程序化 ServerEndpoint 在嵌入式 Tomcat 中不起作用

Question

我有一个嵌入式 tomcat 正在运行，我正在尝试以编程方式设置 websocket，但不能使用注释，因为我动态获取上下文路径列表。使用 Java 8 和 Tomcat 7。

下面是我正在使用的代码，

嵌入式Tomcat，

public class EmbeddedTomcat {
/**
 * @param args
 * @throws LifecycleException 
 */
public static void main(String[] args) throws LifecycleException {
    Tomcat tomcat = new Tomcat();
    tomcat.setPort(5555);

    Context ctx = tomcat.addContext("", new File(".").getAbsolutePath());

    Tomcat.addServlet(ctx, "hello", new HttpServlet() {
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) 
                throws ServletException, IOException {
            Writer w = resp.getWriter();
            w.write("Hello World !!");
            w.flush();
            w.close();
        }
    });

    ctx.addServletMapping("/hello", "hello");

    ctx.addApplicationListener(WSContextListener.class.getName());

    tomcat.start();
    tomcat.getServer().await();
}

}

WebSocket 监听器动态添加端点，

public class WSContextListener extends WsContextListener {

@Override
public void contextInitialized(ServletContextEvent sce) {
    super.contextInitialized(sce);

    ServerContainer sc =
            (ServerContainer) sce.getServletContext().getAttribute(
                    Constants.SERVER_CONTAINER_SERVLET_CONTEXT_ATTRIBUTE);
    try {
        ServerEndpointConfig endPointConfig = ServerEndpointConfig.Builder
                .create(WSEndpoint.class, "/wshello")
                .build();
        sc.addEndpoint(endPointConfig);
    } catch(DeploymentException de) {
        de.printStackTrace();
    }
}

}

实际的服务器端点类，

public class WSEndpoint extends Endpoint {

/* (non-Javadoc)
 * @see javax.websocket.Endpoint#onOpen(javax.websocket.Session, javax.websocket.EndpointConfig)
 */
@Override
public void onOpen(Session session, EndpointConfig endpointConfig) {
    System.out.println(String.format("Opened a new session with Id[%s] associated to endpoint[%s]", session.getId(), session.getRequestURI().getPath()));

    session.addMessageHandler(new MessageHandler.Whole<String>() {
        @Override
        public void onMessage(String data) {
            System.out.println("Data received - " + data);
            session.getAsyncRemote().sendText(data);
        }
    });
}

@Override
public void onClose(Session session, CloseReason closeReason) {
    System.out.println(String.format("Closing the connection to endpoint[%s] for session Id[%s] ", session.getRequestURI().getPath(), session.getId()));
    super.onClose(session, closeReason);
}

@Override
public void onError(Session session, Throwable throwable) {
    System.out.println(String.format("Error [%s] occurred on session Id[%s] associated to endpoint[%s]", throwable.getMessage(), session.getId(), session.getRequestURI().getPath()));
    super.onError(session, throwable);
}

}

最后，连接到 Websocket 的 javascript 位，

var webSocket = new WebSocket("ws://localhost:5555/wshello");

我可以访问 servlet (http://localhost:5555/hello) 并且该位有效。当我尝试通过上面的 javascript 代码访问 websocket 时，它失败了，

websocket_test.html:18 WebSocket 连接到“ws://localhost:5555/wshello”失败：WebSocket 握手期间出错：意外响应代码：404

Answer 1

试试这个

var webSocket = new WebSocket("ws://localhost:5555/hello", "protocol");

添加到客户端处理 websocket 的协议（可选）。 删除 wshello "ws"