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
我正在使用HttpURLConnection在Android中编写一个小型测试应用程序，并且我不想使用任何框架（例如OkHttp等），因为这只是简单的学习练习。
我遇到的问题是，尽管我的HttpURLConnection返回200，但是没有JSON响应。但是，当我从日志中获取构造的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
并将其复制粘贴到浏览器中，我可以看到正确的JSON。
这是浏览器返回的JSON的代码段：
{"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},为什么代码无法从连接的输入流中获取/读取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
相关日志没有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
最佳答案
您在记录错误的内容：
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
Log.i(TAG,"doInBackground(), http response line:"+line);
当然，此时
line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的注释中的大量声明均不正确。即使URL是HTTPS URL，使用HttpURLConnection也是完全有效的，只要HttpsURLConnection扩展了HttpsURLConnection，只要您不需要HttpURLConnection的其他方法即可。
关于java - 无法使用Java的HttpURLConnection从Flickr API返回结果，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48601046/