Initial config error model and spi

- Move into a generic fail fast configuration error
  model with better exception messages.
- Initial move into a public SPI for state machine
  configuration pojo classes.
- new StateMachineModelVerifier interface for generic model verifying.
- Relates #103
- Relates #172
- Work is done together for above issues mostly because they
  relate to each others for config error handling. Meaning
  we can't really verify configuration if we don't have
  a proper model describing actual config model.

spring-statemachine-core/src/test/java/org/springframework/statemachine/config/ConfigurationErrorTests.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.statemachine.config;
+
+import static org.hamcrest.Matchers.isA;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.statemachine.AbstractStateMachineTests;
+import org.springframework.statemachine.config.StateMachineBuilder.Builder;
+import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
+import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
+import org.springframework.statemachine.config.model.MalformedConfigurationException;
+
+public class ConfigurationErrorTests extends AbstractStateMachineTests {
+
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
+
+	@Override
+	protected AnnotationConfigApplicationContext buildContext() {
+		return new AnnotationConfigApplicationContext();
+	}
+
+	@Test
+	public void testFoo1() {
+		expectedException.expectCause(isA(MalformedConfigurationException.class));
+		context.register(Config1.class);
+		context.refresh();
+	}
+
+	@Test
+	public void testFoo2() throws Exception {
+		expectedException.expectCause(isA(MalformedConfigurationException.class));
+		Builder<String, String> builder = StateMachineBuilder.builder();
+		builder
+			.configureStates()
+				.withStates()
+					.state("S1")
+					.state("S2");
+		builder
+			.configureTransitions()
+				.withExternal()
+					.source("S1")
+					.target("S2")
+					.event("E1");
+
+		builder.build();
+	}
+
+	@Configuration
+	@EnableStateMachine
+	public static class Config1 extends StateMachineConfigurerAdapter<String, String> {
+		// initial state not set
+
+		@Override
+		public void configure(StateMachineStateConfigurer<String, String> states) throws Exception {
+			states
+				.withStates()
+					//.initial("S1")
+					.state("S1")
+					.state("S2");
+		}
+
+		@Override
+		public void configure(StateMachineTransitionConfigurer<String, String> transitions) throws Exception {
+			transitions
+				.withExternal()
+					.source("S1")
+					.target("S2")
+					.event("E1");
+		}
+	}
+
+}

spring-statemachine-core/src/test/java/org/springframework/statemachine/config/ManualBuilderTests.java

@@ -33,11 +33,11 @@ import org.springframework.statemachine.StateMachineSystemConstants;
 import org.springframework.statemachine.TestUtils;
 import org.springframework.statemachine.config.StateMachineBuilder.Builder;
 import org.springframework.statemachine.config.builders.StateMachineConfigBuilder;
-import org.springframework.statemachine.config.builders.StateMachineConfigurationConfig;
 import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
-import org.springframework.statemachine.config.builders.StateMachineStates;
 import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
-import org.springframework.statemachine.config.builders.StateMachineTransitions;
+import org.springframework.statemachine.config.model.StateMachineConfigurationConfig;
+import org.springframework.statemachine.config.model.StateMachineStates;
+import org.springframework.statemachine.config.model.StateMachineTransitions;
 import org.springframework.statemachine.listener.StateMachineListenerAdapter;
 import org.springframework.statemachine.state.State;
 

spring-statemachine-core/src/test/java/org/springframework/statemachine/config/configurers/DefaultStateConfigurerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,8 +29,8 @@ import org.springframework.statemachine.AbstractStateMachineTests.TestEvents;
 import org.springframework.statemachine.AbstractStateMachineTests.TestExitAction;
 import org.springframework.statemachine.AbstractStateMachineTests.TestStates;
 import org.springframework.statemachine.action.Action;
-import org.springframework.statemachine.config.StateData;
 import org.springframework.statemachine.config.builders.StateMachineStateBuilder;
+import org.springframework.statemachine.config.model.StateData;
 import org.springframework.statemachine.state.PseudoStateKind;
 
 public class DefaultStateConfigurerTests {