When running gradle task `appengineRun`, my current spring boot projects boots up (*two times!?*) but can't be accessed via localhost (`jetty`):

```
15:46:39: Executing task 'appengineRun'...

> Task :compileJava
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

> Task :processResources
> Task :classes
> Task :bootWar
> Task :war SKIPPED
> Task :explodeWar
> Task :assemble
Jun 03, 2018 3:46:51 PM com.google.appengine.tools.development.SystemPropertiesManager setSystemProperties
INFORMATION: Overwriting system property key 'java.util.logging.config.file', value '/Users/sullrich/Downloads/google-cloud-sdk/platform/google_appengine/google/appengine/tools/java/config/sdk/logging.properties' with value 'WEB-INF/logging.properties' from '/Users/sullrich/github/WettkampfDB/build/exploded-WettkampfDB/WEB-INF/appengine-web.xml'
2018-06-03 15:46:52.110:INFO::main: Logging initialized @590ms
2018-06-03 15:46:52.452:INFO:oejs.Server:main: jetty-9.3.18.v20170406
2018-06-03 15:46:53.939:WARN:oeja.ClassInheritanceHandler:qtp710714889-15: 
java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936)
    at org.eclipse.jetty.annotations.ClassInheritanceHandler.addToInheritanceMap(ClassInheritanceHandler.java:72)
    at org.eclipse.jetty.annotations.ClassInheritanceHandler.handle(ClassInheritanceHandler.java:58)
    at org.eclipse.jetty.annotations.AnnotationParser$MyClassVisitor.visit(AnnotationParser.java:476)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:650)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:525)
    at org.eclipse.jetty.annotations.AnnotationParser.scanClass(AnnotationParser.java:978)
    at org.eclipse.jetty.annotations.AnnotationParser.parseJarEntry(AnnotationParser.java:958)
    at org.eclipse.jetty.annotations.AnnotationParser.parseJar(AnnotationParser.java:902)
    at org.eclipse.jetty.annotations.AnnotationParser.parse(AnnotationParser.java:851)
    at org.eclipse.jetty.annotations.AnnotationConfiguration$ParserTask.call(AnnotationConfiguration.java:163)
    at org.eclipse.jetty.annotations.AnnotationConfiguration$1.run(AnnotationConfiguration.java:546)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589)
    at java.lang.Thread.run(Thread.java:745)
2018-06-03 15:46:55.196:INFO:oeja.AnnotationConfiguration:main: Scanning elapsed time=2357ms
Jun 03, 2018 1:46:56 PM com.google.appengine.tools.development.ApiProxyLocalImpl log
INFORMATION: javax.servlet.ServletContext log: 2 Spring WebApplicationInitializers detected on classpath
13:46:56 INFO  [de.deepsource.container.ServletInitializer] : Starting WettkampfDB via SpringBootServletInitializer

[project boot logs; then second start ...]

13:47:10 INFO  [de.deepsource.container.ServletInitializer] : Started ServletInitializer in 13.613 seconds (JVM running for 18.539)
Jun 03, 2018 1:47:10 PM com.google.appengine.tools.development.ApiProxyLocalImpl log
INFORMATION: javax.servlet.ServletContext log: Initializing Spring FrameworkServlet 'dispatcherServlet'
13:47:10 INFO  [org.springframework.web.servlet.DispatcherServlet] : FrameworkServlet 'dispatcherServlet': initialization started
13:47:10 INFO  [org.springframework.web.servlet.DispatcherServlet] : FrameworkServlet 'dispatcherServlet': initialization completed in 12 ms
2018-06-03 15:47:10.294:INFO:oejsh.ContextHandler:main: Started c.g.a.t.d.j.DevAppEngineWebAppContext@6318ff9{/,file:///Users/sullrich/github/WettkampfDB/build/exploded-WettkampfDB/,AVAILABLE}{/Users/sullrich/github/WettkampfDB/build/exploded-WettkampfDB}
2018-06-03 15:47:10.304:INFO:oejs.AbstractConnector:main: Started NetworkTrafficSelectChannelConnector@3f2d2f22{HTTP/1.1,[http/1.1]}{localhost:4000}
2018-06-03 15:47:10.310:INFO:oejs.Server:main: Started @18790ms
Jun 03, 2018 1:47:10 PM com.google.appengine.tools.development.AbstractModule startup
INFORMATION: Module instance default is running at http://localhost:4000/
Jun 03, 2018 1:47:10 PM com.google.appengine.tools.development.AbstractModule startup
INFORMATION: The admin console is running at http://localhost:4000/_ah/admin
2018-06-03 15:47:10.371:INFO:oejs.Server:main: jetty-9.3.18.v20170406
2018-06-03 15:47:10.836:WARN:oeja.ClassInheritanceHandler:qtp827966648-38: 
java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936)
    at org.eclipse.jetty.annotations.ClassInheritanceHandler.addToInheritanceMap(ClassInheritanceHandler.java:72)
    at org.eclipse.jetty.annotations.ClassInheritanceHandler.handle(ClassInheritanceHandler.java:58)
    at org.eclipse.jetty.annotations.AnnotationParser$MyClassVisitor.visit(AnnotationParser.java:476)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:650)
    at org.objectweb.asm.ClassReader.accept(ClassReader.java:525)
    at org.eclipse.jetty.annotations.AnnotationParser.scanClass(AnnotationParser.java:978)
    at org.eclipse.jetty.annotations.AnnotationParser.parseJarEntry(AnnotationParser.java:958)
    at org.eclipse.jetty.annotations.AnnotationParser.parseJar(AnnotationParser.java:902)
    at org.eclipse.jetty.annotations.AnnotationParser.parse(AnnotationParser.java:851)
    at org.eclipse.jetty.annotations.AnnotationConfiguration$ParserTask.call(AnnotationConfiguration.java:163)
    at org.eclipse.jetty.annotations.AnnotationConfiguration$1.run(AnnotationConfiguration.java:546)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589)
    at java.lang.Thread.run(Thread.java:745)
2018-06-03 15:47:11.798:INFO:oeja.AnnotationConfiguration:main: Scanning elapsed time=1343ms
Jun 03, 2018 1:47:12 PM com.google.appengine.tools.development.ApiProxyLocalImpl log
INFORMATION: javax.servlet.ServletContext log: 2 Spring WebApplicationInitializers detected on classpath
13:47:12 INFO  [de.deepsource.container.ServletInitializer] : Starting WettkampfDB via SpringBootServletInitializer

