Exception running a simple websocket with Camel component on Jetty

1
votes

I'm trying to run use Camel Websocket component on Jetty but cannot get rid of the following exception. I'm not sure if this a issue with Jetty running with Camel or issues with versions compatibility or something is missing in my code.

I've put the project on Github in case someone wants to give it a try. https://github.com/soumyasd/jettycamelwebsocket

Following are the steps to run the application.

  1. Update your Twitter credentials in this class src/main/java/demo/websocket/

  2. $mvn clean install

  3. $mvn jetty:run

  4. Point your web browser (I used Google Chrome) to http://localhost:8080/index.html

java.lang.NullPointerException
    at org.eclipse.jetty.websocket.WebSocketFactory.upgrade(WebSocketFactory.java:236)[jetty-websocket-8.1.9.v20130131.jar:8.1.9.v20130131]
    at org.eclipse.jetty.websocket.WebSocketFactory.acceptWebSocket(WebSocketFactory.java:382)[jetty-websocket-8.1.9.v20130131.jar:8.1.9.v20130131]
    at org.eclipse.jetty.websocket.WebSocketServlet.service(WebSocketServlet.java:104)[jetty-websocket-7.6.8.v20121106.jar:7.6.8.v20121106]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)[javax.servlet-3.0.0.v201112011016.jar:]
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:598)[jetty-servlet-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:486)[jetty-servlet-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:413)[jetty-servlet-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:999)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.Server.handle(Server.java:350)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:454)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:890)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:944)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:630)[jetty-http-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:230)[jetty-http-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:77)[jetty-server-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:606)[jetty-io-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:46)[jetty-io-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:603)[jetty-util-8.1.3.v20120416.jar:8.1.9.v20130131]
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:538)[jetty-util-8.1.3.v20120416.jar:8.1.9.v20130131]
    at java.lang.Thread.run(Thread.java:680)[:1.6.0_45]

Here is my main Camel route. 

package demo.websocket; 

import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.twitter.TwitterComponent;
import org.apache.camel.component.websocket.WebsocketComponent;

public class TwitterStreamRoute extends RouteBuilder{

        //put your twitter keys here to test 
        public final String CONSUMER_KEY = ""; 
        public final String CONSUMER_SECRET = ""; 
        public final String ACCESS_TOKEN = ""; 
        public final String ACCESS_TOKEN_SECRET = ""; 


        @Override
        public void configure() throws Exception {




        TwitterComponent tc = getContext().getComponent("twitter", TwitterComponent.class);
        tc.setAccessToken(ACCESS_TOKEN);
        tc.setAccessTokenSecret(ACCESS_TOKEN_SECRET);
        tc.setConsumerKey(CONSUMER_KEY);
        tc.setConsumerSecret(CONSUMER_SECRET);

        fromF("twitter://streaming/filter?type=polling&delay=%s&keywords=%s", "5", "pittsburgh")
                .process(new Processor() {
                                @Override
                                public void process(Exchange exchange) throws Exception {
                                        String res = exchange.getIn().getBody().toString();
                                        exchange.getOut().setBody(res);
                                }   
                        })  
        .to("websocket://0.0.0.0:9292/camel-tweet?sendToAll=true");
        }   

}

The Camel config looks like the following: 

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:camel="http://camel.apache.org/schema/spring"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">


    <!-- Here we define Camel, notice the namespace it uses -->
    <camelContext xmlns="http://camel.apache.org/schema/spring" trace="true">
        <routeBuilder ref="twitter-route-id" ></routeBuilder>
    </camelContext>

    <bean id="twitter-route-id" class="demo.websocket.TwitterStreamRoute" />

</beans>

My web.xml looks like 

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://java.sun.com/xml/ns/javaee"
        xmlns:camel="http://camel.apache.org/schema/spring"
        xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
                xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
                        id="WebApp_ID" version="3.0">
                          <!-- your web.xml content here -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            classpath:camel-config.xml
        </param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <listener>
        <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
    </listener>


  <display-name>Archetype Created Web Application</display-name>
                          </web-app>

~

I'm using the following versions in my pom.xml. The full pom.xml is here. 

