different versions of defining a state machine

src/TODO.md

@@ -0,0 +1,52 @@
+1. extract state machines from this as well
+
+```java
+
+import org.springframework.statemachine.StateMachine;
+import org.springframework.statemachine.config.builders.StateMachineBuilder;
+
+import java.util.EnumSet;
+
+public class DynamicStateMachineExample {
+
+    public enum States {
+        DRAFT, REVIEW, APPROVED
+    }
+
+    public enum Events {
+        SUBMIT, APPROVE
+    }
+
+    public static StateMachine<States, Events> buildStateMachine() throws Exception {
+        StateMachineBuilder.Builder<States, Events> builder = StateMachineBuilder.builder();
+
+        builder.configureStates()
+            .withStates()
+                .initial(States.DRAFT)
+                .states(EnumSet.allOf(States.class));
+
+        builder.configureTransitions()
+            .withExternal()
+                .source(States.DRAFT).target(States.REVIEW).event(Events.SUBMIT)
+            .and()
+            .withExternal()
+                .source(States.REVIEW).target(States.APPROVED).event(Events.APPROVE);
+
+        return builder.build();
+    }
+
+    public static void main(String[] args) throws Exception {
+        StateMachine<States, Events> sm = buildStateMachine();
+
+        sm.start();
+        System.out.println("Current State: " + sm.getState().getId());
+
+        sm.sendEvent(Events.SUBMIT);
+        System.out.println("After SUBMIT: " + sm.getState().getId());
+
+        sm.sendEvent(Events.APPROVE);
+        System.out.println("After APPROVE: " + sm.getState().getId());
+    }
+}
+
+```