How do I handle time-outs and retries with jsoup connections?

Handling timeouts and retries with jsoup (a popular Java library for working with real-world HTML) involves setting appropriate timeout values and implementing a retry mechanism in case of connection failures. Here is how you can do both:

Handling Timeouts

When establishing a connection with jsoup, you can set a timeout value which determines how long jsoup will wait for the server to respond. If the server does not respond within the specified time, a SocketTimeoutException will be thrown. You can set the timeout using the timeout method, which takes an integer value representing the timeout duration in milliseconds.

Here's a simple example of setting a timeout:

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

public class JsoupTimeoutExample {
    public static void main(String[] args) {
        try {
            Document doc = Jsoup.connect("http://example.com")
                                .timeout(5000) // timeout set to 5 seconds
                                .get();
            System.out.println(doc.title());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

In this example, the timeout is set to 5 seconds (5000 milliseconds). If the connection takes longer than that, a SocketTimeoutException will be thrown.

Handling Retries

To handle retries, you can create a loop that attempts to connect multiple times before giving up. You can also implement an exponential backoff strategy to wait longer between each retry attempt. Here is a basic example:

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

public class JsoupRetryExample {
    public static final int MAX_RETRIES = 3;
    public static final int TIMEOUT = 5000;

    public static void main(String[] args) {
        int attempt = 0;
        boolean success = false;
        Document doc = null;

        while (attempt < MAX_RETRIES && !success) {
            try {
                doc = Jsoup.connect("http://example.com")
                           .timeout(TIMEOUT)
                           .get();
                success = true; // If we get here, the connection was successful
            } catch (Exception e) {
                attempt++;
                if (attempt < MAX_RETRIES) {
                    try {
                        // Exponential backoff (wait 2^attempt seconds before retrying)
                        Thread.sleep((long) Math.pow(2, attempt) * 1000);
                    } catch (InterruptedException ie) {
                        Thread.currentThread().interrupt();
                        throw new RuntimeException("Retry interrupted", ie);
                    }
                } else {
                    throw new RuntimeException("Connection failed after retries", e);
                }
            }
        }

        if (success) {
            System.out.println(doc.title());
        }
    }
}

In this example, the code tries to connect to the given URL with a timeout of 5 seconds. If the connection fails, it retries up to MAX_RETRIES times with an exponential backoff delay between each retry.

Keep in mind that when implementing retries, you should be careful not to overload the server with too many rapid attempts. Always use a backoff strategy and respect the server's constraints to avoid being blocked or causing service degradation.