Throw error if strings are not double quoted while using jackson objectmapper deserialization

Question

I have a JSON:

{
    "stringField" : 1234,
    "booleanField": true,
    "numberField": 1200.00
}

I use object mapper to deserialize the json into:-

@Data
class SomeClass {
    String stringField;
    boolean booleanField;
    float numberField;
}

I would like the objectMapper to throw an error because, the values for String fields must be double quoted according to the json spec. How can i get objectMapper to throw an error?

Doesn't this throw some error already since this is simply invalid JSON (based on the missing quotes) — luk2302, Sep 28 '20 at 11:35
it's not an invalid json right? Example, boolean values should be without quotes, numbers should be without quotes.. — Jerald Baker, Sep 28 '20 at 11:38
Booleans and numbers (and null) are exactly the two things allowed without quotes, "asdadasd" is not true, false, null or a number -> invalid. Check https://jsonlint.com/ — luk2302, Sep 28 '20 at 11:40
Okay, sorry my bad. I have edited my question. The String field is now 1234. and this must be double quoted as the the field of the POJO is of type String. and i expect objectMapper to throw an error.. can i enforce it? — Jerald Baker, Sep 28 '20 at 11:44
I think this [feature](https://github.com/FasterXML/jackson-databind/issues/2113) is slated be released as part of Jackson 2.12.x. Till it is released, answers on this question should suffice. — Smile, Oct 07 '20 at 11:57

score 1 · Answer 1 · answered Sep 28 '20 at 14:00

You can write custom string deserializer.(i assume you are using spring)

@Configuration
public class JacksonConfiguration {

    @Bean
    SimpleModule jacksonDeserializerConfiguration() {
        SimpleModule module = new SimpleModule();
        module.addDeserializer(String.class, new StdDeserializer<String>(String.class) {
        @Override
        public String deserialize(JsonParser parser, DeserializationContext context)
                throws IOException {
             if (!parser.hasToken(JsonToken.VALUE_STRING)) {
                //throw ex what do u want
                throw new RuntimeException("String not include quote");
            }
            return StringDeserializer.instance.deserialize(parser, context);
        }
    });
        return module;
    }
}

score 0 · Answer 2 · edited Oct 07 '20 at 11:47

This should fix your issue.

class SomeClass {
    @JsonDeserialize(using=ForceStringDeserializer.class)
    public String stringField;
    public boolean booleanField;
    public float numberField;
}


class ForceStringDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
        if (jsonParser.getCurrentToken() != JsonToken.VALUE_STRING) {
            throw deserializationContext.wrongTokenException(jsonParser, JsonToken.VALUE_STRING, "Attempted to parse Integer to String but this is forbidden");
        }
        return jsonParser.getValueAsString();
    }
}

Why it's is down voted ? I have spent hours to figure this and tried at my side before Posting . Its perfectly working solution. — SauriBabu, Oct 06 '20 at 16:23

score 0 · Answer 3 · answered Oct 12 '20 at 17:26

0

You just need to setup jackson objectmapper like this

JsonFactory factory = new JsonFactory();
factory.disable(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES);
ObjectMapper mapper = new ObjectMapper(factory)

This should throw error during serialization/deserilaization

answered Oct 12 '20 at 17:26

Rohitdev

866
6
15

this is field names and not values – Jerald Baker Oct 13 '20 at 08:44

Throw error if strings are not double quoted while using jackson objectmapper deserialization

3 Answers3