ncphillips ncphillips - 7 months ago 184
Java Question

How to serialize and deserialize Java Enums as JSON objects with Jackson

Given an Enum:

public enum CarStatus {
NEW("Right off the lot"),
USED("Has had several owners"),
ANTIQUE("Over 25 years old");

public String description;

public CarStatus(String description) {
this.description = description;
}
}


How can we set it up so Jackson can serialize and deserialize an instance of this Enum into and from the following format.

{
"name": "NEW",
"description": "Right off the lot"
}


The default is to simply serialize enums into Strings. For example
"NEW"
.

Answer
  1. Use the JsonFormat annotation to get Jackson to deserailze the enum as a JSON object.
  2. Create a static constructor accepting a JsonNode and annotate said constructor with @JsonCreator.
  3. Create a getter for the enum's name.

Here's an example.

// 1
@JsonFormat(shape = JsonFormat.Shape.Object)
public enum CarStatus {
    NEW("Right off the lot"),
    USED("Has had several owners"),
    ANTIQUE("Over 25 years old");

    public String description;

    public CarStatus(String description) {
        this.description = description;
    }

    // 2
    @JsonCreator
    public static CarStatus fromNode(JsonNode node) {
        if (!node.has("name"))
            return null;

        String name = node.get("name").asText();

        return CarStatus.valueOf(name);
    }

    // 3
    @JsonProperty
    public String getName() {
        return name();
    }
}
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