spring-boot on gretty fails on startup

I am trying to make a web-service using spring-boot. It works well when calling appStart in gradle, but it would show error when calling appStartWar.

This is the error:

Exception in thread "main" java.lang.ClassNotFoundException: com.example.server.Application
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:270)
    at java_lang_Class$forName.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:124)
    at org.akhikhl.gretty.SpringBootServerManager.startServer(SpringBootServerManager.groovy:46)
    at org.akhikhl.gretty.ServerManager$startServer$0.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at org.akhikhl.gretty.Runner.run(Runner.groovy:70)
    at org.akhikhl.gretty.Runner.this$2$run(Runner.groovy)
    at org.akhikhl.gretty.Runner$this$2$run.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
    at org.akhikhl.gretty.Runner.main(Runner.groovy:48)
Exception in thread "Thread-18" org.gradle.process.internal.ExecException: Process 'command 'C:\Program Files\Java\jdk1.7.0_51\bin\java.exe'' finished with non-zero exit value 1
    at org.gradle.process.internal.DefaultExecHandle$ExecResultImpl.assertNormalExitValue(DefaultExecHandle.java:365)
    at org.gradle.process.internal.DefaultJavaExecAction.execute(DefaultJavaExecAction.java:31)
    at org.gradle.api.internal.file.DefaultFileOperations.javaexec(DefaultFileOperations.java:159)
    at org.gradle.api.internal.project.AbstractProject.javaexec(AbstractProject.java:793)
    at org.gradle.api.Project$javaexec$8.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at org.akhikhl.gretty.DefaultLauncher.javaExec(DefaultLauncher.groovy:48)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
    at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:368)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1016)
    at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:66)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
    at org.akhikhl.gretty.LauncherBase$_launchThread_closure6.doCall(LauncherBase.groovy:216)
    at org.akhikhl.gretty.LauncherBase$_launchThread_closure6.doCall(LauncherBase.groovy)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
    at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:278)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1016)
    at groovy.lang.Closure.call(Closure.java:423)
    at groovy.lang.Closure.call(Closure.java:417)
    at groovy.lang.Closure.run(Closure.java:504)
    at java.lang.Thread.run(Thread.java:744)

It seems that it could not find the main class in war file, but the com.example.server.Application really exists in war with path WEB-INF/classes/com/example/server

build.gradle

apply plugin: 'java'
apply plugin: 'war'
apply plugin: 'spring-boot'
apply plugin: 'org.akhikhl.gretty'

buildscript {
    repositories {
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath 'org.akhikhl.gretty:gretty:1.1.8'
        classpath 'org.springframework.boot:spring-boot-gradle-plugin:1.2.2.RELEASE'
    }
}

dependencies{

    compile 'org.springframework.boot:spring-boot-starter-web:1.2.2.RELEASE'

    providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
    providedCompile 'javax.servlet:javax.servlet-api:3.1.0'

}

gretty {
    springBoot = true
    springBootVersion = '1.2.2.RELEASE'
    httpsEnabled = true
}

Application.java

@RestController
@SpringBootApplication
class Application extends SpringBootServletInitializer {

    public static void main( String[] args ) {
        SpringApplication.run( Application.class, args );
    }

    @Override
    protected SpringApplicationBuilder configure( SpringApplicationBuilder builder ) {
        return builder.sources( Application.class );
    }

    @RequestMapping( value = "test", method = RequestMethod.GET )
    public String test() {
        return "success";
    }


}

Any help appreciated :)

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Here's my project in Gitlab link