Deserialization from "{}" to ObjectNode field causes "out of END_OBJECT token" error

[frsyuki]

I found that deserializing from an empty object ({}) to ObjectNode field in a class field fails.

Here is the minimum code to reproduce:

public class Main
{
    public static class MyValue
    {
        private final ObjectNode object;

        @JsonCreator
        public MyValue(ObjectNode object) { this.object = object; }

        @JsonValue
        public ObjectNode getObject() { return object; }
    }

    public static void main(String[] args)
            throws Exception
    {
        ObjectMapper om = new ObjectMapper();

        ObjectNode object = new ObjectNode(JsonNodeFactory.instance);

        String json = om.writeValueAsString(object);
        System.out.println("json: "+json);

        ObjectNode de1 = om.readValue(json, ObjectNode.class);  // this works
        System.out.println("Deserialized to ObjectNode: "+de1);

        MyValue de2 = om.readValue(json, MyValue.class);  // but this throws exception
        System.out.println("Deserialized to MyValue: "+de2);
    }
}

Result is:

json: {}
Deserialized to ObjectNode: {}
Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.fasterxml.jackson.databind.node.ObjectNode out of END_OBJECT token
 at [Source: {}; line: 1, column: 2]
        at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
        at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:854)
        at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:850)
        at com.fasterxml.jackson.databind.deser.std.JsonNodeDeserializer$ObjectDeserializer.deserialize(JsonNodeDeserializer.java:104)
        at com.fasterxml.jackson.databind.deser.std.JsonNodeDeserializer$ObjectDeserializer.deserialize(JsonNodeDeserializer.java:83)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1095)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:294)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:131)
        at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3731)
        at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2724)
        at Main.main(Main.java:35)

If the object is not empty (e.g. {"k":"v"}), it works:

        ...
        ObjectNode object = new ObjectNode(JsonNodeFactory.instance);
        object.put("k", "v");  // added
        ...

json: {"k":"v"}
Deserialized to ObjectNode: {"k":"v"}
Deserialized to MyValue: io.digdag.cli.Main$MyValue@17550481

Environment:

• jackson-core 2.6.2
• jackson-databind 2.6.2
• Java 8 (Java(TM) SE Runtime Environment (build 1.8.0_20-b26))

[cowtowncoder]

Interesting. Thank you for reporting this, will try to fix it.

[cowtowncoder]

Ok. This is due to a lesser-known aspect of deserialization of JSON Objects; parser may be positioned over first content token, and this in turn may actually be END_OBJECT. Fixed ObjectNode deserializer to handle that correctly.