Adding a dynamic json property as java pojo for jackson

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滥情空心 2020-12-07 04:13

I need to create a Json payload like this from Java pojo :

{ \"update\" : {
    \"labels\" : [{\"add\" : \"A label\"} ]
    }
 }

so I crea

2条回答

猫巷女王i (楼主)

2020-12-07 04:55

You can use JsonAnyGetter annotation which allows to create dynamic key-value pairs. Below example shows how we can generate 3 different keys for the same Label class:

import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonRootName;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

public class JsonApp {

    public static void main(String[] args) throws Exception {
        AddLabel label = new AddLabel("A label");
        label.getLabels().add(AddLabel.Label.remove("Remove"));
        label.getLabels().add(AddLabel.Label.set("Set"));

        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        System.out.println(mapper.writeValueAsString(label));
    }
}

@JsonRootName(value = "update")
class AddLabel {

    @JsonProperty("labels")
    private List labels;

    public AddLabel(String labelName) {
        this.labels = new ArrayList<>();
        this.labels.add(Label.add(labelName));
    }

    public List getLabels() {
        return labels;
    }

    public static class Label {

        private final String key;
        private final String value;

        private Label(String key, String value) {
            this.key = key;
            this.value = value;
        }

        public static Label add(String value) {
            return new Label("add", value);
        }

        public static Label remove(String value) {
            return new Label("remove", value);
        }

        public static Label set(String value) {
            return new Label("set", value);
        }

        @JsonAnyGetter
        public Map getDynamic() {
            return Collections.singletonMap(key, value);
        }
    }
}

Above code prints:

{
  "labels" : [ {
    "add" : "A label"
  }, {
    "remove" : "Remove"
  }, {
    "set" : "Set"
  } ]
}