Better support for parallel regions

- Generally fixes #68
- First attempt to externalize event execution from state machine
  into its own class backed by an interface. This relates to #7
- Change of various places to have better support if execution
  is done in threads.
- Not yet a central place where concurrency can be defines, thus
  currently rely on global taskExecutor bean when can be overridded
  from a default which is SyncTaskExecutor. Futher work for
  that in separate tickets.
- Change tasks sample to use a thread pool.
- Change of concept how initial state/transition is handled, no
  longer handled manually in lifecycle method, thus giving a change
  for initial transition to execute its actions in a multiple threads.

spring-statemachine-samples/tasks/src/main/java/demo/tasks/Application.java

@@ -8,6 +8,8 @@ import java.util.Map;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.task.TaskExecutor;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 import org.springframework.shell.Bootstrap;
 import org.springframework.statemachine.StateContext;
 import org.springframework.statemachine.action.Action;
@@ -127,8 +129,7 @@ public class Application  {
 				@Override
 				public void execute(StateContext<States, Events> context) {
 					Map<Object, Object> variables = context.getExtendedState().getVariables();
-					if (variables.get("T1").equals(false)) {
-						variables.put("T1", true);
+					if (variables.get("T1").equals(true)) {
 						context.getStateMachine().sendEvent(Events.CONTINUE);
 					} else {
 						context.getStateMachine().sendEvent(Events.FALLBACK);
@@ -157,6 +158,13 @@ public class Application  {
 			return new Tasks();
 		}
 
+		@Bean
+		public TaskExecutor taskExecutor() {
+			ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
+			taskExecutor.setCorePoolSize(5);
+			return taskExecutor;
+		}
+
 	}
 //end::snippetA[]
 

spring-statemachine-samples/tasks/src/main/java/demo/tasks/Tasks.java

@@ -54,19 +54,25 @@ public class Tasks {
 	@StatesOnTransition(target = States.T1)
 	public void taskT1(ExtendedState extendedState) {
 		log.info("run task on T1");
+		sleep(2000);
 		extendedState.getVariables().put("T1", tasks.get("T1"));
+		log.info("run task on T1 done");
 	}
 
 	@StatesOnTransition(target = States.T2)
 	public void taskT2(ExtendedState extendedState) {
 		log.info("run task on T2");
+		sleep(2000);
 		extendedState.getVariables().put("T2", tasks.get("T2"));
+		log.info("run task on T2 done");
 	}
 
 	@StatesOnTransition(target = States.T3)
 	public void taskT3(ExtendedState extendedState) {
 		log.info("run task on T3");
+		sleep(2000);
 		extendedState.getVariables().put("T3", tasks.get("T3"));
+		log.info("run task on T3 done");
 	}
 
 	@StatesOnTransition(target = States.AUTOMATIC)
@@ -87,6 +93,13 @@ public class Tasks {
 		}
 	}
 
+	private static void sleep(long millis) {
+		try {
+			Thread.sleep(millis);
+		} catch (InterruptedException e) {
+		}
+	}
+
 	@Override
 	public String toString() {
 		return "Tasks " + tasks;

spring-statemachine-samples/tasks/src/test/java/demo/tasks/TasksTests.java

@@ -46,22 +46,22 @@ public class TasksTests {
 
 	@Test
 	public void testRunOnce() throws InterruptedException {
-		listener.reset(3, 0, 0);
+		listener.reset(9, 0, 0);
 		tasks.run();
-		assertThat(listener.stateChangedLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.stateChangedLatch.await(6, TimeUnit.SECONDS), is(true));
 		assertThat(machine.getState().getIds(), contains(States.READY));
 	}
 
 	@Test
 	public void testRunTwice() throws InterruptedException {
-		listener.reset(3, 0, 0);
+		listener.reset(9, 0, 0);
 		tasks.run();
-		assertThat(listener.stateChangedLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.stateChangedLatch.await(6, TimeUnit.SECONDS), is(true));
 		assertThat(machine.getState().getIds(), contains(States.READY));
 
-		listener.reset(3, 0, 0);
+		listener.reset(9, 0, 0);
 		tasks.run();
-		assertThat(listener.stateChangedLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.stateChangedLatch.await(6, TimeUnit.SECONDS), is(true));
 		assertThat(machine.getState().getIds(), contains(States.READY));
 	}
 
@@ -70,19 +70,19 @@ public class TasksTests {
 		listener.reset(11, 0, 0);
 		tasks.fail("T1");
 		tasks.run();
-		assertThat(listener.stateChangedLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.stateChangedLatch.await(6, TimeUnit.SECONDS), is(true));
 		assertThat(listener.stateChangedCount, is(11));
 		assertThat(machine.getState().getIds(), contains(States.READY));
 	}
 
 	@Test
 	public void testFailManualFix() throws InterruptedException {
-		listener.reset(3, 0, 0);
+		listener.reset(9, 0, 0);
 		tasks.fail("T2");
 		tasks.run();
 		tasks.fix("T2");
 		tasks.cont();
-		assertThat(listener.stateChangedLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.stateChangedLatch.await(6, TimeUnit.SECONDS), is(true));
 		assertThat(machine.getState().getIds(), contains(States.READY));
 	}