Parsing JSON from URL

Question

Is there any simplest way to parse JSON from a URL? I used Gson I can't find any helpful examples.

for example it will be like this http://gdata.youtube.com/feeds/api/videos/SIFL9qfmu5U?alt=json or from facebook graph — Peril, Sep 19 '11 at 07:24

score 70 · Accepted Answer · edited Oct 17 '14 at 23:28

First you need to download the URL (as text):

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();
    }
}

Then you need to parse it (and here you have some options).

GSON (full example):

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);
}

Outputs:

javascriptkit.com
    Document Text Resizer
    JavaScript Reference- Keyboard/ Mouse Buttons Events
    Dynamically loading an external JavaScript or CSS file

Try the java API from json.org:

try {
    JSONObject json = new JSONObject(readUrl("..."));

    String title = (String) json.get("title");
    ...

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

'java' tag indicates that he doesn't want to use javascript. — Peter Štibraný, Sep 19 '11 at 07:25
This will MANGLE the JSON and produce parsing-errors. Its completely unnecessary to build your own string from the received contents of a URL, GSON supports reading from BufferedReader directly. THIS EXAMPLE WILL NOT WORK IN EVERY CASE — specializt, Jan 07 '15 at 14:07
Needs to be updated. Link is broken and it's unclear what should replace the final "..." — Hack-R, Mar 11 '16 at 19:46

ccpizza · Answer 2 · 2023-04-19T14:04:57.993

GSON has a builder that takes a Reader object: fromJson(Reader json, Class<T> classOfT).

This means you can create a Reader from a URL and then pass it to Gson to consume the stream and do the deserialisation.

Only three lines of relevant code.

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;
    }
}

^{If you happen to get a 403 error code with an endpoint which otherwise works fine (e.g. with curl or other clients) then a possible cause could be that the endpoint expects a User-Agent header and by default Java URLConnection is not setting it. An easy fix is to add at the top of the file e.g. System.setProperty("http.agent", "Netscape 1.0");.}

Maven dependency

<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

Gradle dependency

implementation 'com.google.code.gson:gson:2.10.1'

@Sundar: for arrays you'd use TypeToken: https://stackoverflow.com/a/10292824/191246 — ccpizza, Aug 19 '17 at 08:29

score 10 · Answer 3 · answered Jan 21 '14 at 20:08

10

You could use org.apache.commons.io.IOUtils for downloading and org.json.JSONTokener for parsing:

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"));

answered Jan 21 '14 at 20:08

Stefan Schramm

144
1
3

2

I think you have to add `.openStream()` after `new URL(...)`. So it has to look like this: `JSONObject jo = (JSONObject) new JSONTokener(IOUtils.toString(new URL("http://gdata.youtube.com/feeds/api/videos/SIFL9qfmu5U?alt=json").openStream())).nextValue();` – Selphiron Dec 27 '15 at 20:20
@ Selphiron, Working perfectly. Thanks a lot. – mahi Aug 31 '16 at 08:59

score 1 · Answer 4 · answered Sep 21 '14 at 04:30

Here is a easy method.

First parse the JSON from url -

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();
}

Then place a task and then read the desired value from JSON -

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());
        }
    }
}

You can then place a task like this -

new ReadPlacesFeedTask()
    .execute("JSON URL");

score 1 · Answer 5 · answered Oct 15 '15 at 08:12

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);
    }

Rami Sharaiyri · Answer 6 · 2015-08-20T15:30:48.717

 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);

score 0 · Answer 7 · answered Sep 06 '17 at 21:03

I use java 1.8 with com.fasterxml.jackson.databind.ObjectMapper

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

Integer.class can be also a complex type. Just for example used.

score -7 · Answer 8 · edited Feb 07 '17 at 08:11

-7

A simple alternative solution:

Paste the URL into a json to csv converter
Open the CSV file in either Excel or Open Office
Use the spreadsheet tools to parse the data

edited Feb 07 '17 at 08:11

canadiancreed

1,966
6
41
58

answered Mar 26 '15 at 10:38

gareth

1

3

This is a very low quality answer. I don't think that using Excel is a complex solution to this problem. – Piotr Dajlido Mar 26 '15 at 10:46
promoting a json to csv converter maybe? – zundi Jan 29 '16 at 20:51

Parsing JSON from URL

8 Answers8

Maven dependency

Gradle dependency

Linked

Related