Jackson：如何忽略字段的数据类型不匹配

Question

我在 Spring Rest 模板中收到 json 响应，并尝试将其投射到自定义对象上。

@JsonIgnoreProperties(ignoreUnknown = true)
public class DataItems {

private String deviceId;
    private String dataSourceName;
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss.ms+0000")
    private Date timestamp;
    private String mName;
    private String mVersion;
    private double value;


    /**
     * constructors and getters and setters
     */

现在，有时，我得到的这个双精度值是字符串垃圾值。

那么，如何在投射时忽略这些记录。下面是我的铸造代码。

ObjectMapper mapper = new ObjectMapper();
DataItems dataItems =  mapper.readValue(/*String*/json),DataItems.class);

示例 Json：

[{
        "value": 26.394289,
        "deviceId": "97572545-3768-6070-0B09-1A566D8F6BC1",
        "dataSourceName": "AQM",
        "timestamp": "2016-11-04T05:24:55.000+0000",
        "mName": "SENS_TEMPERATURE",
        "mVersion": "1.0"
      },
      {
        "value": 26.396435,
        "deviceId": "97572545-3768-6070-0B09-1A566D8F6BC1",
        "dataSourceName": "AQM",
        "timestamp": "2016-11-04T05:25:58.000+0000",
        "mName": "SENS_TEMPERATURE",
        "mVersion": "1.0"
      },
      {
        "value": "{\"timestamp\": 1478220851, \"metric\": \"SENS_TAMPER\", \"value\": \"1\", \"source\": \"AQM\"}",
        "deviceId": "97572545-3768-6070-0B09-1A566D8F6BC1",
        "dataSourceName": "AQM",
        "timestamp": "2016-11-04T00:54:11.000+0000",
        "mName": "SENS_UNREGISTERED",
        "mVersion": "1.0"
      }]

Answer 1

自定义解串器可以解决此问题。如果无法反序列化 double 值，自定义反序列化器将设置默认值"0.0"。

更改 POJO：-

@JsonDeserialize(using = DoubleDeserializer.class)
private Double value;

DoubleDeserializer - 自定义解串器：-

public class DoubleDeserializer extends JsonDeserializer<Double> {

    @Override
    public Double deserialize(JsonParser jsonParser, DeserializationContext deserializationContext)
            throws IOException, JsonProcessingException {

        String doubleValue = jsonParser.readValueAs(String.class);

        try {
            return Double.valueOf(doubleValue);
        } catch (NumberFormatException ne) {
            System.out.println("Default value is set as the value in json is not compatible with double value");
            return new Double(0);           
        }

    }
}