Jackson - How to process (deserialize) nested JSON?

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遇见更好的自我
遇见更好的自我 2020-11-29 01:18
{
  vendors: [
    {
      vendor: {
        id: 367,
        name: \"Kuhn-Pollich\",
        company_id: 1,
      }
    },
    {
      vendor: {
        id: 374,
           


        
3条回答
  •  慢半拍i
    慢半拍i (楼主)
    2020-11-29 02:00

    Here is a rough but more declarative solution. I haven't been able to get it down to a single annotation, but this seems to work well. Also not sure about performance on large data sets.

    Given this JSON:

    {
        "list": [
            {
                "wrapper": {
                    "name": "Jack"
                }
            },
            {
                "wrapper": {
                    "name": "Jane"
                }
            }
        ]
    }
    

    And these model objects:

    public class RootObject {
        @JsonProperty("list")
        @JsonDeserialize(contentUsing = SkipWrapperObjectDeserializer.class)
        @SkipWrapperObject("wrapper")
        public InnerObject[] innerObjects;
    }
    

    and

    public class InnerObject {
        @JsonProperty("name")
        public String name;
    }
    

    Where the Jackson voodoo is implemented like:

    @Retention(RetentionPolicy.RUNTIME)
    @JacksonAnnotation
    public @interface SkipWrapperObject {
        String value();
    }
    

    and

    public class SkipWrapperObjectDeserializer extends JsonDeserializer implements
            ContextualDeserializer {
        private Class wrappedType;
        private String wrapperKey;
    
        public JsonDeserializer createContextual(DeserializationContext ctxt,
                BeanProperty property) throws JsonMappingException {
            SkipWrapperObject skipWrapperObject = property
                    .getAnnotation(SkipWrapperObject.class);
            wrapperKey = skipWrapperObject.value();
            JavaType collectionType = property.getType();
            JavaType collectedType = collectionType.containedType(0);
            wrappedType = collectedType.getRawClass();
            return this;
        }
    
        @Override
        public Object deserialize(JsonParser parser, DeserializationContext ctxt)
                throws IOException, JsonProcessingException {
            ObjectMapper mapper = new ObjectMapper();
            ObjectNode objectNode = mapper.readTree(parser);
            JsonNode wrapped = objectNode.get(wrapperKey);
            Object mapped = mapIntoObject(wrapped);
            return mapped;
        }
    
        private Object mapIntoObject(JsonNode node) throws IOException,
                JsonProcessingException {
            JsonParser parser = node.traverse();
            ObjectMapper mapper = new ObjectMapper();
            return mapper.readValue(parser, wrappedType);
        }
    }
    
    
    

    Hope this is useful to someone!

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