Question

我一直在尝试反序列化从this API收到的数据：

{
  "result": "success",
  "timestamp": 1521038012878,
  "data": {
    "GB": 14,
    "DE": 2,
    "US": 2
  },
  "totalIsPublic": true,
  "advanced": false,
  "totalDownloads": {
    "GB": 14,
    "DE": 2,
    "US": 2
  }
}

这是POJO课程：

public class BintrayDownloadCounts {

    private List<Integer> totalDownloads = new ArrayList<>();

    @JsonProperty("totalDownloads")
    public List<Integer> getTotalDownloads() {
        return totalDownloads;
    }

    public void setTotalDownloads(List<Integer> totalDownloads) {
        this.totalDownloads = totalDownloads;
    }
}

当我尝试使用：

进行反序列化时

downloadCounts = mapper.readValue(json, BintrayDownloadCounts.class);

我收到此错误：

 com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.Integer out of START_OBJECT token

我看到很多问题包含此错误，但我无法找到针对此特定用例的解决方案。可以注意到totalDownloads对象是动态的，即其内容不是恒定的。

Answer 1

totalDownloads属性不是数组，因此无法映射到List<Integer>。请改用Map<String, Integer>并确保告诉Jackson忽略未映射的属性以避免映射错误：

@JsonIgnoreProperties(ignoreUnknown = true)
public class BintrayDownloadCounts {

    @JsonProperty("totalDownloads")
    private Map<String, Integer> totalDownloads;

    public Map<String, Integer> getTotalDownloads() {
        return totalDownloads;
    }

    public void setTotalDownloads(Map<String, Integer> totalDownloads) {
        this.totalDownloads = totalDownloads;
    }
}

然后你很高兴：

ObjectMapper mapper = new ObjectMapper();
BintrayDownloadCounts downloadCounts = mapper.readValue(json, BintrayDownloadCounts.class);

使用Jackson反序列化这个Json对象？

1 个答案: