提问人:kunal 提问时间:5/7/2018 最后编辑:kunal 更新时间:5/10/2018 访问量:263
具有 comet 处理器的此 URL 不支持 HTTP 方法 GET
HTTP method GET is not supported by this URL with comet processor
问:
这可能是一个可能的重复,但没有一个答案是有帮助的。
我有一个实现 CometProcessor 的 http servlet ,我已经参考了这个例子,并将 tomcat 连接器协议切换到非阻塞 io 。但是每次我尝试运行这个项目时,它都会给我
错误请帮忙
下面是我的Servlet(加上帮助程序类)和web.xml
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.catalina.CometEvent;
import org.apache.catalina.CometProcessor;
import com.sun.syndication.feed.synd.SyndEntry;
import com.sun.syndication.feed.synd.SyndFeed;
import com.sun.syndication.io.SyndFeedInput;
public class TomcatWeatherServlet extends HttpServlet implements CometProcessor {
private static final long serialVersionUID = 1L;
private Logger logger = Logger.getLogger(TomcatWeatherServlet.class.getName());
private MessageSender messageSender = null;
private static final Integer TIMEOUT = 60 * 1000;
@Override
public void destroy() {
messageSender.stop();
messageSender = null;
}
@Override
public void init() throws ServletException {
messageSender = new MessageSender();
Thread messageSenderThread = new Thread(messageSender,
"MessageSender[" + getServletContext().getContextPath() + "]");
messageSenderThread.setDaemon(true);
messageSenderThread.start();
}
public void event(final CometEvent event) throws IOException, ServletException {
HttpServletRequest request = event.getHttpServletRequest();
HttpServletResponse response = event.getHttpServletResponse();
if (event.getEventType() == CometEvent.EventType.BEGIN) {
request.setAttribute("org.apache.tomcat.comet.timeout", TIMEOUT);
logger.log(Level.INFO, "Begin for session: " + request.getSession(true).getId());
messageSender.setConnection(response);
Weatherman weatherman = new Weatherman(95118, 32408);
weatherman.start();
} else if (event.getEventType() == CometEvent.EventType.ERROR) {
logger.log(Level.INFO, "Error for session: " + request.getSession(true).getId());
event.close();
} else if (event.getEventType() == CometEvent.EventType.END) {
logger.log(Level.INFO, "End for session: " + request.getSession(true).getId());
event.close();
} else if (event.getEventType() == CometEvent.EventType.READ) {
throw new UnsupportedOperationException("This servlet does not accept data");
}
}
private class Weatherman {
private final List<URL> zipCodes;
private final String YAHOO_WEATHER = "http://weather.yahooapis.com/forecastrss?p=";
public Weatherman(Integer... zips) {
zipCodes = new ArrayList<URL>(zips.length);
for (Integer zip : zips) {
try {
zipCodes.add(new URL(YAHOO_WEATHER + zip));
} catch (Exception e) {
logger.log(Level.INFO, "weather man failed");
}
}
}
public void start() {
Runnable r = new Runnable() {
public void run() {
int i = 0;
while (i >= 0) {
int j = i % zipCodes.size();
SyndFeedInput input = new SyndFeedInput();
try {
InputStreamReader isr = new InputStreamReader(zipCodes.get(i).openStream());
SyndFeed feed = input.build(isr);
SyndEntry entry = (SyndEntry) feed.getEntries().get(0);
messageSender.send(entryToHtml(entry));
Thread.sleep(3000L);
} catch (Exception e) {
logger.log(Level.INFO, "start failed");
}
i++;
}
}
};
Thread t = new Thread(r);
t.start();
}
private String entryToHtml(SyndEntry entry) {
StringBuilder html = new StringBuilder("<h2>");
html.append(entry.getTitle());
html.append("</h2>");
html.append(entry.getDescription().getValue());
return html.toString();
}
}
private class MessageSender implements Runnable {
protected boolean running = true;
protected final ArrayList<String> messages = new ArrayList<String>();
private ServletResponse connection;
private synchronized void setConnection(ServletResponse connection) {
this.connection = connection;
notify();
}
public void stop() {
running = false;
}
/**
* Add message for sending.
*/
public void send(String message) {
synchronized (messages) {
messages.add(message);
logger.log(Level.INFO, "Message added #messages=" + messages.size());
messages.notify();
}
}
public void run() {
while (running) {
if (messages.size() == 0) {
try {
synchronized (messages) {
messages.wait();
}
} catch (InterruptedException e) {
logger.log(Level.INFO, e.getMessage());
}
}
String[] pendingMessages = null;
synchronized (messages) {
pendingMessages = messages.toArray(new String[0]);
messages.clear();
}
try {
if (connection == null) {
try {
synchronized (this) {
wait();
}
} catch (InterruptedException e) {
logger.log(Level.INFO, e.getMessage());
}
}
PrintWriter writer = connection.getWriter();
for (int j = 0; j < pendingMessages.length; j++) {
final String forecast = pendingMessages[j] + "<br>";
writer.println(forecast);
logger.log(Level.INFO, "Writing:" + forecast);
}
writer.flush();
writer.close();
connection = null;
logger.log(Level.INFO, "Closing connection");
} catch (IOException e) {
logger.log(Level.INFO, "IOExeption sending message", e);
}
}
}
}
}
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>WeatherServlet</servlet-name>
<servlet-class>servlet.TomcatWeatherServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>WeatherServlet</servlet-name>
<url-pattern>/Weather</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
答:
0赞
Christopher Schultz
5/10/2018
#1
你有几个问题,在这里。
首先,您尚未在 servlet 中实现该方法,这就是对该资源调用 GET 返回 405 响应的原因。当您使用常规 HTTP 调用时,您期望得到什么?doGet
GET /Weather
其次,Tomcat 在 8.5 中放弃了对 Comet 的支持,转而支持更标准的 WebSocket API。
因此,您根本无法将 Comet 与 Tomcat 9 一起使用。我很惊讶您甚至能够在 Tomcat 9 中初始化该 servlet。您必须从旧的 Tomcat 安装中获取一堆 JAR 文件才能使其甚至加载。但是,除非您降级到 Tomcat 8.0,否则它永远不会真正起作用。
你最好切换到 WebSocket。
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0赞
kunal
5/10/2018
你好。。据我对 Comet 编程的理解,上面的代码是事件驱动的,即一旦 servlet 初始化,它就会使用服务器端推送(因此不需要 doGet() IMO ) 所以预期的行为是,一旦 servlet 初始化,它将开始将数据推送到客户端,参见 WeatherMan 类。第二个是的,我后来意识到自 8.5 以来删除了对 Comet 支持的支持
0赞
Christopher Schultz
5/10/2018
Comet 确实是面向事件的,但您是在浏览器中发出普通的 HTTP 请求。您不能只在代码中键入代码并更改远程客户端与 Servlet 交互的方式。您的客户也必须知道该怎么做。implements CometProcessor
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