Exception deserializing a byte[] when the target type comes from an annotation

[gmjabs]

When trying to deserialize a byte[] from a Map when the deserialization type comes from an annotation, I'm seeing the following exception:

java.lang.IllegalArgumentException: Can not deserialize Class [B (of type array) as a Bean
        at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.isPotentialBeanType(BeanDeserializerFactory.java:808)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.createBeanDeserializer(BeanDeserializerFactory.java:138)
        at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer2(DeserializerCache.java:403)
        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:428)
        at com.fasterxml.jackson.databind.deser.std.StdDeserializer.findDeserializer(StdDeserializer.java:947)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.resolve(BeanDeserializerBase.java:439)
        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:461)
        at com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:3804)
        at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:3418)
        at com.fasterxml.jackson.databind.ObjectMapper.convertValue(ObjectMapper.java:3351)

The below is a repro.

public class JacksonTest {

    static class Foo {
        @JsonProperty
        @JsonDeserialize(as=byte[].class)
        Object someBytes;
    }

    public void testFooFromMap() {

        Map<String, Object> map = new HashMap<>();
        map.put("someBytes", "HelloWorld".getBytes());

        ObjectMapper m = new ObjectMapper();
        m.convertValue(map, Foo.class);
    }
}

I discovered this on 2.5.1, but I tried 2.6.0 and it's exhibiting the same behavior.

Thanks!

[cowtowncoder]

Interesting. I suspect this has to do with the way type overrides are passed, and the fact that JavaType for byte[] is an ArrayType. Looks like I can reproduce this without conversion, with plain deserialization.

[gmjabs]

Yeah, it looks like when BasicDeserializer.modifyTypeByAnnotation() is called for the annotated field, it updates the field's JavaType (a SimpleType of Object.class) using narrowBy().

But SimpleType.narrowBy(byte[].class) just creates a new SimpleType of the subclass, in this case a SimpleType of byte[].class, when it should probably be returning the appropriate ArrayType.

[cowtowncoder]

Right, the problem is that JavaType really has no way to change itself appropriately. But TypeFactory had constructSpecializedType() added at some point during 2.x, which was added to basically replace JavaType.narrowBy(). It is not perfect, but handles this particular case properly.

[gmjabs]

Thanks for the quick fix!

[cowtowncoder]

np, thank you for reporting! Surprising no one had encountered this before.
Fix is in 2.6.1, which was released last night.