Handling N / A as Null with Jackson
I am receiving data from external JSON API and parse the result using Jackson. Unfortunately, this API returns all fields as String
, and they are populated with "N/A"
when no data is available.
I would like to replace those fields null
, especially since it is frustrating when I am trying to convert JSON String fields to more informative Java fields.
Custom DeserializationProblemHandler
worked for fields Integer
(see below), but it was not used for Java 8 fields LocalDate
. In addition, he reacts to the problem, rather than anticipating it.
I was unable to find a pre-processor to set up in mine ObjectMapper
and am embarrassed with the idea of overriding BeanDeserializer
.
Do you know the best / cleanest solution for dealing with situations like this? Thank!
DeserializationProblemHandler
new DeserializationProblemHandler() {
@Override
public Object handleWeirdStringValue(DeserializationContext ctxt, Class<?> targetType, String valueToConvert, String failureMsg) throws IOException {
return "N/A".equals(valueToConvert) ? null : super.handleWeirdStringValue(ctxt, targetType, valueToConvert, failureMsg);
}
}
Error message while processing "N/A"
in the fieldLocalDate
Can not deserialize value of type java.time.LocalDate from String "N/A": Text 'N/A' could not be parsed at index 0
(works great when there is a date in the data)
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I feel like there must be a better way to do this, but the following is the only solution I could come up with.
Create a new JsonDeserializer
one that handles the "N / A" input. The following example processes strings:
public class EmptyStringDeserializer extends StdScalarDeserializer<String> {
public EmptyStringDeserializer() {
super(String.class);
}
@Override
public String deserialize(JsonParser parser, DeserializationContext ctx) throws IOException {
final String val = parser.getValueAsString();
if ("N/A".equalsIgnoreCase(val))
return null;
return val;
}
}
The class is registered with the ObjectMapper
following:
SimpleModule simpleModule = new SimpleModule().addDeserializer(String.class, new EmptyStringDeserializer());
ObjectMapper om = new ObjectMapper().registerModule(simpleModule);
You probably want to bundle all of your converters into a module named API that forces you to handle things like this.
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