Question

我正在使用com.sun.net.httpserver.HttpServer创建一个小容器来测试服务器代码的位数，并且无法让它使用多个线程来处理请求。

我调用java.util.concurrent.Executors.newFixedThreadPool（20）来创建一个包含20个线程的java.util.concurrent.ThreadPoolExecutor。然后，我在HttpServer上设置了这个Executor。使用Jmeter，我触发20个客户端线程，发送请求路由到服务器中唯一的HttpHandler实现。该处理程序执行System.out.println（this），我看到了这个输出：

Started TestServer at port 8800
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa
http.TestHandler@30eb9dfa

我以为我会在这里看到20个（或近20个）不同的线程。这是代码。

package http;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

public class TestServer implements Runnable {

    private final static int PORT    = Integer.getInteger("test.port", 8800); 
    private static TestServer serverInstance;
    private HttpServer        httpServer;
    private ExecutorService   executor;

    @Override
    public void run() {
        try {
            executor = Executors.newFixedThreadPool(20);

            httpServer = HttpServer.create(new InetSocketAddress(PORT), 0);
            httpServer.createContext("/test", new TestHandler());
            httpServer.setExecutor(executor);
            httpServer.start();
            System.out.println("Started TestServer at port " + PORT);

            // Wait here until notified of shutdown.
            synchronized (this) {
                try {
                    this.wait();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

    static void shutdown() {

        try { 
            System.out.println("Shutting down TestServer.");            
            serverInstance.httpServer.stop(0);

        } catch (Exception e) {
            e.printStackTrace();
        }

        synchronized (serverInstance) {
            serverInstance.notifyAll();
        }

    }

    public static void main(String[] args) throws Exception {

        serverInstance = new TestServer();

        Thread serverThread = new Thread(serverInstance);
        serverThread.start();

        Runtime.getRuntime().addShutdownHook(new OnShutdown());

        try {
            serverThread.join();
        } catch (Exception e) { }
    }

}

/* Responds to the /test URI. */
class TestHandler implements HttpHandler {

    boolean debug = Boolean.getBoolean("test.debug");

    public void handle(HttpExchange exchange) throws IOException {

        System.out.println(this);  // ALWAYS SAME THREAD!

        String response = "RESPONSE AT " + System.currentTimeMillis();

        exchange.sendResponseHeaders(200, response.length());
        OutputStream os = exchange.getResponseBody();
        os.write(response.getBytes());
        os.flush();
        os.close();
    }
}

/* Responds to a JVM shutdown by stopping the server. */
class OnShutdown extends Thread {
    public void run() {
        TestServer.shutdown();
    }
}

我希望HttpServer并行创建多个TestHandler来为多个同时请求提供服务。我在这里缺少什么？

（顺便说一句，这与Can I make a Java HttpServer threaded/process requests in parallel?非常相似，但答案是使用Executor，我已经在做了。谢谢。）

Answer 1

可以在不同的线程中多次运行runnable的相同实例。有关详细信息，请参阅Initializing two threads with the same instance of a runnable。

您在示例中打印的是HttpHandler信息，但没有关于在哪个线程中运行的信息。并且该信息不会更改，因为服务器始终为所有线程重用相同的对象。

如果要打印线程ID，可以使用：

long threadId = Thread.currentThread().getId();
System.out.println(threadId);

threadId应该按预期更改。

如何让HttpServer并行创建多个HttpHandler？

1 个答案: