Question 109338 in Json Question posted in
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Using json key as a field in java object

I have the following json that I want to serialize and deserialize.

{
  "name1": {
    "key1": "value1",
    "key2": "value2"
  }
}

Is it possible to use a key (eg. "name1" instead of "properites") as the name property in the java object either with annotation or with custom (de)serializer?

@lombok.Data
public class Example {

    private String name;

    private Map<String,String> properties = new HashMap<>();

    public Example(String name) {
        this.name = name;
    }

    public void add(String attr1, String val1) {
        properties.put(attr1, val1);
    }

    public static void main(String[] args) throws JsonProcessingException {
        Example bean = new Example("name1");
        bean.add("key1", "value1");
        bean.add("key2", "value2");

        String result = new ObjectMapper().writerWithDefaultPrettyPrinter().writeValueAsString(bean);
        System.out.println(result);
    }
}

The result without any config is the following:

{
  "name" : "name1",
  "properties" : {
    "key1" : "value1",
    "key2" : "value2"
  }
}
Tags:

2

Answers


  1. 0

    I’m not sure why you think you need the String name, this produces the JSON you want:

    public class Example {

    @JsonProperty("name1")
    private Map<String,String> properties = new HashMap<>();


    public void add(String attr1, String val1) {
        properties.put(attr1, val1);
    }

    public static void main(String[] args) throws JsonProcessingException {
        Example bean = new Example();
        bean.add("key1", "value1");
        bean.add("key2", "value2");

        String result = new ObjectMapper().writerWithDefaultPrettyPrinter().writeValueAsString(bean);
        System.out.println(result);
    }
}
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  2. 0

    If the JSON property "name1" is just an example and can vary (not known ahead of time), this might be what you’re looking for:

    @ToString
public class Example {

    @JsonIgnore
    private String name;

    @JsonIgnore
    private Map<String, Map<String,String>> properties;

    public Example() {
        properties = new HashMap<>();
    }

    public Example(String name) {
        this();
        this.name = name;
        properties.put(name, new HashMap<>());
    }

    public void add(String attr1, String val1) {
        properties.get(name).put(attr1, val1);
    }

    @JsonAnyGetter
    public Map<String, Map<String, String>> getProperties() {
        return properties;
    }

    @JsonAnySetter
    public void setProperties(String name, Map<String,String> props) {
        this.name = name;
        this.properties.put(name, props);
    }

    public static void main(String[] args) throws JsonProcessingException {
        Example bean = new Example("name1");
        bean.add("key1", "value1");
        bean.add("key2", "value2");

        ObjectMapper objectMapper = new ObjectMapper();
        String result = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(bean);
        System.out.println(result);

        Example parsed = objectMapper.readValue(result, Example.class);
        System.out.println(parsed);
    }
}

    The output of that is:

    {
  "name1" : {
    "key1" : "value1",
    "key2" : "value2"
  }
}

Example(name=name1, properties={name1={key1=value1, key2=value2}})

    The keys to this working are @JsonAnyGetter and @JsonAnySetter which are generally for serializing/deserializing arbitrary properties that don’t have dedicated, named fields or getters.

    By using @JsonIgnore on the fields themselves, this allows the "dynamic" properties to shine through instead of the internal representation of the Java object.

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