[SOLVED] Bare bones GAE app with Objectify fails

I used Eclipse IDE for Java Developers 4.7.3 to create a bare bones Google App Engine Standard application with Objectify. When I deploy the application and invoke the web service, I get java.lang.NoClassDefFoundError: Could not initialize class com.googlecode.objectify.ObjectifyService. What am I doing wrong? Here are the steps to reproduce this error:

Run Eclipse
From the Google Cloud Platform menu, choose Google App Engine Standard Standard Java Project
In the project name box, type a project name (e.g. ObjectifyTest)
In the Java version box, choose Java 8, Servlet 3.1
Check the create as Maven project box
In the group ID box, enter a group ID (e.g. com.pushpin.objectifytest)
In the artifact ID box, enter an artifact ID (e.g. objectifytest)
Check the Google Cloud Endpoints box
Check the Objectify box
Click finish
Open the web.xml file and add the ObjectifyFilter from https://github.com/objectify/objectify/wiki/Setup
From the Google Cloud Platform menu, choose Deploy to App Engine Standard
Click a project (or create a new one and then refresh)
Click deploy
Invoke the servlet (e.g. by opening https://pushpin-objectify-test.appspot.com/hello)
Note the 500 server error
Check the log
Note the java.lang.NoClassDefFoundError: Could not initialize class com.googlecode.objectify.ObjectifyService

Here is my web.xml:

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    version="3.1">
    <filter>
        <filter-name>ObjectifyFilter</filter-name>
        <filter-class>com.googlecode.objectify.ObjectifyFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>ObjectifyFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

Here is my pom.xml:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <packaging>war</packaging>
  <version>0.1.0-SNAPSHOT</version>

  <groupId>com.pushpin.objectifytest</groupId>
  <artifactId>objectifytest</artifactId>

  <properties>
    <appengine.maven.plugin.version>1.3.1</appengine.maven.plugin.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.showDeprecation>true</maven.compiler.showDeprecation>
  </properties>

  <prerequisites>
    <maven>3.3.9</maven>
  </prerequisites>

  <dependencies>
    <!-- Compile/runtime dependencies -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.3.1</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>com.google.appengine</groupId>
      <artifactId>appengine-api-1.0-sdk</artifactId>
      <version>1.9.57</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>

    <!-- Test Dependencies -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.google.endpoints</groupId>
      <artifactId>endpoints-framework</artifactId>
      <version>2.0.13</version>
    </dependency>
    <dependency>
      <groupId>com.googlecode.objectify</groupId>
      <artifactId>objectify</artifactId>
      <version>5.1.22</version>
    </dependency>
  </dependencies>

  <build>
    <!-- for hot reload of the web application-->
    <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
    <plugins>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>versions-maven-plugin</artifactId>
        <version>2.3</version>
        <executions>
          <execution>
            <phase>compile</phase>
            <goals>
              <goal>display-dependency-updates</goal>
              <goal>display-plugin-updates</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

      <plugin>
        <groupId>com.google.cloud.tools</groupId>
        <artifactId>appengine-maven-plugin</artifactId>
        <version>${appengine.maven.plugin.version}</version>
      </plugin>
    </plugins>
  </build>
</project>

Here is my HelloAppEngine.java file:

package com.pushpin.objectifytest;

import java.io.IOException;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(
    name = "HelloAppEngine",
    urlPatterns = {"/hello"}
)
public class HelloAppEngine extends HttpServlet {

  @Override
  public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws IOException {

    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");

    response.getWriter().print("Hello App Engine! 1a");

  }
}

Here is the stack trace:

com.google.apphosting.runtime.jetty9.JettyLogger warn: Error for /hello (JettyLogger.java:29)
java.lang.NoClassDefFoundError: Could not initialize class com.googlecode.objectify.ObjectifyService
    at com.googlecode.objectify.ObjectifyFilter.doFilter(ObjectifyFilter.java:47)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
    at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:125)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
    at com.google.apphosting.runtime.jetty9.SaveSessionFilter.doFilter(SaveSessionFilter.java:37)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
    at com.google.apphosting.utils.servlet.JdbcMySqlConnectionCleanupFilter.doFilter(JdbcMySqlConnectionCleanupFilter.java:60)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:48)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:582)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:512)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at com.google.apphosting.runtime.jetty9.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:297)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
    at org.eclipse.jetty.server.Server.handle(Server.java:534)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:320)
    at com.google.apphosting.runtime.jetty9.RpcConnection.handle(RpcConnection.java:202)
    at com.google.apphosting.runtime.jetty9.RpcConnector.serviceRequest(RpcConnector.java:81)
    at com.google.apphosting.runtime.jetty9.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:108)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.dispatchServletRequest(JavaRuntime.java:680)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.dispatchRequest(JavaRuntime.java:642)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:612)
    at com.google.apphosting.runtime.JavaRuntime$NullSandboxRequestRunnable.run(JavaRuntime.java:806)
    at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:274)
    at java.lang.Thread.run(Thread.java:745)