Having problems getting Email to work while following Google App Engine Tutorial for Java

Question

I've been working my way through a Google App Engine tutorial.

I entered the code shown in section 6 and then tried to test the functionality as instructed.

However, regardless of what email address I put in the form's To: field, I get an error that looks like this:

Message send failure
HTTP ERROR 404
Problem accessing /_ah/mail/someemail@gmail.com. Reason:
    NOT_FOUND
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Event though the test was apparently failing, I deployed the application to appspot.com

Here, I could not even access /_ah/mail/, so I sent an e-mail from Outlook. The application didn't receive it and the following bounced back:

Delivery to the following recipient failed permanently:

     whatever@fromsometutorial.applicationid.appspotmail.com

----- Original message -----

Received: by 10.204.82.130 with SMTP id b2mr13438bkl.0.1285692691837;
        Tue, 28 Sep 2010 09:51:31 -0700 (PDT)
Return-Path: <kessler.bm@gmail.com>
Received: from mail-bw0-f46.google.com (mail-bw0-f46.google.com
[209.85.214.46])
        by gmr-mx.google.com with ESMTP id z25si3874412bku.
5.2010.09.28.09.51.30;
        Tue, 28 Sep 2010 09:51:30 -0700 (PDT)
Received-SPF: pass (google.com: domain of kessler.bm@gmail.com designates 209.85.214.46 as permitted sender) client-ip=209.85.214.46;
Authentication-Results: gmr-mx.google.com; spf=pass (google.com:
domain of kessler.bm@gmail.com designates 209.85.214.46 as permitted
sender) smtp.mail=kessler.bm@gmail.com; dkim=pass (test mode) header.i=@gmail.com
Received: by bwz11 with SMTP id 11so5254251bwz.5
        for <whatever@fromsometutorial.applicationid.appspotmail.com>;
Tue, 28 Sep 2010 09:51:30 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=domainkey-signature:received:received:reply-
to:from:to:subject:date
         :organization:message-id:mime-version:content-type
         :content-transfer-encoding:x-mailer:thread-index:x-mimeole;
        bh=5hMmQ/fy4AdMWGj7dA7tHInFNumFfhg24xHggsIZKR4=;
        b=OitMOXiZONheUMpkDU8mVUdWhk2AhUAuBbnSnyqDs1WWOPx0Ao75bWHBZZ/
lhRtOO+
         yMvLhDvrN+/cTDnxuQI6ICBb1KZh9eeExMrgdaQGV+/
pnaBK3PAEotfL8QgX81V1AKFE
         j58cbhxWUH0JSTVckXucribInLNCNJnIqvyD0=
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=reply-to:from:to:subject:date:organization:message-id:mime-
version
         :content-type:content-transfer-encoding:x-mailer:thread-index
         :x-mimeole;

b=Adh4j5+8xWF7MKIT6YTBE8PXH2iQG4yi2hulXgQ0QL5ZB1qmTNJiu5U2MlwWzJF7zQ
         DR1uBnwVNu0WtZxzHbneVsZY
+aSH8sPrmgPFTZSHTGcCU0+SXW9UjyZndVJdFhPP2Nfc
         GBeolrTikuhBtU+1F9T23io6wJqEwLg7X6HnU=
Received: by 10.204.58.75 with SMTP id f11mr192120bkh.
138.1285692690387;
        Tue, 28 Sep 2010 09:51:30 -0700 (PDT)
Return-Path: <kessler.bm@gmail.com>
Received: from blackbox (catv-86-101-152-197.catv.broadband.hu
[86.101.152.197])
        by mx.google.com with ESMTPS id 11sm5779682bkj.
23.2010.09.28.09.51.27
        (version=TLSv1/SSLv3 cipher=RC4-MD5);
        Tue, 28 Sep 2010 09:51:29 -0700 (PDT)
Reply-To: <kessler.bm@gmail.com>
From: "Brian Kessler" <kessler.bm@gmail.com>
To: <whatever@fromsometutorial.applicationid.appspotmail.com>
Subject: Go south
Date: Tue, 28 Sep 2010 18:52:12 +0200
Organization: Flux Szerviz BT.
Message-ID: <A878B05D923A4EDEBC8015D3B5448D2F@blackbox>
MIME-Version: 1.0
Content-Type: text/plain;
    charset="us-ascii"
Content-Transfer-Encoding: 7bit
X-Mailer: Microsoft Office Outlook 11
thread-index: ActfLX7QaTtIrEoETYWtToubxBHBOw==
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994

