我试图使用 Servlet API 3 中定义的异步处理来实现 COMET 聊天。它不起作用 - 聊天被阻止,所以我创建了调试 servlet 来仅测试异步部分。
这是我的 doGet 方法:
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
log.debug("doGet called");
int timeout = 30 + RandomUtils.nextInt(60);
String message = RandomStringUtils.randomAlphanumeric(50 + RandomUtils.nextInt(250));
response.setHeader("Access-Control-Allow-Origin", "*");
final AsyncContext context = request.startAsync();
synchronized(items) {
items.add(new RequestItem(context, message, timeout));
}
log.debug("doGet created request and finished");
}
我将请求项目放入队列中,并且有一个线程正在运行,它将在指定超时后获取项目并将响应发送到 AsyncContext,打印有关它的消息。问题是,线程被阻塞,直到 AsyncContext 得到响应。这是在浏览器中请求 4 个页面加载后在我的日志中可见的内容:
2011-12-08 13:56:36,923 DEBUG [my.servlet.TestAsyncServlet] doGet called
2011-12-08 13:56:36,952 DEBUG [my.servlet.TestAsyncServlet] doGet created request and finished
2011-12-08 13:57:39,934 TRACE [my.servlet.TestAsyncServlet] respond on item RequestItem [context=org.apache.catalina.core.AsyncContextImpl@175870a, message=zEQpATavzwFl6qIbBKve4OzIY9UUuZBwbqN1TC5KpU3i8LM9B6ChgUqaRmcT2yF, timeout=0]
2011-12-08 13:57:39,962 DEBUG [my.servlet.TestAsyncServlet] doGet called
2011-12-08 13:57:39,962 DEBUG [my.servlet.TestAsyncServlet] doGet created request and finished
2011-12-08 13:58:53,949 TRACE [my.servlet.TestAsyncServlet] respond on item RequestItem [context=org.apache.catalina.core.AsyncContextImpl@88ee03, message=pKHKC632CPIk7hGLV0YqCbQl1qpWIoyNv5OWCp21bEqoni1gbY79HT61QEUS2eCjeTMoNEwdqKzCZNGgDngULysSzVdzFTnQQ5cQ8JvcYnp1pLVqGTueJPWnbRdUuO, timeout=0]
2011-12-08 13:58:53,960 DEBUG [my.servlet.TestAsyncServlet] doGet called
2011-12-08 13:58:53,960 DEBUG [my.servlet.TestAsyncServlet] doGet created request and finished
2011-12-08 13:59:36,954 TRACE [my.servlet.TestAsyncServlet] respond on item RequestItem [context=org.apache.catalina.core.AsyncContextImpl@197950e, message=43FPeEUZWBLqgkAqS3WOFMiHUMVvx6o4jNqWLx8kUvwxqJqpOZyGCtiIcr7yw, timeout=0]
2011-12-08 13:59:36,999 DEBUG [my.servlet.TestAsyncServlet] doGet called
2011-12-08 13:59:36,999 DEBUG [my.servlet.TestAsyncServlet] doGet created request and finished
2011-12-08 14:00:34,957 TRACE [my.servlet.TestAsyncServlet] respond on item RequestItem [context=org.apache.catalina.core.AsyncContextImpl@1cb1278, message=r69Y4NQsyR1vj0kzUlHssic2x1Yrr6T09IGKjWAH1E6Lz4VhFTy9dQHi5CPeTObyjLLBDlCLEDfiyMUnVkVIEgYG7r47Ak4w30RklhzdEi9nthqdfNkry6nyjircsFPX534NqWjI1LwsrGq5nOa3ZYtfjfPVpGlk4KDmWP11L53YntO3GmptZPKa50gcqj9i, timeout=0]
正如所见,下一个 doGet 方法仅在前一个请求(理论上是异步的)应答后才被调用。所以整个异步事情根本不起作用!这是 web.xml 声明:
<servlet>
<servlet-name>TestAsyncServlet</servlet-name>
<servlet-class>my.servlet.TestAsyncServlet</servlet-class>
<async-supported>true</async-supported>
</servlet>
<servlet-mapping>
<servlet-name>TestAsyncServlet</servlet-name>
<url-pattern>/test-async</url-pattern>
</servlet-mapping>
我正在尽一切可能在互联网上找到。我看不出犯错的地方。我发现在 servlet.xml 中配置没有什么特别之处。所以问题是,为什么它不能正常工作?