De-serializing JSON to polymorphic object model using Spring and JsonTypeInfo annotation

Question

I have the following object model in my Spring MVC (v3.2.0.RELEASE) web application:

public class Order {   private Payment payment; }  @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = As.WRAPPER_OBJECT) @JsonSubTypes.Type(name = "creditCardPayment", value = CreditCardPayment.class) public interface Payment {}   @JsonTypeName("creditCardPayment") public class CreditCardPayment implements Payment {} 

When I serialise the Order class to JSON, I get the following result (which is exactly what I want):

{   "payment" : {     "creditCardPayment": {       ...     }  } 

Unfortunately, if I take the above JSON and try to de-serialise it back into my object model, I get the following exception:

Could not read JSON: Could not resolve type id 'creditCardPayment' into a subtype of [simple type, class Payment] at [Source: org.apache.catalina.connector.CoyoteInputStream@19629355; line: 1, column: 58] (through reference chain: Order["payment"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Could not resolve type id 'creditCardPayment' into a subtype of [simple type, class Payment] at [Source: org.apache.catalina.connector.CoyoteInputStream@19629355; line: 1, column: 58] (through reference chain: Order["payment"])

My application is configured via Spring JavaConf, as follows:

@Configuration @EnableWebMvc public class AppWebConf extends WebMvcConfigurerAdapter {      @Bean     public ObjectMapper objectMapper() {         ObjectMapper objectMapper = new ObjectMapper();         objectMapper.setSerializationInclusion(Include.NON_NULL);         objectMapper.configure(MapperFeature.DEFAULT_VIEW_INCLUSION, false);         return objectMapper;     }      @Bean     public MappingJackson2HttpMessageConverter mappingJacksonMessageConverter() {         MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();         converter.setObjectMapper(objectMapper());         return converter;     }      @Bean     public Jaxb2RootElementHttpMessageConverter jaxbMessageConverter() {         return new Jaxb2RootElementHttpMessageConverter();     }      @Override     public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {         converters.add(jaxbMessageConverter());         converters.add(mappingJacksonMessageConverter());     } } 

For testing, I have a controller with 2 methods, one returns an Order for HTTP GET request (this one works) and one that accepts an Order via a HTTP POST (this one fails), e.g.

@Controller public class TestController {      @ResponseBody     @RequestMapping(value = "/test", method = RequestMethod.GET)     public Order getTest() {}      @RequestMapping(value = "/test", method = RequestMethod.POST)     public void postTest(@RequestBody order) {}  } 

I have tried all suggestions from the various discussions on SO but so far had no luck. Can anyone spot what I'm doing wrong?

Answer 1

Try to register subtype using ObjectMapper.registerSubtypes instead of using annotations

Answer 2

The method registerSubtypes() works!

@JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=JsonTypeInfo.As.PROPERTY, property="type") public interface Geometry {   //... }  public class Point implements Geometry{   //... } public class Polygon implements Geometry{   //... } public class LineString implements Geometry{   //... }  GeoJson geojson= null; ObjectMapper mapper = new ObjectMapper(); mapper.disable(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES); mapper.registerSubtypes(Polygon.class,LineString.class,Point.class);  try {     geojson=mapper.readValue(source, GeoJson.class);             } catch (IOException e) {     e.printStackTrace(); } 

Note1: We use the Interface and the implementing classes. I fyou want jackson to de-serialize the classes as per their implementing classes, you have to register all of them using ObjectMapper's "registerSubtypes" method.

Note2: In addition you use, " @JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=JsonTypeInfo.As.PROPERTY, property="type")" as annotation with your Interface.

You can also define the order of properties when mapper writes a value of your POJO as a json.

This you can do using below annotation.

@JsonPropertyOrder({"type","crs","version","features"}) public class GeoJson {      private String type="FeatureCollection";     private List<Feature> features;     private String version="1.0.0";     private CRS crs = new CRS();     ........ } 

Hope this helps!