Fix parent state ref

- For RepositoryState, its parent state is now
  defined as RepositoryState as well allowing
  to reference from a json files.
- Relates to #262

spring-statemachine-data/jpa/src/main/java/org/springframework/statemachine/data/jpa/JpaRepositoryState.java

@@ -24,6 +24,7 @@ import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.OneToMany;
+import javax.persistence.OneToOne;
 
 import org.springframework.statemachine.data.RepositoryState;
 
@@ -45,10 +46,12 @@ public class JpaRepositoryState extends RepositoryState {
 	private long id;
 
 	private String machineId;
-	private String parentState;
 	private String state;
 	private boolean initial;
 
+	@OneToOne(fetch = FetchType.EAGER)
+	private JpaRepositoryState parentState;
+
 	@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
 	private Set<JpaRepositoryAction> stateActions;
 
@@ -102,7 +105,7 @@ public class JpaRepositoryState extends RepositoryState {
 	 * @param state the state
 	 * @param initial the initial
 	 */
-	public JpaRepositoryState(String machineId, String parentState, String state, boolean initial) {
+	public JpaRepositoryState(String machineId, JpaRepositoryState parentState, String state, boolean initial) {
 		this(machineId, parentState, state, initial, null, null, null);
 	}
 
@@ -117,7 +120,7 @@ public class JpaRepositoryState extends RepositoryState {
 	 * @param entryActions the entry actions
 	 * @param exitActions the exit actions
 	 */
-	public JpaRepositoryState(String machineId, String parentState, String state, boolean initial, Set<JpaRepositoryAction> stateActions,
+	public JpaRepositoryState(String machineId, JpaRepositoryState parentState, String state, boolean initial, Set<JpaRepositoryAction> stateActions,
 			Set<JpaRepositoryAction> entryActions, Set<JpaRepositoryAction> exitActions) {
 		this.machineId = machineId;
 		this.parentState = parentState;
@@ -138,11 +141,11 @@ public class JpaRepositoryState extends RepositoryState {
 	}
 
 	@Override
-	public String getParentState() {
+	public JpaRepositoryState getParentState() {
 		return parentState;
 	}
 
-	public void setParentState(String parentState) {
+	public void setParentState(JpaRepositoryState parentState) {
 		this.parentState = parentState;
 	}
 

spring-statemachine-data/jpa/src/test/resources/data3.json

@@ -15,14 +15,14 @@
 		"@id": "3",
 		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryState",
 		"initial": true,
-		"parentState": "S2",
+		"parentState": "2",
 		"state": "S20"
 	},
 	{
 		"@id": "4",
 		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryState",
 		"initial": false,
-		"parentState": "S2",
+		"parentState": "2",
 		"state": "S21"
 	},
 	{

spring-statemachine-data/src/main/java/org/springframework/statemachine/data/RepositoryState.java

@@ -30,7 +30,7 @@ public abstract class RepositoryState extends BaseRepositoryEntity {
 	 *
 	 * @return the parent state
 	 */
-	public abstract String getParentState();
+	public abstract RepositoryState getParentState();
 
 	/**
 	 * Gets the machine id.

spring-statemachine-data/src/main/java/org/springframework/statemachine/data/RepositoryStateMachineModelFactory.java

@@ -132,7 +132,9 @@ public class RepositoryStateMachineModelFactory extends AbstractStateMachineMode
 				}
 			}
 
-			StateData<String,String> stateData = new StateData<String, String>(s.getParentState(), null, s.getState(), s.isInitial());
+			RepositoryState parentState = s.getParentState();
+			StateData<String, String> stateData = new StateData<String, String>(parentState != null ? parentState.getState() : null, null,
+					s.getState(), s.isInitial());
 			stateData.setStateActions(stateActions);
 			stateData.setEntryActions(entryActions);
 			stateData.setExitActions(exitActions);