Change field case with an ObjectMapper

Question

I think I need to create a specialist ObjectMapper and cannot find any sample code to start the process.

The creator of the JSON is using .Net

Answer 1

Your first issue can be addressed very simply with the @JsonProperty annotation:

// java-side class
public class Facet
{
    @JsonProperty("Name")
    public String name;

    @JsonProperty("Value")
    public String value;
}

Now the ObjectMapper will match up the differently-cased field names. If you don't want to add annotations into your classes, you can create a Mix-in class to stand in for your Facet:

public class FacetMixIn
{
    @JsonProperty("Name")
    public String name;

    @JsonProperty("Value")
    public String value;
}

objectMapper.getDeserializationConfig().addMixInAnnotations(Facet.class, FacetMixIn.class);

This will achieve the same thing, without requiring additional annotations in your Facet class.

Answer 2

This problem could be solved from Jackson 2.5.0 like this:

ObjectMapper mapper = new ObjectMapper();
mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);

From the javadoc:

com.fasterxml.jackson.databind.MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES

Feature that will allow for more forgiving deserialization of incoming JSON. If enabled, the bean properties will be matched using their lower-case equivalents, meaning that any case-combination (incoming and matching names are canonicalized by lower-casing) should work.

Note that there is additional performance overhead since incoming property names need to be lower-cased before comparison, for cases where there are upper-case letters. Overhead for names that are already lower-case should be negligible however.

Feature is disabled by default.

Since: 2.5

Answer 3

Just a quick update as I was looking for same answer and a code snippet objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);

Answer 4

Instead of annotating each field, the Jackson ObjectMapper can be configured to use a built-in or custom PropertyNamingStrategy, to apply a consistent translation between Java property/field names and JSON element names.

For example:

myObjectMapper.setPropertyNamingStrategy(PascalCaseStrategy);