Starting a DMN Engine in a Bean does not work - camunda

Question

I will build a DMN Engine in a Bean. DMN Engine with a BPMN Business Rule Task works fine, but not the standalone way. Camunda 7.6 runs into a JBoss-EAP 7(Same WildFly Distribution) and I think the modules are on the right places. But the following code throws an error message.
DmnEngine dmnEngine = DmnEngineConfiguration.createDefaultDmnEngineConfiguration().buildEngine();
DecisionService is not enough for me because I want to read the inputs from DecisionLogic.
Caused by: java.lang.NoClassDefFoundError: javax/el/ELContext
at org.camunda.bpm.dmn.engine.impl.DefaultDmnEngineConfiguration.initElProvider(DefaultDmnEngineConfiguration.java:128)
at org.camunda.bpm.dmn.engine.impl.DefaultDmnEngineConfiguration.init(DefaultDmnEngineConfiguration.java:78)
at org.camunda.bpm.dmn.engine.impl.DefaultDmnEngineConfiguration.buildEngine(DefaultDmnEngineConfiguration.java:69)
at // DmnEngineConfiguration.createDefaultDmnEngineConfiguration().buildEngine();
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.jboss.as.ee.component.ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptor.java:52)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:437)
at org.jboss.as.weld.ejb.Jsr299BindingsInterceptor.doMethodInterception(Jsr299BindingsInterceptor.java:82)
at org.jboss.as.weld.ejb.Jsr299BindingsInterceptor.processInvocation(Jsr299BindingsInterceptor.java:93)
at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:63)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.as.ejb3.component.invocationmetrics.ExecutionTimeInterceptor.processInvocation(ExecutionTimeInterceptor.java:43)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.as.jpa.interceptor.SBInvocationInterceptor.processInvocation(SBInvocationInterceptor.java:47)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:437)
at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:64)
at org.jboss.as.weld.ejb.EjbRequestScopeActivationInterceptor.processInvocation(EjbRequestScopeActivationInterceptor.java:83)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.as.ee.concurrent.ConcurrentContextInterceptor.processInvocation(ConcurrentContextInterceptor.java:45)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.invocation.InitialInterceptor.processInvocation(InitialInterceptor.java:21)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61)
at org.jboss.as.ee.component.interceptors.ComponentDispatcherInterceptor.processInvocation(ComponentDispatcherInterceptor.java:52)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.as.ejb3.component.pool.PooledInstanceInterceptor.processInvocation(PooledInstanceInterceptor.java:51)
at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInCallerTx(CMTTxInterceptor.java:254)
... 324 more
Caused by: java.lang.ClassNotFoundException: javax.el.ELContext from [Module "org.camunda.bpm.dmn.camunda-engine-dmn:main" from local module loader #66133adc (finder: local module finder #7bfcd12c (roots: [JBOSS_HOME]\modules, [JBOSS_HOME]\modules\system\layers\base))]
at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:198)
at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:363)
at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:351)
at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:93)
... 357 more
The modul org.camunda.bpm.dmn.camunda-engine-dmn:main is there
Maven Dependencies
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.camunda.bpm</groupId>
<artifactId>camunda-bom</artifactId>
<version>${camunda.version}</version>
<scope>import</scope>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.camunda.bpm.dmn</groupId>
<artifactId>camunda-engine-dmn-bom</artifactId>
<version>${camunda.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
...
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.camunda.bpm</groupId>
<artifactId>camunda-engine</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.camunda.bpm.dmn</groupId>
<artifactId>camunda-engine-dmn</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.camunda.bpm.javaee</groupId>
<artifactId>camunda-ejb-client</artifactId>
</dependency>
<dependency>
<groupId>org.camunda.bpm</groupId>
<artifactId>camunda-engine-cdi</artifactId>
</dependency>
...
<dependencies>

Answer 1

you need to provide an implementation for the ELContext.
Add
<dependency>
<groupId>de.odysseus.juel</groupId>
<artifactId>juel</artifactId>
<version>2.1.3</version>
</dependency>
to your dependencies.

Answer 2

I use a workaround/hack to get the DMNEngine from the processEngine.
ProcessEngineConfiguration processEngineConfiguration = processEngine.getProcessEngineConfiguration();
Method method;
DmnEngine dmnEngine;
try {
method = ProcessEngineConfigurationImpl.class.getMethod("getDmnEngine");
dmnEngine = (DmnEngine) method.invoke(processEngineConfiguration);
} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException
| SecurityException e) {
e.printStackTrace();
}