Parse JSON array with jackson where objects are strings?

Question

I have a slightly odd question. I have created an object, let's call it a Profile, that successfully parses single JSON objects via an API that I call. There is also a multi-profile interface that will return a JSON array of Profile objects. The problem is, the multi-profile interface turns the sub objects into strings. Is there an automatic way I can tell jackson to parse these into objects?

Example of a single object: { "foo": "bar" }

Example of a multi object: [ "{ \"foo\": \"bar\" }", "{ \"blah\": \"ugh\" }" ]

(Sorry can't use real data)

Notice that the sub objects are actually strings, with escaped quotes inside them.

For completeness, my code for the multi object parse looks like this:

ObjectMapper mapper = new ObjectMapper();
Profile[] profile_array = mapper.readValue(response.content, Profile[].class);
for (Profile p: profile_array)
{
    String user = p.did;
    profiles.put(user, p);
}

As I said, in the single-profile case, the Profile object parses. In the multi-profile case, I get this exception:

Exception: org.codehaus.jackson.map.JsonMappingException: Can not construct instance of com.xyz.id.profile.Profile, problem: no suitable creator method found to deserialize from JSON String

Is Profile a class or an interface? Why not just implement fromValue(String) on it and place the parse logic in there? — Perception
– Perception, Commented Jun 12, 2012 at 0:56
Profile is a class which is a container for the JSON profile object data. — Need4Speed
– Need4Speed, Commented Jun 12, 2012 at 18:10

Crozin · Accepted Answer · 2012-06-12 00:09:34Z

2

I suppose you'll have to create a custom deserializer and apply it to the every element of that array.

class MyCustomDeserializer extends JsonDeserializer<Profile> {
    private static ObjectMapper om = new ObjectMapper();

    @Override
    public Profile deserialize(JsonParser jp, DeserializationContext ctxt) {
        // this method is responsible for changing a single text node:
        // "{ \"foo\": \"bar\" }"
        // Into a Profile object

        return om.readValue(jp.getText(), Profile.class);
    }
}

answered Jun 12, 2012 at 0:09

Crozin

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1 Comment

Need4Speed Over a year ago

I was afraid that was the answer. I'll give it a try, thanks.

StaxMan · Accepted Answer · 2012-06-12 18:13:22Z

0

There is no out-of-the-box support for "re-parsing" of embedded JSON-in-JSON content. But this sounds like a possible request for enhancement (RFE)...

answered Jun 12, 2012 at 18:13

StaxMan

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Comments

Faraday · Accepted Answer · 2012-06-12 18:59:43Z

0

Have you tried using JAXB?

            final ObjectMapper mapper = new ObjectMapper();

            // Setting up support of JAXB
            final AnnotationIntrospector introspector = new JaxbAnnotationIntrospector();

            // make deserializer use JAXB annotations (only)
            mapper.getDeserializationConfig().setAnnotationIntrospector(
                    introspector);

            // make serializer use JAXB annotations (only)
            mapper.getSerializationConfig().setAnnotationIntrospector(
                    introspector);

            final StringReader stringReader = new StringReader(response);
            respGetClasses = mapper.readValue(stringReader,
                    FooBarClass.class);

The above should get you started...

Also, you would need to mark each subclass like so:

@XmlElement(name = "event")
public List<Event> getEvents()
{
    return this.events;
}

edited Jun 12, 2012 at 18:59

answered Jun 12, 2012 at 0:07

Faraday

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4 Comments

StaxMan Over a year ago

While one can use JAXB annotations this way, how would this help with the actual issue at hand?

Faraday Over a year ago

@StaxMan his issue is that he wants to force the parsing of JSON into complex objects and he is having issues. I'm just putting forward my solution (using JAXB), as I have used it to solve issues like his when I was using the Jackson lib...

StaxMan Over a year ago

Actually I don't think his problem is really that: if you look carefully at JSON sample he is showing, the multi-object case, there is the bigger issue of content being a String, not JSON. But even if it was JSON, there would be structural difference between arrays and objects. This is why I asked: you are showing how to specify property names, which can be useful, but it does not seem to be something submitter is struggling with. So I thought maybe I was missing something here....

Faraday Over a year ago

@StaxMan - ahhhh, my mistake. Although he is asking how to prevent them from becoming strings, which my solution would help with. Basically he has normal JSON, once he's passed it through his 'multi-profile interface' they are returned as strings rather than objects. I'm approaching this with a view to fix his 'multi-profile interface' rather than parse the strings into an object. But perhaps I'm not understanding the OP correctly, it's happened before, and it'll happen again! :)

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