How to Deserialize Nested Lists Using Jackson in Java?

How can I deserialize nested lists using Jackson in Java?

@JsonProperty("items")
private List<List<Item>> items;

Deserializing nested lists with Jackson in Java can be complex due to the intricacies of handling generic collections. This guide provides a comprehensive approach to efficiently achieve this using Jackson's ObjectMapper.

ObjectMapper objectMapper = new ObjectMapper();
List<List<Item>> items = objectMapper.readValue(
    jsonString,
    new TypeReference<List<List<Item>>>() {});

Causes

• Not using the correct generic type while defining the data structure.
• Omitting necessary annotations for serialization/deserialization.

Solutions

• Ensure your Java class structure accurately represents the JSON format you want to deserialize.
• Use the `@JsonProperty` annotation to specify the mapping between your JSON keys and Java fields.
• Utilize `ObjectMapper.readValue()` method with the correct type reference when deserializing nested lists.

Mistake: Ignoring type information during deserialization.

Solution: Always use `TypeReference` to maintain type safety when deserializing collections.

Mistake: Forgetting to include getter/setter methods or annotations in the data class.

Solution: Ensure the data class has proper getters/setters or use public fields.