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从URL解析JSON

有没有最简单的方法来从URL解析JSON?我使用Gson找不到任何有用的示例。

40
Peril
  1. 首先,您需要下载URL(作为文本):

    private static String readUrl(String urlString) throws Exception {
        BufferedReader reader = null;
        try {
            URL url = new URL(urlString);
            reader = new BufferedReader(new InputStreamReader(url.openStream()));
            StringBuffer buffer = new StringBuffer();
            int read;
            char[] chars = new char[1024];
            while ((read = reader.read(chars)) != -1)
                buffer.append(chars, 0, read); 
    
            return buffer.toString();
        } finally {
            if (reader != null)
                reader.close();
        }
    }
    
  2. 然后您需要解析它(这里有一些选择)。

    • GSON(完整示例):

      static class Item {
          String title;
          String link;
          String description;
      }
      
      static class Page {
          String title;
          String link;
          String description;
          String language;
          List<Item> items;
      }
      
      public static void main(String[] args) throws Exception {
      
          String json = readUrl("http://www.javascriptkit.com/"
                                + "dhtmltutors/javascriptkit.json");
      
          Gson gson = new Gson();        
          Page page = gson.fromJson(json, Page.class);
      
          System.out.println(page.title);
          for (Item item : page.items)
              System.out.println("    " + item.title);
      }
      

      输出:

      javascriptkit.com
          Document Text Resizer
          JavaScript Reference- Keyboard/ Mouse Buttons Events
          Dynamically loading an external JavaScript or CSS file
      
    • 尝试从 json.org _:的Java AP​​I

      try {
          JSONObject json = new JSONObject(readUrl("..."));
      
          String title = (String) json.get("title");
          ...
      
      } catch (JSONException e) {
          e.printStackTrace();
      }
      
66
dacwe

GSON 具有一个生成器 Reader 对象:fromJson(Reader json,Class classOfT)

这意味着您可以从URL创建Reader,然后将其传递给Gson以使用流并进行反序列化。

三行相关代码。

import Java.io.InputStreamReader;
import Java.net.URL;
import Java.util.Map;

import com.google.gson.Gson;

public class GsonFetchNetworkJson {

    public static void main(String[] ignored) throws Exception {

        URL url = new URL("https://httpbin.org/get?color=red&shape=oval");
        InputStreamReader reader = new InputStreamReader(url.openStream());
        MyDto dto = new Gson().fromJson(reader, MyDto.class);

        // using the deserialized object
        System.out.println(dto.headers);
        System.out.println(dto.args);
        System.out.println(dto.Origin);
        System.out.println(dto.url);
    }

    private class MyDto {
        Map<String, String> headers;
        Map<String, String> args;
        String Origin;
        String url;
    }
}

如果碰巧在端点上获得了403错误代码,该端点在其他情况下也可以正常工作(例如,与curl或其他客户端一起使用),则可能的原因可能是端点期望User-Agent标头,默认情况下为Java URLConnection尚未设置。一个简单的解决方法是在文件顶部添加例如System.setProperty("http.agent", "Netscape 1.0");

11
ccpizza

您可以使用org.Apache.commons.io.IOUtils进行下载,并使用org.json.JSONTokener进行解析:

JSONObject jo = (JSONObject) new JSONTokener(IOUtils.toString(new URL("http://gdata.youtube.com/feeds/api/videos/SIFL9qfmu5U?alt=json"))).nextValue();
System.out.println(jo.getString("version"));
9
Stefan Schramm
public static TargetClassJson downloadPaletteJson(String url) throws IOException {
        if (StringUtils.isBlank(url)) {
            return null;
        }
        String genreJson = IOUtils.toString(new URL(url).openStream());
        return new Gson().fromJson(genreJson, TargetClassJson.class);
    }
1
yazabara

这是一个简单的方法。

首先从网址解析JSON-

public String readJSONFeed(String URL) {
    StringBuilder stringBuilder = new StringBuilder();
    HttpClient httpClient = new DefaultHttpClient();
    HttpGet httpGet = new HttpGet(URL);

    try {

        HttpResponse response = httpClient.execute(httpGet);
        StatusLine statusLine = response.getStatusLine();
        int statusCode = statusLine.getStatusCode();

        if (statusCode == 200) {

            HttpEntity entity = response.getEntity();
            InputStream inputStream = entity.getContent();
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(inputStream));
            String line;
            while ((line = reader.readLine()) != null) {
                stringBuilder.append(line);
            }

            inputStream.close();

        } else {
            Log.d("JSON", "Failed to download file");
        }
    } catch (Exception e) {
        Log.d("readJSONFeed", e.getLocalizedMessage());
    }
    return stringBuilder.toString();
}

然后放置一个任务,然后从JSON中读取所需的值-

private class ReadPlacesFeedTask extends AsyncTask<String, Void, String> {
    protected String doInBackground(String... urls) {

        return readJSONFeed(urls[0]);
    }

    protected void onPostExecute(String result) {

        JSONObject json;
        try {
            json = new JSONObject(result);

        ////CREATE A JSON OBJECT////

        JSONObject data = json.getJSONObject("JSON OBJECT NAME");

        ////GET A STRING////

        String title = data.getString("");

        //Similarly you can get other types of data
        //Replace String to the desired data type like int or boolean etc.

        } catch (JSONException e1) {
            e1.printStackTrace();

        }

        //GETTINGS DATA FROM JSON ARRAY//

        try {

            JSONObject jsonObject = new JSONObject(result);
            JSONArray postalCodesItems = new JSONArray(
                    jsonObject.getString("postalCodes"));

                JSONObject postalCodesItem = postalCodesItems
                        .getJSONObject(1);

        } catch (Exception e) {
            Log.d("ReadPlacesFeedTask", e.getLocalizedMessage());
        }
    }
}

然后,您可以放置​​这样的任务-

new ReadPlacesFeedTask()
    .execute("JSON URL");
1
Confuse
 import org.Apache.commons.httpclient.util.URIUtil;
 import org.Apache.commons.io.FileUtils;
 import groovy.json.JsonSlurper;
 import Java.io.File;

    tmpDir = "/defineYourTmpDir"
    URL url = new URL("http://yourOwnURL.com/file.json");
    String path = tmpDir + "/tmpRemoteJson" + ".json";
    remoteJsonFile = new File(path);
    remoteJsonFile.deleteOnExit(); 
    FileUtils.copyURLToFile(url, remoteJsonFile);
    String fileTMPPath = remoteJsonFile.getPath();

    def inputTMPFile = new File(fileTMPPath);
    remoteParsedJson = new JsonSlurper().parseText(inputTMPFile.text);
0
Rami Sharaiyri

我将Java 1.8与com.fasterxml.jackson.databind.ObjectMapper一起使用

ObjectMapper mapper = new ObjectMapper();
Integer      value = mapper.readValue(new URL("your url here"), Integer.class);

Integer.class也可以是复杂类型。仅作为示例。

0
Ecreators