RestTemplate map JSON key-value pair object with with dynamic keys

Question

I get a response of JSON key-value pair object with with dynamic keys for a HTTP request done using Java Spring RestTemplate as shown below.

Response:

{
    "1234x": {
        "id": "1234x",
        "description": "bla bla",
        ... 
    },
    "5678a": {
        "id": "5678a",
        "description": "bla bla bla",
        ... 
    },
    ...
}

How to map the response object to a POJO or a Map ?

I am using RestTemplate as following.

RestTemplate restTemplate = new RestTemplate();
String url = "my url";
HttpHeaders headers = new HttpHeaders();
HttpEntity entity = new HttpEntity(headers);
response = restTemplate.exchange(url, HttpMethod.GET, entity, ???);

Second approch is like : this link below https://stackoverflow.com/questions/35465273/jackson-de-serialize-json-with-dynamic-key — Himeshgiri gosvami, Nov 27 '18 at 06:52
Does json has same structure for all objects? How dynamic it is, parameter names or length changes? — Emre Savcı, Nov 27 '18 at 06:58
@Emre Savcı as you see keys are the ids. So its different everytime and number of key-value pairs also differ. — Shanika Ediriweera, Nov 27 '18 at 07:06

score 4 · Accepted Answer · answered Nov 27 '18 at 07:13

4

You can simply use ParameterizedTypeReference with Map (you can customize it according to your use case) :

response = restTemplate.exchange(url, HttpMethod.GET, entity, new ParameterizedTypeReference<Map<String, Object>>() {});

answered Nov 27 '18 at 07:13

Emre Savcı

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When I used this there is an error in unit test. `Mockito.when(restTemplate.exchange(......)).thenReturn(new ResponseEntity>(map, HttpStatus.ACCEPTED));`. It says `cannot resolve method thenReturn(...)` with the parameter type. – Shanika Ediriweera Nov 27 '18 at 07:55
Can you share full exception? It seems like it related with your return type passed to thenReturn method. – Emre Savcı Nov 27 '18 at 07:57
It is a syntax error `Cannot resolve method 'thenReturn(org.springframework.http.ResponseEntity>)'` – Shanika Ediriweera Nov 27 '18 at 08:07
You should give some value inside thenReturn() method like `thenReturn(ResponseEntity.ok(new HashMap()));` . – Emre Savcı Nov 27 '18 at 08:11
I gave a value. `thenReturn(new ResponseEntity>(map, HttpStatus.ACCEPTED));` – Shanika Ediriweera Nov 27 '18 at 08:47
Thanks. Got it fixed. Issue was with the Mockito matcher. Fixed referring https://stackoverflow.com/questions/29670463/match-generics-with-mockito – Shanika Ediriweera Nov 27 '18 at 09:59
I'm glad it helps – Emre Savcı Nov 27 '18 at 10:41

score 1 · Answer 2 · answered Nov 27 '18 at 06:59

You could use the new ObjectMapper.readValue() and specify TypeReference as new TypeReference<Map<String, SimplePOJO>>() {});

public static void main(String[] args) throws IOException {
    final String json = "{\"1234x\": {\"id\": \"1234x\", \"description\": \"bla bla\"}, \"5678a\": {\"id\": \"5678a\", \"description\": \"bla bla bla\"}}";
    Map<String, SimplePOJO> deserialize =
            new ObjectMapper().readValue(json, new TypeReference<Map<String, SimplePOJO>>() {});
}

public static class SimplePOJO {
    private String id;
    private String description;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        SimplePOJO that = (SimplePOJO) o;
        return Objects.equals(id, that.id) &&
                Objects.equals(description, that.description);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, description);
    }
}

@ShanikaEdiriweera `response = restTemplate.exchange(url, HttpMethod.GET, entity, String.class); Map deserialize = new ObjectMapper().readValue(response.getBody(), new TypeReference>() {});` — Mr. Skip, Nov 27 '18 at 07:13

RestTemplate map JSON key-value pair object with with dynamic keys

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