Jackson deserialization convertValue vs readValue

Question

I have a org.json.JSONArray that contains JSONObjects and I am trying to map those to a POJO. I know the type of the POJO I want to map to. I have 2 options and I m trying to figure out which is better in performance.

Option 1:

ObjectMapper mapper = new ObjectMapper();
ObjectReader reader = mapper.reader().withType(MyPojo.class);

for (int i = 0; i < jsonArr.length(); i++) {
    JSONObject obj = jsonArr.getJSONObject(i);
    MyPojo pojo = reader.readValue(obj.toString());

    ... other code dealing with pojo...
}

Option 2:

ObjectReader mapper = new ObjectMapper();

for (int i = 0; i < jsonArr.length(); i++) {
    JSONObject obj = jsonArr.getJSONObject(i);
    MyPojo pojo = mapper.convertvalue(obj, MyPojo.class);

    ... other code dealing with pojo...
}

For sake of argument, lets assume the length of the JSONArray is 100.

From what I have looked so far from the source code, option 1 seems better since the Deserialization context and the Deserializer is created only once, while in case of option 2, it will be done for each call.

Thoughts?

Thanks!

Please fix your second code snippet so that it compiles. I want it to be clear what you are asking about. — Sotirios Delimanolis, Jan 29 '14 at 20:36
Please update this post with your findings so that it helps others. — Srikanth, Sep 12 '14 at 12:48
I have the same dubt as you. I found this on stackOverFlow, might help: http://stackoverflow.com/questions/10113512/readvalue-and-readtree-in-jackson-when-to-use-which — Guerino Rodella, Jun 08 '16 at 01:17
Second snippet could lead to errors as internal structure of `org.json.JSONObject` is not the same as that of a JSON. — aksh1618, Jun 10 '20 at 10:25

score 5 · Answer 1 · answered Aug 02 '21 at 15:07

I will try to explain the difference, with the problem I faced. I used both in a complex conversion I needed to use.

My request was of the format as below.

"{Key=a1, type=ABC}"

I wanted to convert it to some class's (A1) instance.

class A1 {
   private String key;
   private String type;
}

As is clear, the keys are not strings (i.e. not enclosed in double quotes)

With mapper.readValue

I will get error as below:

com.fasterxml.jackson.core.JsonParseException: Unexpected character ('k' (code 115)): was expecting double-quote to start field name

With mapper.convertValue

I will get an instance of A1 as I required.

alphcoder · Answer 2 · 2023-05-05T01:11:55.210

0

Its simple

For converting json string to class type use readValue
For converting object type to class type use convertValue

On printing, object looks like this SampleClass(id=61, applicationReference=AP251, accountId=fghsdjffhhjf)

On printing, jsonString a looks like this {"method":"POST","url"}

edited May 05 '23 at 01:11

answered May 04 '23 at 17:39

alphcoder

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Jackson deserialization convertValue vs readValue

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