Update docs

- Add missing docs for @StatesOnTransition supported
  method arguments.
- Fixes #124

docs/src/reference/asciidoc/sm.adoc

@@ -679,6 +679,15 @@ Default _@OnTransition_ annotation can't be used with a state and
 event enums user have created due to java language limitations, thus
 string representation have to be used.
 
+Additionally it is possible to access `Event Headers` and
+`ExtendedState` by adding needed arguments to a method. Method
+is then called automatically with these arguments.
+
+[source,java,indent=0]
+----
+include::samples/DocsConfigurationSampleTests.java[tags=snippetII]
+----
+
 However if you want to have a type safe annotation it is possible to
 create a new annotation and use _@OnTransition_ as meta annotation.
 This user level annotation can make a reference to actual states and

spring-statemachine-core/src/test/java/org/springframework/statemachine/docs/DocsConfigurationSampleTests.java

@@ -22,6 +22,7 @@ import java.lang.annotation.Target;
 import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.HashSet;
+import java.util.Map;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.support.StaticListableBeanFactory;
@@ -36,12 +37,14 @@ import org.springframework.messaging.Message;
 import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.scheduling.concurrent.ConcurrentTaskScheduler;
 import org.springframework.statemachine.AbstractStateMachineTests;
+import org.springframework.statemachine.ExtendedState;
 import org.springframework.statemachine.StateContext;
 import org.springframework.statemachine.StateMachine;
 import org.springframework.statemachine.access.StateMachineAccess;
 import org.springframework.statemachine.access.StateMachineFunction;
 import org.springframework.statemachine.action.Action;
 import org.springframework.statemachine.action.SpelExpressionAction;
+import org.springframework.statemachine.annotation.EventHeaders;
 import org.springframework.statemachine.annotation.OnTransition;
 import org.springframework.statemachine.annotation.WithStateMachine;
 import org.springframework.statemachine.config.EnableStateMachine;
@@ -415,6 +418,16 @@ public class DocsConfigurationSampleTests extends AbstractStateMachineTests {
 	}
 // end::snippetI[]
 
+// tag::snippetII[]
+	@WithStateMachine
+	static class Bean4 {
+
+		@StatesOnTransition(source = States.S1, target = States.S2)
+		public void fromS1ToS2(@EventHeaders Map<String, Object> headers, ExtendedState extendedState) {
+		}
+	}
+// end::snippetII[]
+
 // tag::snippetJ[]
 	@Target(ElementType.METHOD)
 	@Retention(RetentionPolicy.RUNTIME)