Way down south to mexico

--
Brian Kessler
kessler.bm@gmail.com
+36 30 637 1824

Following a suggestion below, I modified the tutorial's

<servlet-mapping>
    <servlet-name>Email</servlet-name>
    <url-pattern>/_ah/mail/*</url-pattern>
</servlet-mapping>

to read:

<servlet-mapping>
    <servlet-name>Email</servlet-name>
    <url-pattern>/_ah/mail/.+</url-pattern>
</servlet-mapping>

which drastically changed the error when I tried to submit an email on the local server to:

Message send failure
HTTP ERROR 500
Problem accessing /_ah/mail/kessler.bm@gmail.com. Reason:
    de/vogella/gae/java/todo/dao/Dao
Caused by:
java.lang.NoClassDefFoundError: de/vogella/gae/java/todo/dao/Dao
    at de.vogella.gae.java.todo.EmailServlet.doPost(EmailServlet.java:43)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:58)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:349)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.lang.ClassNotFoundException: de.vogella.gae.java.todo.dao.Dao
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:151)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    ... 28 more
Caused by:
java.lang.ClassNotFoundException: de.vogella.gae.java.todo.dao.Dao
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:151)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    at de.vogella.gae.java.todo.EmailServlet.doPost(EmailServlet.java:43)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:58)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:349)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
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However, as per the tutorial, de.vogella.gae.java.todo.dao.Dao exists as an enum instead of a class. I tried to change this to a class, but eclipse immediately started to complain

Syntax Error on token "INSTANCE".  VariableDeclarator expected after this token.

Is the original tutorial doing so much wrong? And how can I fix it?

Answer 1

Your web.xml needs an entry that matches /_ah/mail/*, with a mapping to a servlet that handles those addresses.

Answer 2

Tutorial is missing this section in web.xml file

<security-constraint>
  <web-resource-collection>
    <url-pattern>/_ah/mail/*</url-pattern>
  </web-resource-collection>
  <auth-constraint>
    <role-name>admin</role-name>
  </auth-constraint>
</security-constraint>

check here

Answer 3

You said:

However, as per the tutorial, de.vogella.gae.java.todo.dao.Dao exists as an enum instead of a class. I tried to change this to a class, but eclipse immediately started to complain

Actually, enum in java is compiled into a classes. Here is an excerpt from Java Tutorials page on enums:

The enum declaration defines a class (called an enum type). The enum class body can include methods and other fields. The compiler automatically adds some special methods when it creates an enum. For example, they have a static values method that returns an array containing all of the values of the enum in the order they are declared.

The error you are seeing after converting enum to class is because the line INSTANCE; is trying to define an enum constant and you can do that only in an enum, not in a normal class.

The original ava.lang.NoClassDefFoundError just meant that the compiled (enum) class is missing at runtime. You need to check your war/WEB-INF/lib/classes to confirm that the compile Dao.class is present in de.vogella.gae.java.todo.dao package.

By the way, the author of this tutorial is using enum for implementing singleton pattern.

Answer 4

I had a similar problem (using Python, so yaml config files rather than XML) and the cause turned out to be because I put the:

- url: /_ah/mail/.+ 
  script: handle_incoming_email.py 
  login: admin

before an existing catch-all entry:

- url: /.*
  script: main.py

This gave 404s on the server and "Message send failure" when sending test messages.

Moving it after the catch-all entry solved the problem.