JSON 使用 spring 中的 jackson 解析？

Question

I have the following JSON

{
  "ads": [
    {
  "228029_228029": {
    "ad_id": "228029",
    "duration": 10,
    "m3u8_text": {
      "_1280p": "#EXTM3U\n#EXT-X-VERSION:3\n#EXT-X-ALLOW-CACHE:YES\n#EXT-X-TARGETDURATION:7\n#EXT-X-MEDIA-SEQUENCE:0\n#EXTINF:7.120000,\n_1280p_0000.ts\n#EXTINF:2.880000,\n_1280p_0001.ts\n#EXT-X-ENDLIST\n",
      "_320p": "#EXTM3U\n#EXT-X-VERSION:3\n#EXT-X-ALLOW-CACHE:YES\n#EXT-X-TARGETDURATION:7\n#EXT-X-MEDIA-SEQUENCE:0\n#EXTINF:7.120000,\n_320p_0000.ts\n#EXTINF:2.880000,\n_320p_0001.ts\n#EXT-X-ENDLIST\n"
    }
  }
},
{
  "228845_228845": {
    "ad_id": "228845",
    "duration": 24,
    "m3u8_text": {
      "_1280p": "#EXTM3U\n#EXT-X-VERSION:3\n#EXT-X-ALLOW-CACHE:YES\n#EXT-X-TARGETDURATION:8\n#EXT-X-MEDIA-SEQUENCE:0\n#EXTINF:7.840000,\n_1280p_0000.ts\n#EXTINF:6.880000,\n_1280p_0001.ts\n#EXTINF:6.680000,\n_1280p_0002.ts\n#EXTINF:2.600000,\n_1280p_0003.ts\n#EXT-X-ENDLIST\n",
      "_320p": "#EXTM3U\n#EXT-X-VERSION:3\n#EXT-X-ALLOW-CACHE:YES\n#EXT-X-TARGETDURATION:8\n#EXT-X-MEDIA-SEQUENCE:0\n#EXTINF:7.840000,\n_320p_0000.ts\n#EXTINF:6.880000,\n_320p_0001.ts\n#EXTINF:6.680000,\n_320p_0002.ts\n#EXTINF:2.600000,\n_320p_0003.ts\n#EXT-X-ENDLIST\n"
    }
  }
}
  ],
  "total_duration": 80
}

I have created the respective model class as This is the root model

@JsonIgnoreProperties(ignoreUnknown = true)
public class AdsResponse {
@JsonProperty("ads")
List<Ad> ads;
@JsonProperty("total_duration")
long totalDuration;
}

Then the ads model

public class Ad {
Map<String,AdInfo> ad;}

Then the AdInfo model

public class AdInfo {
@JsonProperty("m3u8_text")
AdManifest adManifest;
int duration;
@JsonProperty("ad_id")
String adId;}

Then the manifest model

public class AdManifest {
@JsonProperty("_1280p")
String _1280p;
@JsonProperty("_320p")
String _320p;}

When I try to parse this using below code

AdsResponse response = new ObjectMapper().readValue(
                res,
                AdsResponse.class);

I get the empy ad object

AdsResponse{ads=[Ad{ad=null}, Ad{ad=null}, totalDuration=80}

What is wrong here?

Answer 1

You don't actually need the Ad class, it's just a Map<> . AdResponse can look like this:

public class AdsResponse {

    @JsonProperty("ads")
    List<Map<String, AdInfo>> ads;

    @JsonProperty("total_duration")
    long totalDuration;

If the keys in the map were predictable, you could make them properties on the Ad class and then Jackson would map them properly. But since they're not (they look like some kind of ID), mapping them to a Map<> is probably the best option.

As an alternative, if you want or need to have the Ad objects, you can map them like this:

public class Ad {

    Map<String, AdInfo> adInfo = new HashMap<>();

    @JsonAnySetter
    public void setAds(String key, AdInfo value) {
        adInfo.put(key, value);
    }
}

With that, and AdResponse defined the way you have it in the question , you'll get populated Ad instances, each of which has a Map<> with only 1 key/value pair. For an even simpler (and probably more sensible model, you can eliminate the Map if there is only ever 1 key in an Ad , like this:

public class Ad {

    private AdInfo adInfo;

    @JsonAnySetter
    public void setAdInfo(String ignored, AdInfo value) {
        this.adInfo = value;
    }
}