Ignoring new fields on JSON objects using Jackson
I'm using Jackson JSON library to convert some JSON objects to POJO classes on an android application. The problem is, the JSON objects might change and have new fields added while the application is published, but currently it will break even when a simple String field is added, which can safely be ignored.
Is there any way to tell Jackson to ignore newly added fields? (eg non-existing on the POJO objects)? A global ignore would be great.
Jackson provides an annotation that can be used on class level (JsonIgnoreProperties).
Add the following to the top of your class (not to individual methods):
@JsonIgnoreProperties(ignoreUnknown = true)
public class Foo {
...
}
Depending on the jackson version you are using you would have to use a different import in the current version it is:
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
in older versions it has been:
import org.codehaus.jackson.annotate.JsonIgnoreProperties;
In addition two 2 mechanisms already mentioned, there is also global feature that can be used to suppress all failures caused by unknown (unmapped) properties:
// jackson 1.9 and before
objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
// or jackson 2.0
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
This is the default used in absence of annotations, and can be convenient fallback.
Up to date and complete answer with Jackson 2
Using Annotation
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
@JsonIgnoreProperties(ignoreUnknown = true)
public class MyMappingClass {
}
See JsonIgnoreProperties on Jackson online documentation.
Using Configuration
Less intrusive than annotation.
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
ObjectReader objectReader = objectMapper.reader(MyMappingClass.class);
MyMappingClass myMappingClass = objectReader.readValue(json);
See FAIL_ON_UNKNOWN_PROPERTIES on Jackson online documentation.
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