```

I haven't figure out why two `WebApplicationInitializers` are in my classpath: 

```
INFORMATION: javax.servlet.ServletContext log: 2 Spring WebApplicationInitializers detected on classpath

```

My `Server.class`:

```
@Log4j2
@SpringBootApplication

@EnableAsync
@EnableWebMvc
@EnableCaching
@EnableWebSecurity
@EnableHypermediaSupport(type = {EnableHypermediaSupport.HypermediaType.HAL})
@EnableAutoConfiguration

@ComponentScan("de.deepsource")
@EntityScan("de.deepsource")
@EnableJpaRepositories("de.deepsource")

@EnableGlobalMethodSecurity(prePostEnabled = true)
public class Server
{
    public static void main (String[] args)
    {
        log.info("Starting WettkampfDB via MainClass");
        SpringApplication.run(Server.class, args);
    }
}

```

My `ServletInitializer.class`:

```
@Log4j2
public class ServletInitializer extends SpringBootServletInitializer
{
    @Override
    protected SpringApplicationBuilder configure (SpringApplicationBuilder application)
    {
        log.info("Starting WettkampfDB via SpringBootServletInitializer");
        log.debug(application);
        return application.sources(Server.class);
    }
}

```

When accessing localhost:4000 I get Http-Status 500 saying: "all instances of module default are busy"

Update 1
========

I moved the war to a standalone jetty location. It still logs that `2 Spring WebApplicationInitializers detected on classpath` but jetty only boots up one instance that works perfectly on [localhost:8080/servlet-name](http://localhost:8080/servlet-name)

