无法使用 Java 的 HttpURLConnection 从 Flickr API 获取结果

Question

我在查询 Flickr REST API 以搜索照片时遇到问题：

https://www.flickr.com/services/api/explore/flickr.photos.search

我正在 Android 中使用 HttpURLConnection 编写一个小测试 app，我 不想使用任何frameworks（例如OkHttp等）因为这只是简单的学习练习。

我遇到的问题是，虽然 我的 HttpURL 连接 returns 200，但没有 JSON 响应 。但是当我从我的日志中获取构建的 REST URL 时，例如：

https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=API_KEY&tags=basketball&format=json&nojsoncallback=1&api_sig=API_SIG

然后复制粘贴到浏览器，我可以看到正确的JSON。

这是浏览器 returns:
JSON 的片段
{"photos":{"page":1,"pages":2614,"perpage":100,"total":"261380","photo":[{"id":"39168832065","owner":"23023080@N02","secret":"1fb9ee772a","server":"4615","farm":5,"title":"_MG_2714_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194325488","owner":"23023080@N02","secret":"3bc00e37ee","server":"4656","farm":5,"title":"_MG_2719_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"39168829925","owner":"23023080@N02","secret":"15580858ce","server":"4695","farm":5,"title":"_MG_2723_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194323798","owner":"23023080@N02","secret":"c5e445bd6e","server":"4743","farm":5,"title":"_MG_2727_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"39168828415","owner":"23023080@N02","secret":"89b54b28bc","server":"4648","farm":5,"title":"_MG_2729_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194322658","owner":"23023080@N02","secret":"7eff365389","server":"4648","farm":5,"title":"_MG_2732_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"39168826725","owner":"23023080@N02","secret":"2eda660b60","server":"4723","farm":5,"title":"_MG_2734_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194321108","owner":"23023080@N02","secret":"0c794e38a8","server":"4765","farm":5,"title":"_MG_2735_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40034887842","owner":"23023080@N02","secret":"6269997f0f","server":"4755","farm":5,"title":"_MG_2737_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194319778","owner":"23023080@N02","secret":"32991c9151","server":"4763","farm":5,"title":"_MG_2739_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194319168","owner":"23023080@N02","secret":"4dd5555f5c","server":"4709","farm":5,"title":"_MG_2746_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40034885802","owner":"23023080@N02","secret":"3f9c5031db","server":"4671","farm":5,"title":"_MG_2747_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"26194317818","owner":"23023080@N02","secret":"e20b503f8f","server":"4668","farm":5,"title":"_MG_2757_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40067785161","owner":"23023080@N02","secret":"4ab87667fd","server":"4612","farm":5,"title":"_MG_2760_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40034884132","owner":"23023080@N02","secret":"235b7dc32d","server":"4744","farm":5,"title":"_MG_2762_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40067784231","owner":"23023080@N02","secret":"0bbae58322","server":"4622","farm":5,"title":"_MG_2763_edit","ispublic":1,"isfriend":0,"isfamily":0},{"id":"40034882942","owner":"23023080@N02","secret":"30345b6b7b","server":"4626","farm":5,"title":"_MG_2764_edit","ispublic":1,"isfriend":0,"isfamily":0},

