Upper / Lower Case Issues Jackson ObjectMapper

Question

When I serialize / deserialize any object, all field names are converted to lowercase. Is there any configuration that forces Jackson to save field names exactly as they are? Both for serialization and for deserialization?

(I know about @JsonProperty, but that doesn't seem right, as I only need Jackson to respect what already exists)

My test code is:

import java.io.Serializable; import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.PropertyNamingStrategy; import com.fasterxml.jackson.databind.SerializationFeature; import com.fasterxml.jackson.databind.cfg.MapperConfig; import com.fasterxml.jackson.databind.introspect.AnnotatedField; import com.fasterxml.jackson.databind.introspect.AnnotatedMethod; public class Test { static class Example implements Serializable { private String Test; private String ABC; private String XyZ; public String getTest() { return Test; } public void setTest(String test) { Test = test; } public String getABC() { return ABC; } public void setABC(String abc) { ABC = abc; } public String getXyZ() { return XyZ; } public void setXyZ(String xyz) { XyZ = xyz; } } static class MyPropertyNamingStrategy extends PropertyNamingStrategy { @Override public String nameForField(MapperConfig<?> config, AnnotatedField field, String defaultName) { return convert(defaultName); } @Override public String nameForGetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) { return convert(defaultName); } @Override public String nameForSetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) { return convert(defaultName); } private String convert(String input) { return input; } } public static void main(String[] args) throws Exception { ObjectMapper objectMapper = new ObjectMapper() .setPropertyNamingStrategy(new MyPropertyNamingStrategy()) .enable(SerializationFeature.INDENT_OUTPUT) .configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true); //From OBJECT to JSON Example ex = new Example(); ex.setTest("1"); ex.setABC("2"); ex.setXyZ("3"); System.out.println(objectMapper.writeValueAsString(ex)); //FROM JSON to OBJECT String jsonString = "{ \"Test\":\"0\", \"ABC\":\"1\", \"XyZ\":\"2\" }"; Example fEx = objectMapper.readValue(jsonString, Example.class); } } 

Thanks to @ BlueLettuce16, I was able to create an “improved” version of PropertyNamingStrategy . There he is:

 import java.lang.reflect.Modifier; 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 CustomPropertyNamingStrategy extends PropertyNamingStrategy { @Override public String nameForField(MapperConfig<?> config, AnnotatedField field, String defaultName) { return convertForField(defaultName); } @Override public String nameForGetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) { return convertForMethod(method, defaultName); } @Override public String nameForSetterMethod(MapperConfig<?> config, AnnotatedMethod method, String defaultName) { return convertForMethod(method, defaultName); } private String convertForField(String defaultName) { return defaultName; } private String convertForMethod(AnnotatedMethod method, String defaultName) { if (isGetter(method)) { return method.getName().substring(3); } if (isSetter(method)) { return method.getName().substring(3); } return defaultName; } private boolean isGetter(AnnotatedMethod method) { if (Modifier.isPublic(method.getModifiers()) && method.getGenericParameterTypes().length == 0) { if (method.getName().matches("^get[AZ].*") && !method.getGenericReturnType().equals(void.class)) return true; if (method.getName().matches("^is[AZ].*") && method.getGenericReturnType().equals(boolean.class)) return true; } return false; } private boolean isSetter(AnnotatedMethod method) { return Modifier.isPublic(method.getModifiers()) && method.getGenericReturnType().equals(void.class) && method.getGenericParameterTypes().length == 1 && method.getName().matches("^set[AZ].*"); } } 

Answer 1

I think this 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; } } 

Answer 2

I had the same problem.

This is my decision:

 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 depend on the correct method names.

Answer 3

You can set Jackson to be case sensitive:

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

Claims to fooobar.com/questions/56223 / ...

Answer 4

Although @JsonProperty does not work, I was able to use @JsonSetter and @JsonGetter to display the uppercase names of json fields.

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

Spring now serializes the object field as "ABC" rather than "abc".