Jackson ObjectMapper upper/lower case issues

I've had the same problem.

This is my solution:

public class MyNamingStrategy extends PropertyNamingStrategy {

    @Override
    public String nameForField(MapperConfig<?> config, AnnotatedField field, String defaultName) {
        return field.getName();
    }

    @Override
    public String nameForGetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) {
        return convert(method, defaultName);
    }

    @Override
    public String nameForSetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) {
        return convert(method, defaultName);
    }

    private String convert(AnnotatedMethod method, String defaultName) {

        Class<?> clazz = method.getDeclaringClass();
        List<Field> flds = FieldUtils.getAllFieldsList(clazz);
        for (Field fld : flds) {
            if (fld.getName().equalsIgnoreCase(defaultName)) {
                return fld.getName();
            }
        }

        return defaultName;
    }
}

In this case you will get the exact name of the property, and will not have to depend on the correct names of the methods.

I think that this is the solution (using custom PropertyNamingStrategy):

import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.cfg.MapperConfig;
import com.fasterxml.jackson.databind.introspect.AnnotatedField;
import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;

public class MyPropertyNamingStrategy extends PropertyNamingStrategy {
    @Override
    public String nameForField(MapperConfig<?> config, AnnotatedField field, String defaultName) {
        return convert(field.getName());
    }

    @Override
    public String nameForGetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) {
        return convert(method.getName().toString());
    }

    @Override
    public String nameForSetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) {
        return convert(method.getName().toString());
    }

    private String convert(String input) {
        return input.substring(3);
    }
}

Test

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.io.IOException;
import java.io.StringWriter;

public class MyPropertyNamingStrategyTest {
    public static void main(String[] args) {
        PrivatePerson privatePerson = new PrivatePerson();
        privatePerson.setFirstName("John");
        privatePerson.setLastName("Smith");

        ObjectMapper mapper = new ObjectMapper();
        mapper.setPropertyNamingStrategy(new MyPropertyNamingStrategy());
        mapper.enable(SerializationFeature.INDENT_OUTPUT);
        StringWriter sw = new StringWriter();
        try {
            mapper.writeValue(sw, privatePerson);
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(sw.toString());
    }
}

PrivatePerson

public class PrivatePerson {
    private String firstName;
    private String lastName;

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getLastName() {
        return lastName;
    }
}

Even though @JsonProperty doesn't work, I was able to use @JsonSetter and @JsonGetter to map capitalized json field names.

@JsonSetter("ABC")
public void setABC(String ABC) {
    this.ABC= ABC;
}

Spring will now serialize the object field as "ABC" and not "abc".

You can configure Jackson to be case sensitivity tolerant:

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

Cudos to https://stackoverflow.com/a/32842962/1639556