Title here
Summary here
Context in Miranda
Here’s the translation of the Go code to Java, formatted in Markdown suitable for Hugo:
Our first program 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 ContextServlet 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");
new Thread(() -> {
try {
TimeUnit.SECONDS.sleep(10);
if (asyncContext.getRequest().isAsyncStarted()) {
PrintWriter writer = asyncContext.getResponse().getWriter();
writer.println("hello");
asyncContext.complete();
}
} catch (InterruptedException e) {
System.out.println("server: " + e.getMessage());
} catch (IOException e) {
System.out.println("server: Error writing response: " + e.getMessage());
} finally {
System.out.println("server: hello handler ended");
}
}).start();
// Simulate cancellation after 5 seconds
new Thread(() -> {
try {
TimeUnit.SECONDS.sleep(5);
if (asyncContext.getRequest().isAsyncStarted()) {
asyncContext.complete();
System.out.println("server: context canceled");
}
} catch (InterruptedException e) {
System.out.println("server: " + e.getMessage());
}
}).start();
}
}In this Java version, we use a Servlet with asynchronous support to simulate the behavior of the Go example. The AsyncContext is used to manage the lifecycle of the asynchronous operation, similar to how context.Context is used in Go.
The servlet starts two threads:
- One that waits for 10 seconds before sending a response.
- Another that simulates cancellation after 5 seconds.
If the cancellation occurs before the response is sent, the AsyncContext is completed, effectively cancelling the operation.
To run this servlet, you would need to deploy it to a servlet container like Tomcat or Jetty. The exact steps for deployment and running would depend on your specific setup.
This example demonstrates how to handle long-running operations in a web server context, with the ability to cancel the operation if needed. While Java doesn’t have a direct equivalent to Go’s context.Context, the AsyncContext in servlets provides similar functionality for managing the lifecycle of asynchronous operations.