java - 如何使用 Jackson 的本地化小数点分隔符反序列化浮点值

Question

我正在用 Jackson 解析的输入流包含纬度和经度值，例如此处:

{
    "name": "product 23",
    "latitude": "52,48264",
    "longitude": "13,31822"
}

出于某种原因，服务器使用逗号 作为产生InvalidFormatException 的小数点分隔符。由于我无法更改服务器输出格式，因此我想教 Jackson 的 ObjectMapper 来处理这些情况。相关代码如下:

public static Object getProducts(final String inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        return objectMapper.readValue(inputStream,
                new TypeReference<Product>() {}
        );
    } catch (UnrecognizedPropertyException e) {
        e.printStackTrace();
    } catch (InvalidFormatException e) {
        e.printStackTrace();
    } catch (JsonMappingException e) {
        e.printStackTrace();
    } catch (JsonParseException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

这是 POJO:

import com.fasterxml.jackson.annotation.JsonProperty;

public class Product {

    @JsonProperty("name")
    public String name;
    @JsonProperty("latitude")
    public float latitude;
    @JsonProperty("longitude")
    public float longitude;

}

我如何告诉 Jackson 这些坐标值带有德语语言环境？

---

我想 a custom deserializer for the specific fields as discussed here将是要走的路。我起草了这个:

public class GermanFloatDeserializer extends JsonDeserializer<Float> {

    @Override
    public Float deserialize(JsonParser parser, DeserializationContext context)
            throws IOException {
        // TODO Do some comma magic
        return floatValue;
    }

}

那么 POJO 看起来像这样:

import com.fasterxml.jackson.annotation.JsonProperty;

public class Product {

    @JsonProperty("name")
    public String name;
    @JsonDeserialize(using = GermanFloatDeserializer.class, as = Float.class)
    @JsonProperty("latitude")
    public float latitude;
    @JsonDeserialize(using = GermanFloatDeserializer.class, as = Float.class)
    @JsonProperty("longitude")
    public float longitude;

}

Answer 1

我想出了以下解决方案:

public class FlexibleFloatDeserializer extends JsonDeserializer<Float> {

    @Override
    public Float deserialize(JsonParser parser, DeserializationContext context)
            throws IOException {
        String floatString = parser.getText();
        if (floatString.contains(",")) {
            floatString = floatString.replace(",", ".");
        }
        return Float.valueOf(floatString);
    }

}

...

public class Product {

    @JsonProperty("name")
    public String name;
    @JsonDeserialize(using = FlexibleFloatDeserializer.class)
    @JsonProperty("latitude")
    public float latitude;
    @JsonDeserialize(using = FlexibleFloatDeserializer.class)
    @JsonProperty("longitude")
    public float longitude;

}

我仍然想知道为什么当我将返回值类指定为 as = Float.class 时它不起作用，如 documentation of JsonDeserialize 中所示.它读起来好像我应该使用一个或另一个而不是两者。不管怎样，文档还声称 as = 将在定义 using = 时被忽略:

if using() is also used it has precedence (since it directly specified deserializer, whereas this would only be used to locate the deserializer) and value of this annotation property is ignored.