为什么代码不是 getting/reading 来自连接输入流的 JSON？

package com.bing.ary.xyz; import android.os.AsyncTask; import android.util.Log; import com.google.gson.JsonElement; import com.google.gson.JsonObject; import com.google.gson.JsonParser; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import javax.net.ssl.HttpsURLConnection; import java.net.URL; public class SearchFlickerAsync extends AsyncTask<String, Void, flikrPhotosResponse> { private static final String TAG = "SearchFlickerAsync"; private String query; public SearchFlickerAsync(String query) { this.query = query; } public String getQuery() { return query; } public void setQuery(String query) { this.query = query; } @Override protected void onPreExecute() { super.onPreExecute(); } @Override protected flikrPhotosResponse doInBackground(String... query) { Log.i(TAG,"doInBackground(), SearchFlickerAsync input param:"+query); HttpsURLConnection httpURLConnection = null; flikrPhotosResponse FlikrPhotosResponse = null; JsonElement jsonElemnt = null; JsonObject jsonObject = null; String queryUrl = null; StringBuilder queryBuilder = null; try { //create url string queryBuilder = new StringBuilder(); queryBuilder.append(flickerApi.baseUrl); queryBuilder.append(flickerApi.searchFlicker); queryBuilder.append(flickerApi.flickrQuery_key + flickerApi.Key); queryBuilder.append(flickerApi.flickrQuery_tag); queryBuilder.append(this.query); queryBuilder.append("&format=json"); queryBuilder.append("&nojsoncallback=1&api_sig=be97f5275f5a128fbe69dc2cde2560b9"); //instantiate url for connection URL url = new URL(queryBuilder.toString()); httpURLConnection = (HttpsURLConnection) url.openConnection(); httpURLConnection.setRequestMethod("GET"); httpURLConnection.setUseCaches(false); httpURLConnection.setAllowUserInteraction(false); httpURLConnection.setRequestProperty("Content-length", "0"); httpURLConnection.connect(); //no authorization token needed public API httpURLConnection.setRequestProperty("Authorization", ""); Log.i(TAG,"doInBackground(), http request:"+url.toString()); int status = httpURLConnection.getResponseCode(); switch (status) { case 200: case 201: Log.i(TAG,"doInBackground(), http response status:"+status); BufferedReader br = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream())); StringBuilder sb = new StringBuilder(); String line; while ((line = br.readLine()) != null) { sb.append(line + "\n"); } Log.i(TAG,"doInBackground(), http response line:"+line); jsonElemnt = new JsonParser().parse(sb.toString()); jsonObject = jsonElemnt.getAsJsonObject(); /*Further parse & instantiate FlikrPhotosResponse = */ br.close(); break; //TODO: ERRORS https://www.flickr.com/services/api/flickr.groups.search.html default: Log.e(TAG,"doInBackground(), http response error status:"+status); //TODO: handle error responses break; } } catch (IOException ex) { ex.printStackTrace(); } catch (Exception ex) { ex.printStackTrace(); } finally { if (httpURLConnection != null) { try { httpURLConnection.disconnect(); } catch (Exception ex) { ex.printStackTrace(); } } } return FlikrPhotosResponse; }//end doInBackgroud protected void onPostExecute(flikrPhotosResponse FlikrPhotosResponse) { Log.i(TAG,"onPostExecute(), FlikrPhotosResponse:"+FlikrPhotosResponse); } }//end class

相关日志无errpr或异常：

02-04 13:24:12.037 3750-4270/com.bing.ary.skywelltest I/SearchFlickerAsync: doInBackground(), http request:https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=37ae86d629a2e4a62917253419cb9e94&tags=basketball&format=json&nojsoncallback=1&api_sig=be97f5275f5a128fbe69dc2cde2560b9 02-04 13:24:12.220 3750-4270/com.bing.ary.skywelltest I/SearchFlickerAsync: doInBackground(), http response status:200 02-04 13:24:12.221 3750-4270/com.bing.ary.skywelltest I/SearchFlickerAsync: doInBackground(), http response line:null

我也

Answer 1

你记录的是错误的东西：

while ((line = br.readLine()) != null) {
    sb.append(line + "\n");
}
Log.i(TAG,"doInBackground(), http response line:"+line);

当然line此时为null。这就是循环终止的原因。您应该记录 sb.toString().

注意：

您不需要以下任何一项：

httpURLConnection.setRequestMethod("GET");
httpURLConnection.setRequestProperty("Content-length", "0");
httpURLConnection.connect();

您需要使用 HttpsURLConnection 的评论中的许多说法都是不正确的。使用 HttpURLConnection 是完全有效的，即使 URL 是一个 HTTPS，只要你不需要 HttpsURLConnection 的额外方法，因为 HttpsURLConnection 扩展 [=15] =].

无法使用 Java 的 HttpURLConnection 从 Flickr API 获取结果

Not getting result back from Flickr API using Java's HttpURLConnection

java

rest

android

flickr

httpurlconnection