"HTTP ERROR: 500 No realm" running GWT's "MobileWebApp" sample

Question

I'm trying to run the GWT 2.4 sample app "MobileWebApp". I get a 500 "No Realm" error when I try to run the app in dev mode through Eclipse.

I understand this is an authentication problem.

I'm not familiar with Google App Engine or Jetty but from looking at the web.xml I can see there is a servlet filter where it is using the appengine UserService to presumably redirect the user to Google for authentication.

I'm using:

• Eclipse 3.7 (Indigo SR1)
• Google Plugin for Eclipse 2.4
• m2eclipse

I'm including an excerpt from the web.xml below. I'm not sure what other info would be helpful in diagnosing this problem.

  <security-constraint>
    <display-name>
      Redirect to the login page if needed before showing
      the host html page.
    </display-name>
    <web-resource-collection>
      <web-resource-name>Login required</web-resource-name>
      <url-pattern>/MobileWebApp.html</url-pattern>
    </web-resource-collection>
    <auth-constraint>
      <role-name>*</role-name>
    </auth-constraint>
  </security-constraint>

  <filter>
    <filter-name>GaeAuthFilter</filter-name>
    <!--
      This filter demonstrates making GAE authentication
      services visible to a RequestFactory client.
    -->
    <filter-class>com.google.gwt.sample.gaerequest.server.GaeAuthFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>GaeAuthFilter</filter-name>
    <url-pattern>/gwtRequest/*</url-pattern>
  </filter-mapping>

Below is the output in the Eclipse console:

[WARN] Request /MobileWebApp.html failed - no realm
[ERROR] 500 - GET /MobileWebApp.html?gwt.codesvr=127.0.0.1:9997 (127.0.0.1) 1401 bytes
   Request headers
      Host: 127.0.0.1:8888
      User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:7.0.1) Gecko/20100101 Firefox/7.0.1
      Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
      Accept-Language: en-us,en;q=0.5
      Accept-Encoding: gzip, deflate
      Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
      Connection: keep-alive
   Response headers
      Content-Type: text/html; charset=iso-8859-1
      Content-Length: 1401

Many thanks for any helpful advice!

Edit on 11/11/11: I added Jetty tag since it seems relevant to this problem.

Answer 1

If your very first request fails, just getting the /MobileWebApp.html page, then it probably isn't an authentication problem. Do you have GAE enabled for that project (not only GWT)? That might be one issue.

I read somewhere that there's two ways of debugging an app in Eclipse, one is with run as/webapp, and forgot which was the other one (I don't use Eclipse). One of them works and another doesn't.

If that doesn't work, you can try replacing the built-in jetty:

• add a GWT param: -server com.google.appengine.tools.development.gwt.AppEngineLauncher
• VM param: -javaagent:/path_to/appengine-agent.jar

And the last option is with -noserver, but then you wont be able to debug the server-side code, just the client-side GWT stuff: first start jetty with mvn jetty:run and then debug in Eclipse with -noserver GWT param.