Jackson overcoming underscores in favor of camel-case

Question

I retrieve a JSON string from internet  like most JSON I ve seen it includes long keys that are separated by underscores  Essentially  my goal is to deserialize JSON into java-objects  but I don t use underscores in java-code   For instance  I might have a User class with firstName field in camel-case  simultaneously I  need somehow to  tell Jackson to map first name key from JSON to firstName class field  Is it possible   class User      protected String firstName      protected String getFirstName   return firstName

User · Answer

If its a spring boot application  In application properties file  just use      spring jackson property-naming-strategy SNAKE CASE   Or Annotate the model class with this annotation       JsonNaming PropertyNamingStrategy SnakeCaseStrategy class

User · Answer

You can configure the ObjectMapper to convert camel case to names with an underscore   objectMapper setPropertyNamingStrategy PropertyNamingStrategy SNAKE CASE     Or annotate a specific model class with this annotation    JsonNaming PropertyNamingStrategy SnakeCaseStrategy class    Before Jackson 2 7  the constant was named   PropertyNamingStrategy CAMEL CASE TO LOWER CASE WITH UNDERSCORES

User · Answer

The above answers regarding  JsonProperty and CAMEL CASE TO LOWER CASE WITH UNDERSCORES are 100  accurate  although some people  like me  might be trying to do this inside a Spring MVC application with code-based configuration  Here s sample code  that I have inside Beans java  to achieve the desired effect    Bean public ObjectMapper jacksonObjectMapper         return new ObjectMapper   setPropertyNamingStrategy              PropertyNamingStrategy CAMEL CASE TO LOWER CASE WITH UNDERSCORES

User · Answer

You should use the  JsonProperty on the field you want to change the default name mapping   class User       JsonProperty  first name       protected String firstName      protected String getFirstName   return firstName       For more info  the API

User · Answer

There are few answers here indicating both strategies for 2 different versions of Jackson library below   For Jackson 2 6    ObjectMapper objMapper   new ObjectMapper new JsonFactory        or YAMLFactory   objMapper setNamingStrategy       PropertyNamingStrategy CAMEL CASE TO LOWER CASE WITH UNDERSCORES     For Jackson 2 7    ObjectMapper objMapper   new ObjectMapper new JsonFactory        or YAMLFactory   objMapper setNamingStrategy       PropertyNamingStrategy SNAKE CASE

User · Answer

If you want this for a Single Class  you can use the PropertyNamingStrategy with the  JsonNaming  something like this    JsonNaming PropertyNamingStrategy LowerCaseWithUnderscoresStrategy class  public static class Request        String businessName      String businessLegalName       Will serialize to          business name             business legal name           Since Jackson 2 7 the LowerCaseWithUnderscoresStrategy in deprecated in favor of SnakeCaseStrategy  so you should use    JsonNaming PropertyNamingStrategy SnakeCaseStrategy class  public static class Request        String businessName      String businessLegalName

User · Answer

The current best practice is to configure Jackson within the application yml  or properties  file   Example   spring    jackson      property-naming-strategy  SNAKE CASE   If you have more complex configuration requirements  you can also configure Jackson programmatically    import com fasterxml jackson databind PropertyNamingStrategy  import org springframework context annotation Bean  import org springframework context annotation Configuration  import org springframework http converter json Jackson2ObjectMapperBuilder    Configuration public class JacksonConfiguration         Bean     public Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder             return new Jackson2ObjectMapperBuilder                    propertyNamingStrategy PropertyNamingStrategy SNAKE CASE              insert other configurations

User · Answer

Annotating all model classes looks to me as an overkill and Kenny s answer didn t work for me https   stackoverflow com a 43271115 4437153  The result of serialization was still camel case  I realised that there is a problem with my spring configuration  so I had to tackle that problem from another side  Hopefully someone finds it useful  but if I m doing something against springs  rules then please let me know  Solution for Spring MVC 5 2 5 and Jackson 2 11 2  Configuration  EnableWebMvc public class WebConfig implements WebMvcConfigurer        Override     public void configureMessageConverters List lt HttpMessageConverter lt   gt  gt  converters            ObjectMapper objectMapper   new ObjectMapper            objectMapper setPropertyNamingStrategy PropertyNamingStrategy SNAKE CASE                       MappingJackson2HttpMessageConverter converter   new MappingJackson2HttpMessageConverter            converter setObjectMapper objectMapper           converters add converter

[java] Jackson overcoming underscores in favor of camel-case

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