Tomcat 7异步处理

您正在混淆不同的概念。您必须区分：

1. 根据Servlet 3.0的异步请求处理 ；一个使您能够将传入的Servlet请求与Web容器线程池分离的API。它不会动态创建任何线程。界面的用户可以实施适当的多线程解决方案。它与非阻塞IO不相关。
2. 线程池 ; 提供了一种获取和管理Web容器中的线程的机制。对于 异步请求处理， 您有2个选择。您可以定义自己的文件

   ExecutorService

   并使用它来进一步处理请求，也可以创建新文件

   Runnable

   并

   AsyncContext

   通过调用将其提交给获得的文件

   AsyncContext.start()

   。对于Tomcat，后一种方法使用中定义的Tomcat线程池

   server.xml

   。
3. 非阻塞IO（NIO） ；尽管它也是 异步的 ，但情况有所不同。它涉及非阻塞IO操作，例如磁盘或网络IO。如果要为HTTP请求处理启用NIO，请查看Tomcat的文档。

下面的示例概述了它 如何 工作。它仅使用一个线程进行工作者作业。如果您从2个不同的浏览器并行运行它，则输出如下所示（我使用自定义记录器）：

   DATE   THREAD_ID  LEVEL      MESSAGE2011-09-03 11:51:22.198 +0200      26        I:     >doGet: chrome2011-09-03 11:51:22.204 +0200      26        I:     <doGet: chrome2011-09-03 11:51:22.204 +0200      28        I:     >run: chrome2011-09-03 11:51:27.908 +0200      29        I:     >doGet: firefox2011-09-03 11:51:27.908 +0200      29        I:     <doGet: firefox2011-09-03 11:51:32.227 +0200      28        I:     <run: chrome2011-09-03 11:51:32.228 +0200      28        I:     >run: firefox2011-09-03 11:51:42.244 +0200      28        I:     <run: firefox

您会看到

doGet

http://localhost:8080/pc/TestServlet?name=chrome

http://localhost:8080/pc/TestServlet?name=firefox

简单示例Servlet

@WebServlet(asyncSupported = true, value = "/TestServlet", loadonStartup = 1)public class TestServlet extends HttpServlet {    private static final Logger LOG = Logger.getLogger(TestServlet.class.getName());    private static final long serialVersionUID = 1L;    private static final int NUM_WORKER_THREADS = 1;    private ExecutorService executor = null;    @Override    public void init() throws ServletException {        this.executor = Executors.newFixedThreadPool(NUM_WORKER_THREADS);    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        final String name = request.getParameter("name");        LOG.info(">doGet: " + name);        AsyncContext ac = request.startAsync(); // obtain async context        ac.setTimeout(0); // test only, no timeout                Runnable worker = new TestWorker(name, ac);                this.executorService.execute(worker);                // ac.start(worker);        LOG.info("<doGet: " + name);    }}

…以及TestWorker

public class TestWorker implements Runnable {    private static final Logger LOG = Logger.getLogger(TestWorker.class.getName());    private final String name;    private final AsyncContext context;    private final Date queued;    public TestWorker(String name, AsyncContext context) {        this.name = name;        this.context = context;        this.queued = new Date(System.currentTimeMillis());    }    @Override    public void run() {        LOG.info(">run: " + name);                for (int i = 0; i < 100; i++) { try {     Thread.sleep(100); } catch (InterruptedException e) {     throw new RuntimeException(e); }        }        ServletResponse response = this.context.getResponse();        response.setContentType("text/plain");        try { PrintWriter out = response.getWriter(); out.println("Name:tt" + this.name); out.println("Queued:tt" + this.queued); out.println("End:tt" + new Date(System.currentTimeMillis())); out.println("Thread:tt" + Thread.currentThread().getId()); out.flush();        } catch (IOException e) { throw new RuntimeException(e);        }        this.context.complete();        LOG.info("<run: " + name);    }}