Context in CLIPS

Here’s the translation of the Go code to Java, with explanations in Markdown format suitable for Hugo:

Our example demonstrates the usage of Context for controlling cancellation in an HTTP server. A Context carries deadlines, cancellation signals, and other request-scoped values across API boundaries and threads.

import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.TimeUnit;
import javax.servlet.AsyncContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns = "/hello", asyncSupported = true)
public class ContextExample extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        
        AsyncContext asyncContext = request.startAsync();
        asyncContext.setTimeout(30000); // 30 seconds timeout

        System.out.println("server: hello handler started");

        asyncContext.start(() -> {
            try {
                TimeUnit.SECONDS.sleep(10);
                PrintWriter out = asyncContext.getResponse().getWriter();
                out.println("hello");
                asyncContext.complete();
            } catch (InterruptedException e) {
                System.out.println("server: " + e.getMessage());
                asyncContext.getResponse().setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
                asyncContext.complete();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                System.out.println("server: hello handler ended");
            }
        });
    }
}

In this Java servlet:

1. We use the AsyncContext to simulate the behavior of Go’s context.Context. It allows us to handle long-running operations asynchronously.

2. The AsyncContext is created for each request, similar to how context.Context is created in Go.

3. We set a timeout of 30 seconds on the AsyncContext, which is analogous to setting a deadline on a context in Go.

4. The long-running operation (simulated by TimeUnit.SECONDS.sleep(10)) is executed in a separate thread.

5. If the operation completes successfully, it writes “hello” to the response.

6. If the operation is interrupted (which could happen if the client disconnects or the timeout is reached), we catch the InterruptedException and set an error status.

7. Finally, we always print “server: hello handler ended”, simulating the deferred print statement in the Go code.

To run this servlet, you would need to deploy it to a servlet container like Tomcat or Jetty. The exact steps for deployment would depend on your specific setup.

This Java implementation provides similar functionality to the Go example, demonstrating how to handle long-running operations in an HTTP server while being responsive to cancellation or timeout.