ObjectMapper using com.jsoniter library

Question

I have a Map<String, Object> map that was deserialized from a simple JSON string {"field1":"val1", "field2":"val2", "isReal":true}. I am trying to construct a Java object MyObject with the above fields.

I can do it using com.fasterxml.jackson.databind.ObjectMapper like so:

public static MyObject load(Map<String, Object> map) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(new ObjectMapper().writeValueAsString(map), MyObject.class);
    }

I was wondering if anyone knows how to do the same using com.jsoniter library?

I have tried to use JsonIterator.deserialize, but that doesn't take a Map as input.

I have also seen ReflectionEncoderFactory usage on the library website, but I don't fully grasp as to how I would use it to construct an object MyObject

@ScaryWombat I don't know what API to use to convert `Map map` to POJO using `com.jsoniter`. I know that `ObjectMapper` from `jackson.databind.ObjectMapper` works, but what would be the equivalent using `jsoniter` library? — QuirkyBit, Jan 07 '20 at 01:27
Did you look at http://jsoniter.com/ ? On the front page they have examples using `deserialize` - did you try this? — Scary Wombat, Jan 07 '20 at 01:31
@ScaryWombat, I did, I don't understand how to use it... can you please explain? — QuirkyBit, Jan 07 '20 at 01:56
why don't you post what you have tried? It looks very similar in concept to jackson — Scary Wombat, Jan 07 '20 at 02:03
@ScaryWombat I only see how to `deserialize` a JSON string or bytes[] to an object or Iterator, I would like to `deserialize` a map to an object of class `MyObject`. I don't see a `deserialize` methods that takes a `Map map` as input. — QuirkyBit, Jan 07 '20 at 02:06
@ScaryWombat I've updated the question to say what I have tried, but I must be not understanding the examples at jsoniter.com because I wasn't able to construct an object like I can with jackson. — QuirkyBit, Jan 07 '20 at 02:11
See this [answer](https://stackoverflow.com/a/36934134/2310289) Basically uou are wanting to convert a map to json with no dependancies (otherwise use jackson) — Scary Wombat, Jan 07 '20 at 02:24
@ScaryWombat I can convert it without dependencies, and I also know how to do it with jackson. My questions are: 1) Is it possible to do it with jsoniter? 2) How? Any help would be appreciated. Thank you! — QuirkyBit, Jan 07 '20 at 02:29
@ScaryWombat I am also NOT trying to get a JSON string back, I am trying to map a `Map map` to an object using jsoniter library. — QuirkyBit, Jan 07 '20 at 02:31
Is not the intermediate step `new ObjectMapper().writeValueAsString(map)` converting to json? Once you have json you can use jsoniter to `deserialize` to your object - no? Anyway, that is all I can add. — Scary Wombat, Jan 07 '20 at 02:37
The equivalent would be: `public static PulsarS3SourceConfig load(Map map) throws IOException { JsonStream.serialize(map); return JsonIterator.deserialize(JsonStream.serialize(map), PulsarS3SourceConfig.class); }` — QuirkyBit, Jan 07 '20 at 02:51
@ScaryWombat I don't need it twice, it was a typo. Yes, you have set me in the right direction. — QuirkyBit, Jan 07 '20 at 02:59

score 4 · Accepted Answer · answered Jan 07 '20 at 02:57

As per @Scary Wombat's explanation:

First it is necessary to convert the Map back to JSON string and then convert the JSON string to an object:

    public static MyObject load(Map<String, Object> map) throws IOException {
        return JsonIterator.deserialize(JsonStream.serialize(map), MyObject.class);
    }

JsonStream.serialize(map) is the same new ObjectMapper().writeValueAsString(map)

ObjectMapper using com.jsoniter library

1 Answers1