuperSonicBeanDeserializer.deserialize(SuperSonicBeanDeserializer.java:159)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2992)
	at com.fasterxml.jackson.module.afterburner.deser.testInterfaceDeserialize(TestInterfaceDeser.java:40)

Here's a test case that reproduces the issue:

package com.fasterxml.jackson.module.afterburner.deser;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.module.afterburner.AfterburnerModule;
import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

public class TestInterfaceDeser {

    public interface Typed {
        String getType();
        default void setType(String type) {
            if (!getType().equals(type)) {
                throw new IllegalStateException(String.format("Expected '%s': %s", getType(), type));
            }
        }
    }

    public static class Model implements Typed {
        @Override
        public String getType() {
            return "Model";
        }
    }

    @Test
    public void testInterfaceDeserialize() throws Exception {
        Model model = new Model();

        ObjectMapper mapper = new ObjectMapper().registerModule(new AfterburnerModule());

        String json = mapper.writeValueAsString(model);
        assertEquals("{\"type\":\"Model\"}", json);

        // Throws: java.lang.IncompatibleClassChangeError: Found class com.fasterxml.jackson.module.afterburner.deser. TestInterfaceDeser$Model, but interface was expected
        Model roundTrip = mapper.readValue(json, Model.class);

        assertNotNull(roundTrip);
    }
}

[cowtowncoder]

Try not using default methods? I can not unfortunately use this reproduction as Jackson 2.x does not require Java 8 and must build on Java 7.

[shawnsmith]

I've worked around it for now by specifying a custom serializer which makes Afterburner skip the property:

@JsonDeserialize(using = PlainStringDeserializer.class)
default void setType(String type) {
   ...
}

and

public static class PlainStringDeserializer extends StdDeserializer<String> {
    public PlainStringDeserializer() {
        super(String.class);
    }

    @Override
    public String deserialize(JsonParser jp, DeserializationContext ctx) throws IOException {
        if (jp.getCurrentToken() != JsonToken.VALUE_STRING) {
            return (String) ctx.handleUnexpectedToken(String.class, jp);
        }
        return jp.getText();
    }
}

Specifying the regular com.fasterxml.jackson.databind.deser.std.StringDeserializer wasn't enough, it looks like it has to be a non-default serializer.

[cowtowncoder]

I think this needs to be tackled via Jackson 3.x version of project, to verify handling of default implementations. But fix itself can I hope be backported in 2.9.x.
I wonder if version of asm library might matter as well; while we are using a relatively recent version maybe we need newer.

[shawnsmith]

It looks like a fix along the following lines might work without requiring an asm upgrade:

In PropertyMutatorCollector.java replace:

boolean isInterface = method.getDeclaringClass().isInterface();
mv.visitMethodInsn(isInterface ? INVOKEINTERFACE : INVOKEVIRTUAL, ...);

with

boolean isInterface = isInterfaceMethod(method);
mv.visitMethodInsn(isInterface ? INVOKEINTERFACE : INVOKEVIRTUAL, ...);

and add

public class DynamicPropertyAccessorBase
{
...
    protected static boolean isInterfaceMethod(Method method) {
        // Forward compatible with Java 8 equivalent: method.getDeclaringClass().isInterface() && !method.isDefault()
        return method.getDeclaringClass().isInterface() &&
                (method.getModifiers() & (Modifier.ABSTRACT | Modifier.PUBLIC | Modifier.STATIC)) != Modifier.PUBLIC;
    }
}

PropertyAccessorCollector.java has a similar but slightly different pattern for calls to visitMethodInsn(), I haven't done any tests to see if it requires the same fix.

The implementation for isInterfaceMethod() above was derived from inlining Method.isDefault() from JDK 8 and simplifying the result.

[cowtowncoder]

Interesting. That could work... Thank you for doing this research; I have been swamped with other things and have limited time to use here, so having a solution speeds fixing up a lot.

But so basically fundamental problem is that although method is defined in an interface, it is "materialized" as regular class method. And certainly seems to be missing ACC_ABSTRACT.
I think that's only thing needed to checked here; static flag should have removed method from being considered already, and I think all methods are public in interfaces.

[cowtowncoder]

Will be fixed in 2.8.11 (if ever released); 2.9.2.

Oddly enough only seems to affect deserialization; serialization seemed ok.
Probably something similar may need to be tackled with mr Bean too.

[shawnsmith]

Awesome, thanks!