找不到Json對象（使用org.json）

Question

Microsoft Academic提供了一個API，用於從Microsoft學術中獲取一些常規信息。 響應類型是Json對象。 使用org.Json和以下代碼，我試圖讀取響應對象，但我失敗了（需要下載這些 jar + common-logging和common-codec）：

    URIBuilder builder = new URIBuilder("https://api.projectoxford.ai/academic/v1.0/evaluate?");

    builder.setParameter("expr", "Composite(AA.AuN=='jaime teevan')");
    builder.setParameter("count", "100");
    builder.setParameter("attributes", "Ti,CC");

     URI uri = builder.build();
     HttpGet request = new HttpGet(uri);

    request.setHeader("Ocp-Apim-Subscription-Key", "Your-Key");


        HttpClient httpclient = HttpClients.createDefault();

        HttpResponse response = httpclient.execute(request);
        HttpEntity entity = response.getEntity();


        if (entity != null) {

            JSONObject obj = new JSONObject(entity);


            JSONArray arr = obj.getJSONArray("entities");
            for (int i = 0; i < arr.length(); i++){

            String post_id = arr.getJSONObject(i).getString("Ti");
                System.out.println(post_id);

            }    

            System.out.println(EntityUtils.toString(entity));
        }

返回以下異常：

Exception in thread "main" org.json.JSONException: JSONObject["entities"] not found.
at org.json.JSONObject.get(JSONObject.java:471)
at org.json.JSONObject.getJSONArray(JSONObject.java:618)

如何解決這個問題？

編輯雖然很容易看到我在問題開頭提供的鏈接響應示例（Microsoft Academic），但為了方便讀者，我在這里展示：

    {
  "expr": "Composite(AA.AuN=='jaime teevan')",
  "entities": 
  [
    {
      "logprob": -15.08,
      "Ti": "personalizing search via automated analysis of interests and activities",

      "CC": 372,
    },
    {
      "logprob": -15.389,
      "Ti": "the perfect search engine is not enough a study of orienteering behavior in directed search",
      "CC": 237,


    }
  ]
}

Answer 1

對我來說似乎問題是你沒有將你的響應轉換為string ，你需要在將響應轉換為JSONObject之前將其轉換為string

    HttpEntity entity = response.getEntity();
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    try {
        entity.writeTo(os);
    } catch (IOException e1) {
    }
    String contentString = new String(os.toByteArray());

或者其他方式

InputStream instream = entity.getContent();
 BufferedReader reader = new BufferedReader(new InputStreamReader(instream));
    StringBuilder sb = new StringBuilder();

    String line = null;
    try {
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
String contentString  = sb.toString(); //  you can pass sb.toString() directly to jsonobject as well

現在將contentString傳遞給JSONObject

 JSONObject obj = new JSONObject(contentString);
 JSONArray arr = obj.getJSONArray("entities");

更新：您也可以使用@ÖmerFadılUsta建議的這個 ，但我強烈建議使用HttpURLConnection來提高安全性和性能

Answer 2

嘗試將字符串JsonData傳遞給JSONObject：

if (entity != null) {
    String jsonData = EntityUtils.toString(entity); 
    JSONObject obj = new JSONObject(jsonData);
    ........
    .....
}