Question

我正在尝试创建一个可以跨类工作的@JsonDeserializer。我正在使用JAX-RS，并且传入的json字符串将包含snake case中的字段。我想覆盖json反序列化，以便我的java对象没有snake-case字段。由于java对象的创建发生在JAX-RS中，我在所有请求类上使用@JsonDeserializer注释。我当前的实现有一个通用基类，但我需要为所有具体类扩展它，以便我可以传入我想要创建的实际类。有没有办法更一般地做到这一点？

例如，我有多个请求对象，如下所示：

    @JsonDeserialize(using = MyRequestDeserializer.class)
    public class MyRequest {
    ....
    }

我创建了一个通用的反序列化器，如下所示：

public class GenericRequestDeserializer extends JsonDeserializer<Object> {

private static ObjectMapper objectMapper = new ObjectMapper();

@Override
public Object deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
    return null;
}

protected Object deserializeIt(JsonParser jsonParser, Class cls) {
    try {
        JsonNode node = jsonParser.getCodec().readTree(jsonParser);
        Iterator<String> fieldNames = node.fieldNames();

        Object object = cls.newInstance();

        while(fieldNames.hasNext()) {
            String fieldName = fieldNames.next();
            JsonNode value = node.get(fieldName);

            String newFieldName = convertFieldName(fieldName);

            //TODO: currently failing if I do not find a field, should the exception be swallowed?
            Class returnType = object.getClass().getMethod("get" + newFieldName).getReturnType();
            Method setMethod = object.getClass().getMethod("set" + newFieldName, returnType);

            Object valueToSet = null;
            if(value.isTextual()) {
                valueToSet = value.asText();
            } else if(value.isContainerNode()) {
                valueToSet = objectMapper.readValue(value.toString(), returnType);
            } else if (value.isInt()) {
                valueToSet = value.asInt();
            }

            setMethod.invoke(object, valueToSet);
        }

        return object;

    } catch (Exception e) {
        throw new TokenizationException(GatewayConstants.STATUS_SYSTEM_ERROR,
                "Error in deserializeIt for " + cls.getSimpleName() + " caused by " + e.getMessage(), e);
    }
}

private String convertFieldName(String fieldName) {

    StringBuilder newFieldName = new StringBuilder();

    int length = fieldName.length();
    boolean capitalize = true;  //first character should be capitalized

    for(int i = 0; i < length; i++) {
        char current = fieldName.charAt(i);

        if(current == '_') {
            //remove the underscore and capitalize the next character in line
            capitalize = true;
        } else if(capitalize) {
            newFieldName.append(Character.toUpperCase(current));
            capitalize = false;
        } else {
            newFieldName.append(current);
        }
    }

    return newFieldName.toString();
}

}

但是我仍然需要为每个请求创建一个新类，以便传入适当的类来创建：

public class MyRequestDeserializer extends GenericRequestDeserializer {
@Override
public Object deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
    return deserializeIt(jsonParser, MyRequest.class);
}
}

有没有办法摆脱所有MyRequestDeserializer类？换句话说，GenericRequestDeserializer可以找出实际反序列化的类吗？

Answer 1

所以我找到了一个更好的选择，可以将所有对象更改为蛇形。我没有在每个类上使用Serializers和Deserializers，而是在Spring中将一个ObjectMapper注入到JsonProvider中。 ObjectMapper已经支持一个属性，它将自动执行camel-case到snake-case。我只需要在我的类中覆盖扩展Application的getSingletons方法，如下所示：

public class MyApp extends Application {
....
@Override
public Set<Object> getSingletons() {
    final Set<Object> objects = new LinkedHashSet<Object>();


    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setPropertyNamingStrategy(
            PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

    objects.add(new JacksonJsonProvider(objectMapper));

    return objects;
}
}

Json反序列化器，适用于java中的不同类

1 个答案: