Why Does My Java Program Get a 403 Forbidden Error When Scraping Google Search Results While My Browser Doesn't?

Java Program Receiving 403 Forbidden Error While Web Browsers Succeed

Problem:

A Java program designed to retrieve the result count for a given Google search query returns a 403 Forbidden error, while the same query yields results in web browsers. Code snippet:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;

public class DataGetter {

    public static void main(String[] args) throws IOException {
        getResultAmount("test");
    }

    private static int getResultAmount(String query) throws IOException {
        BufferedReader r = new BufferedReader(new InputStreamReader(new URL("https://www.google.com/search?q=" + query).openConnection()
                .getInputStream()));
        String line;
        String src = "";
        while ((line = r.readLine()) != null) {
            src += line;
        }
        System.out.println(src);
        return 1;
    }

}

Error:

Exception in thread "main" java.io.IOException: Server returned HTTP response code: 403 for URL: https://www.google.com/search?q=test
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
    at DataGetter.getResultAmount(DataGetter.java:15)
    at DataGetter.main(DataGetter.java:10)

Solution:

The issue arises because Java's URLConnection class does not fake an actual user-agent by default. Modifying the code to set a user-agent header resolves this problem:

URLConnection connection = new URL("https://www.google.com/search?q=" + query).openConnection();
connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11");
connection.connect();

BufferedReader r = new BufferedReader(new InputStreamReader(connection.getInputStream(), Charset.forName("UTF-8")));

Additionally, SSL handling is transparent, as indicated by the exception stacktrace.

Further Considerations:

Retrieving result counts involves further steps, including faking a browser by fetching cookies and parsing redirect token links:

String cookie = connection.getHeaderField("Set-Cookie").split(";")[0];
Pattern pattern = Pattern.compile("content=\\"0;url=(.*?)\\"");
Matcher m = pattern.matcher(response);
if (m.find()) {
    String url = m.group(1);
    connection = new URL(url).openConnection();
    connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11");
    connection.setRequestProperty("Cookie", cookie);
    connection.connect();
    r = new BufferedReader(new InputStreamReader(connection.getInputStream(), Charset.forName("UTF-8")));
    sb = new StringBuilder();
    while ((line = r.readLine()) != null) {
        sb.append(line);
    }
    response = sb.toString();
    pattern = Pattern.compile("<div><p>Executing this full code yields a result of 2930000000L.</p></div>

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