Can jsoup be used in a multithreaded application?

Yes, jsoup can be used in a multithreaded application. Jsoup is a Java HTML parser library designed to handle and manipulate HTML documents, and it is thread-safe when used in a way that avoids shared mutable state between threads.

When using jsoup in a multithreaded environment, you should consider the following guidelines to ensure thread safety:

1. Avoid Shared State: Each thread should work with its own separate Document object. Avoid sharing a Document or any other mutable jsoup objects between threads unless they are only being read and not modified.

2. Immutable Once Built: Once you have built a Document using jsoup, it is safe to read from multiple threads concurrently, as long as you do not modify it. If you need to make changes, you should do so in a thread-safe manner, such as synchronizing access or using thread-local instances.

3. Thread Confinement: Keep the parsing and manipulation of a Document within the same thread. If you need to pass a Document or elements to another thread, ensure that no further modifications will be made to it.

4. Thread-Local Storage: If you have data or configurations that need to be reused across multiple parses/operations within the same thread, consider using thread-local storage to store instances of Parser or other configurations.

Here is an example of how to use jsoup in a multithreaded application in Java:

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

public class JsoupMultithreadedExample {

    private static final String URL = "http://example.com";

    public static void main(String[] args) {
        // Create a Runnable task for fetching and parsing HTML
        Runnable task = () -> {
            try {
                // Each thread has its own Document instance
                Document document = Jsoup.connect(URL).get();

                // Perform thread-safe operations on the document
                String title = document.title();
                System.out.println(Thread.currentThread().getName() + ": " + title);
            } catch (Exception e) {
                e.printStackTrace();
            }
        };

        // Start multiple threads, each will fetch and parse the HTML independently
        for (int i = 0; i < 5; i++) {
            Thread thread = new Thread(task);
            thread.start();
        }
    }
}

In this example, each thread fetches and parses the HTML document from a given URL independently. Since each thread operates on its own Document object, there are no thread-safety issues.

Always remember that while jsoup's data structures are not inherently thread-safe, correct usage patterns can make your jsoup-based application work correctly in a multithreaded context. If your application requires shared mutable state, you'll need to implement your own synchronization mechanisms to ensure thread safety.