在一个字段中反序列化多个类型的JSON

Question

我想反序列化JSON(使用Jackson 1.9.11和RestTemplate 1.0.1),其中一个字段可能具有更多类型含义,例如:

    {"responseId":123,"response":"error"}

要么

    {"responseId":123,"response":{"foo":"bar", ... }}

一个或其他案例可以使用一个特定类型的setter(String od自定义Response类)正常工作,但是当我放入我的实体bean覆盖setter以便能够处理这两种情况时,抛出异常:

Caused by: org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [xxxx.templates.ExportResponse] and content type [application/json;charset=utf-8]

我正在考虑三个解决方案,但我没有得到任何解决方案:

• 仅使用String setter并在内部使用ObjectMapper来解组该字符串,如果它不等于"error",但是当JS Array出现时,它不是字符串所以不使用String setter :(.
• 使用多态类型处理(@JsonTypeInfo注释)与自己的JsonDeserializer扩展 - 我仍然试图理解这一点并实现.
• 创建HttpMessageConverter列表并放入所有消息转换器,我可以使用.但我认为这一步是不必要的,因为只使用MappingJacksonHttpMessageConverter,我是对的吗？

编辑:现在如何运作

实体bean中的setter:

@JsonDeserialize(using = ResponseDeserializer.class)
public void setResponse(Object responseObject) {
    if(responseObject instanceof Response)
        response = (Response) responseObject;
}

在ResponseDeserializer中反序列化方法:

public Response deserialize(JsonParser parser, DeserializationContext context) throws IOException, JsonProcessingException {
    Response response = new Response();

    if(JsonToken.START_OBJECT.equals(parser.getCurrentToken())) {
        ObjectMapper mapper = new ObjectMapper();
        response = mapper.readValue(parser, Response.class);
    } else
        throw new JsonMappingException("Unexpected token received.");

    return response;
}

Answer 1

实现这一目标的唯一方法是使用自定义反序列化器.

这是一个例子:

ObjectMapper mapper = new ObjectMapper();
SimpleModule testModule = new SimpleModule("MyModule", new Version(1, 0, 0, null));
testModule.addDeserializer(Response.class, new ResponseJsonDeserializer());
mapper.registerModule(testModule);

以下是如何编写(至少我将如何编写)反序列化器:

class ResponseJsonDeserializer extends JsonDeserializer<Response>  {
  @Override
  public Responsedeserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
    Response response = new Response();
    if(jp.getCurrentToken() == JsonToken.VALUE_STRING) {
        response.setError(jp.getText());
    } else {
       // Deserialize object
    }
    return response;
  }
}

class Response {
   private String error;
   private Object otherObject; // Use the real type of your object

   public boolean isError() {
      return error != null;
   }

   // Getters and setters

}