Update 2
========

My `build.gradle`

```
buildscript {
    ext {
        springBootVersion = '2.0.2.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
        classpath 'com.google.cloud.tools:appengine-gradle-plugin:+'
    }
}

apply plugin: 'java'
apply plugin: 'war'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
apply plugin: "com.google.cloud.tools.appengine"

appengine {
    run {
        port = 4000
    }
    deploy {
        stopPreviousVersion = true
        promote = true
    }
}

group 'de.deepsource'
sourceCompatibility = 1.8
targetCompatibility = 1.8

configurations {
    // Exclude default tomcat server
    compile.exclude module: "spring-boot-starter-tomcat"
    runtime.exclude module: 'spring-boot-starter-tomcat'

    // Exclude default spring logging (replaced with Log4j2)
    compile.exclude module: "spring-boot-starter-logging"
    compile.exclude group: "org.slf4j", module: "jul-to-slf4j"
}

repositories {
    mavenCentral()
    maven { url "http://repo.spring.io/milestone/" }
}

bootWar {
    mainClassName = 'de.deepsource.container.Server'
}

dependencies {
    // Spring Boot
    compile('org.springframework.boot:spring-boot-starter')
    compile('org.springframework.boot:spring-boot-starter-web')
    compile('org.springframework.boot:spring-boot-starter-data-jpa')
    compile('org.springframework.boot:spring-boot-starter-data-rest')
    compile('org.springframework.boot:spring-boot-starter-security')
    compile('org.springframework.boot:spring-boot-starter-mail')
    compile('org.springframework.boot:spring-boot-configuration-processor')
    compile("org.springframework.boot:spring-boot-starter-log4j2")
    runtime("org.springframework.boot:spring-boot-devtools")

    // Google App Engine Dependencies
    compile group: 'org.springframework.cloud', name: 'spring-cloud-gcp-starters', version: '1.0.0.M3'
    compile group: 'javax.servlet', name: 'javax.servlet-api'

    // Runtime provided Servlet Container
    // (THIS MUST BE EXCLUDED FOR GOOGLE APP ENGINE DEPLOYS)
    //compile('org.springframework.boot:spring-boot-starter-undertow')

    // Logger
    compile group: 'org.apache.logging.log4j', name: 'log4j-web', version: '2.7'

    // Thymeleaf HTML render engine
    compile("org.springframework.boot:spring-boot-starter-thymeleaf")
    compile("org.thymeleaf.extras:thymeleaf-extras-springsecurity4")

    // Model Mapper
    compile('org.modelmapper:modelmapper:1.1.1')
    compile('org.modelmapper.extensions:modelmapper-spring:1.1.1')

    // MapBox Service
    compile 'com.mapbox.mapboxsdk:mapbox-java-services:2.1.3'

    // OK HTTP client
    compile group: 'com.squareup.okhttp3', name: 'okhttp', version: '3.8.1'

    // MySQL connector
    runtime 'mysql:mysql-connector-java:6.0.5'

    // MailJet Client
    compile group: 'com.mailjet', name: 'mailjet-client', version: '4.1.1'

    // Google Cloud Stuff
    runtime 'com.google.cloud.sql:mysql-socket-factory-connector-j-6:1.0.3'
    compile 'com.google.apis:google-api-services-monitoring:v3-rev412-1.22.0'

    // Google utility library
    compile 'com.google.guava:guava:20.0'

    // Reduces java boilerplate code
    compile "org.projectlombok:lombok:1.16.10"

    // Reduces java boilerplate code
    compile 'org.apache.commons:commons-lang3:3.7'

    // Benchmarking
    compile group: 'com.googlecode.log4jdbc', name: 'log4jdbc', version: '1.2'

    // JUnit testing framework
    testCompile("org.springframework.security:spring-security-test")
    testCompile("org.springframework.boot:spring-boot-test")
    testCompile("org.springframework.boot:spring-boot-starter-test")
    testCompile("org.springframework.boot:spring-boot-test-autoconfigure")

    testCompile 'com.google.truth:truth:0.33'
    testCompile 'com.google.appengine:appengine-testing:+'
    testCompile 'com.google.appengine:appengine-api-stubs:+'
    testCompile 'com.google.appengine:appengine-tools-sdk:+'

    // JSoup
    testCompile group: 'org.jsoup', name: 'jsoup', version: '1.11.3'
    testCompile group: 'com.h2database', name: 'h2', version: '1.4.191'
}

```

Any ideas on how to fix this?