CODEWITHSUNDEEP
javajsonspringspring-mvcspring-boot
JONKI
JONKI

Reputation: 595

The elements of collections of a deserialized JSON object are LinkedHashMap

I am sending a request to the controller https://pastebin.com/d4SHZuZh. JSON deserialize using Builder from this class. @JsonDeserialize(builder = ContributionNewRequest.Builder.class)

The elements of the collection are ? extends MovieInfoDTO objects inheriting from MovieInfoDTO.

when getting items from e.g. list elementsToAdd

contribution.getElementsToAdd()
            .forEach(boxOffice -> {
                ...
            });

it turns out that the boxOffice element is a java.util.LinkedHashMap object.

I found a mention on the internet on the Internet http://www.baeldung.com/jackson-collection-array that JSON default sets the elements of the collection as LinkedHashMap.

What do I need to do to make the objects of the correct type?

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.jonki.popcorn.common.dto.movie.BoxOffice
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_171]

Upvotes: 2

Views: 1561

Answers (2)

Anh N. Nguyen
Anh N. Nguyen

Reputation: 509

You should custom your deserialize builder.

Try something like this

public class CustomDeserializer extends StdDeserializer<List<? extends MovieInfoDTO>> {
    protected CustomDeserializer(Class<?> vc) {
        super(vc);
    }

    @Override
    public List<? extends MovieInfoDTO> deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        String json = jsonParser.getText();
        TypeReference type = new TypeReference<List<? extends MovieInfoDTO>>() {};
        return objectMapper.readValue(json, type);
    }
}

Finally add @JsonDeserialize(using = CustomDeserializer.class) before your elementsToAdd property

Hope this will help you a bit.

Upvotes: 3

Alien
Alien

Reputation: 15878

Try to convert it using following code. 

public <T> List<T> jsonToObjectList(String json, Class<T> tClass) throws IOException {
            ObjectMapper objectMapper = new ObjectMapper();
            List<T> ts = objectMapper.readValue(json, objectMapper.getTypeFactory().constructCollectionType(ArrayList.class, tClass));
            return ts;
        }

Upvotes: 0

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