Jsoup reddit scraper 429 error

Question

So I'm trying to use jsoup to scrape Reddit for images, but when I scrape certain subreddits such as /r/wallpaper, I get a 429 error and am wondering how to fix this. Totally understand that this code is horrible and this is a pretty noob question, but I'm completely new to this. Anyways:

import java.io.IOException;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import java.io.*;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jsoup.Jsoup;

import org.jsoup.nodes.Attributes;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import java.io.IOException;
import java.net.URL;
import java.util.Scanner;

public class javascraper{

public static void main (String[]args) throws MalformedURLException
{
    Scanner scan = new Scanner (System.in);
    System.out.println("Where do you want to store the files?");
    String folderpath = scan.next();
    System.out.println("What subreddit do you want to scrape?");
    String subreddit = scan.next();
    subreddit = ("http://reddit.com/r/" + subreddit);
    new File(folderpath + "/" + subreddit).mkdir();

    //test

    try{
        //gets http protocol
        Document doc = Jsoup.connect(subreddit).timeout(0).get();

        //get page title
        String title = doc.title();
        System.out.println("title : " + title);

        //get all links
        Elements links = doc.select("a[href]");

        for(Element link : links){

            //get value from href attribute
            String checkLink = link.attr("href");
            Elements images = doc.select("img[src~=(?i)\\.(png|jpe?g|gif)]");
            if (imgCheck(checkLink)){ // checks to see if img link j
                System.out.println("link : " + link.attr("href"));
                downloadImages(checkLink, folderpath);
            }
        }
    }
    catch (IOException e){
        e.printStackTrace();
    }
}

public static boolean imgCheck(String http){
    String png = ".png";
    String jpg = ".jpg";
    String jpeg = "jpeg"; // no period so checker will only check last four characaters
    String gif = ".gif";
    int length = http.length();

    if (http.contains(png)|| http.contains("gfycat") || http.contains(jpg)|| http.contains(jpeg) || http.contains(gif)){
        return true;
    }
    else{
        return false;
    }
}

private static void downloadImages(String src, String folderpath) throws IOException{
    String folder = null;

    //Exctract the name of the image from the src attribute

    int indexname = src.lastIndexOf("/");

    if (indexname == src.length()) {
        src = src.substring(1, indexname);
    }
    indexname = src.lastIndexOf("/");

    String name = src.substring(indexname, src.length());

    System.out.println(name);

    //Open a URL Stream

    URL url = new URL(src);

    InputStream in = url.openStream();

    OutputStream out = new BufferedOutputStream(new FileOutputStream( folderpath+ name));

    for (int b; (b = in.read()) != -1;) {

        out.write(b);

    }

    out.close();

    in.close();
}

}

Answer 1

Your issue is caused by the fact that your scraper is violating reddit's API rules. Error 429 means "Too many requests" – you're requesting too many pages too fast.

You can make one request every 2 seconds, and you also need to set a proper user agent (they format they recommend is <platform>:<app ID>:<version string> (by /u/<reddit username>)). The way it currently looks, your code is running too fast and doesn't specify one, so it's going to be severely rate-limited.

---

To fix it, first off, add this to the start of your class, before the main method:

public static final String USER_AGENT = "<PUT YOUR USER AGENT HERE>";

(Make sure to specify an actual user agent).

Then, change this (in downloadImages)

URL url = new URL(src);
InputStream in = url.openStream();

to this:

URLConnection connection = (new URL(src)).openConnection();

Thread.sleep(2000); //Delay to comply with rate limiting
connection.setRequestProperty("User-Agent", USER_AGENT);

InputStream in = connection.getInputStream();

You'll also want to change this (in main)

Document doc = Jsoup.connect(subreddit).timeout(0).get();

to this:

Document doc = Jsoup.connect(subreddit).userAgent(USER_AGENT).timeout(0).get();

Then your code should stop running into that error.

---

Note that using reddit's API (IE, /r/subreddit.json instead of /r/subreddit) would probably make this project easier, but it isn't required and your current code will work.