    <properties>
            <spring.version>3.2.2.RELEASE</spring.version>
            <camel.version>2.11.0</camel.version>
            <jetty.version>8.1.3.v20120416</jetty.version>
    </properties>

UPDATE (6-May-2013, 3:04 PM EST)

I updated the pom.xml to use Jetty 7.6.x release as suggested by Claus Ibsen. But I'm still getting the same error. Also in this case the stackstrace have the same version numbers for WebSocketFactory and WebSocketServlet. 

java.lang.NullPointerException
    at org.eclipse.jetty.websocket.WebSocketFactory.upgrade(WebSocketFactory.java:236)[jetty-websocket-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.websocket.WebSocketFactory.acceptWebSocket(WebSocketFactory.java:382)[jetty-websocket-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.websocket.WebSocketServlet.service(WebSocketServlet.java:104)[jetty-websocket-7.6.8.v20121106.jar:7.6.8.v20121106]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)[javax.servlet-2.5.0.v201103041518.jar:]
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:652)[jetty-servlet-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:447)[jetty-servlet-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1038)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:374)[jetty-servlet-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:972)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.Server.handle(Server.java:363)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:483)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:920)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:982)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:635)[jetty-http-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)[jetty-http-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)[jetty-server-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)[jetty-io-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)[jetty-io-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)[jetty-util-7.6.8.v20121106.jar:7.6.8.v20121106]
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)[jetty-util-7.6.8.v20121106.jar:7.6.8.v20121106]
    at java.lang.Thread.run(Thread.java:662)[:1.6.0_32]

UPDATE 2 (6-May-2013 4:06 PM EST) As suggested by @JoakimErdfelt in the comments the Google Chrome file with request response information is here.

4
websocketjettyapache-camel
Your stacktrace says Jetty 8.1.9.v20130131, but your pom says Jetty 8.1.3.v20120416. That is a bit confusing. - Joakim Erdfelt
Yeah that's strange. Let me debug it a little bit more. - Soumya Simanta
I updated the original question with a new stacktrace. - Soumya Simanta
Include which version of Google Chrome you used to cause this. Or better yet, capture your network traffic, HTTP request for upgrade (and HTTP response) and post it. (Look into the built-in Chrome network inspector or chrome://net-internals as techniques). - Joakim Erdfelt
@JoakimErdfelt - Thanks. I'll update the Google Chrome version. I get the same error on Google Chrome running on Windows/Linux/OS-X. I'm pretty sure if you clone the git repo you will also get the same error. I'll try get the HTTP request and response. - Soumya Simanta

4 Answers

3
votes

I don't think I've figured out the exact reason behind this error. However, I've a solution that works without major changes to the code.

I believe the problem is with the classloading for websocket related classes in Jetty and the Jetty-maven-plugin. Either my plugin in my pom.xml is not configured properly or I'm missing some entries. In any case, after trying this out for almost a day my alternative solution is as follows:

Instead of using the Jetty-maven-plugin to deploy the application I used Jetty Runner (http://wiki.eclipse.org/Jetty/Howto/Using_Jetty_Runner) to deploy the application. NOTE: Please download the version that is matches your jetty.version in your pom.xml.

For example: 

$java -jar jetty-runner-7.6.8.v20121106.jar target/jettycamelwebsocket.war

After this I was able to access the websocket from my index.html without any issues.

Now if someone could explain why this doesn't work (or what's missing) from the Jetty-maven-plugin it would be really useful.

Here are a few references that I found useful. Although they are dated some of them gave me a hint that there maybe something wrong with the Jetty Maven Plugin, therefore pointing me the correct direction.

http://dev.eclipse.org/mhonarc/lists/jetty-users/msg00263.html

2
votes

I faced the same exception couple of days back. The issue is null Connection object. At least for me the root cause was jetty settings. Make sure you have websocket enabled in your jetty start.ini file. Something like this -

OPTIONS=Server,jsp,resources,ext,plus,websocket

It should be enabled by default, but it wasn't in our case since somebody customized our start.ini and removed websocket support by mistake. After adding it back websocket worked like charm with Jetty 7.6.8.

1
votes

The NPE on WebSocketFactory:236 is due to an attempt to upgrade without arriving in via a real Jetty HTTP connection.

The most common causes for this:

  • Attempting to use Jetty WebSockets on a web container that isn't jetty. (such as tomcat or jboss)
  • Attempting to unit test your websocket (servlet) without using a real HTTP connection (such as via a mocking library)
0
votes

Try use Jetty 7.6.x as thats the version we test and used for the Apache Camel 2.11 release.