java - 无法写入 JSON : Direct self-reference leading to cycle

Question

收到此错误:

nested exception is com.fasterxml.jackson.databind.JsonMappingException: Direct self-reference leading to cycle (through reference chain: com.google.gson.JsonObject["asJsonObject"])

当尝试这样做时:

 restTemplate.postForObject(url_final, convertedObject, Object[].class);

其中 convertedObject 是 JSONObject，urlfinal 是 String url。

有效负载是:

"data" : [
  {"FILENAME":"EEC1.TXT",
   "ERRORDESCRIPTION":"FTD-07-INVALID CHARACTER FOUND IN THE FILE.",
   "LINENO":3},
  {"FILENAME":"SEC1.TXT",
   "ERRORDESCRIPTION":"26-FTD-07-INVALID CHARACTER FOUND IN THE FILE.",
    "LINENO":447}]

我的代码:

JSONObject output = new JSONObject(payload);
JSONArray jsonArray = output.getJSONArray("data");
JSONObject objects = jsonArray.getJSONObject(0);
String fileName = objects.getString("FILENAME");
int lineNumber = objects.getInt("LINENO");
String errordesc = objects.getString("ERRORDESCRIPTION");
String tempor = "{\"activityType\": \"trial.start\",\"aFileName\":\""  
              + fileName
              + "\",\"aLINENO\": \""
              + lineNumber
              + "\",\"aREFNO\": \"" 
              + TxnNo
              + "\",    \"aERRORDESCRIPTION\": \""+errordesc+"\"}";
JsonObject convertedObject = new Gson().fromJson(tempor, JsonObject.class);
restTemplate.postForObject(url_final, convertedObject, Object[].class);

Answer 1

在十行中，您混合了 3 个不同的 JSON 库:

• JSONObject 来自org.json .
• Gson 来自 Google 的 gson .
• restTemplate 在幕后使用 Jackson .

您应该跳过前两个并仅使用Jackson。更改后的上述代码可能如下所示:

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.json.JsonMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;

....

ObjectMapper mapper = JsonMapper.builder().build();

JsonNode output = mapper.readTree(payload);

ArrayNode jsonArray = (ArrayNode)output.get("data");
JsonNode objects = jsonArray.get(0);
String fileName = objects.get("FILENAME").asText();
int lineNumber = objects.get("LINENO").asInt();
String errordesc = objects.get("ERRORDESCRIPTION").asText();
String tempor = "{\"activityType\": \"trial.start\",\"aFileName\":\""
        + fileName
        + "\",\"aLINENO\": \""
        + lineNumber
        + "\",\"aREFNO\": \""
        + TxnNo
        + "\",    \"aERRORDESCRIPTION\": \""+errordesc+"\"}";
JsonNode convertedObject = mapper.readTree(tempor);

自版本 2.10.0您可以使用 JsonMapper.builder().build() 但在以前的版本中，您可以通过 new ObjectMapper() 创建新实例，这也很好。