Improved code

src/main/java/org/gcube/informationsystem/resourceregistry/api/contexts/ContextCache.java

@@ -62,9 +62,12 @@ public class ContextCache {
 	protected Map<String, UUID> contextFullNameToUUID;
 	protected Tree<Context> contextsTree;
 	
+	protected boolean initialized;
+	
 	public ContextCache() {
 		Calendar now = Calendar.getInstance();
 		cleanCache(now);
+		initialized = false;
 	}
 	
 	public void cleanCache() {
@@ -72,7 +75,7 @@ public class ContextCache {
 	}
 	
 	protected void cleanCache(Calendar calendar) {
-		this.contexts = null;
+		this.contexts = new ArrayList<>();
 		this.uuidToContext = new LinkedHashMap<>();
 		this.uuidToContextFullName = new LinkedHashMap<>();
 		this.contextFullNameToUUID = new TreeMap<>();
@@ -84,6 +87,7 @@ public class ContextCache {
 		this.expiringTime.setTimeInMillis(calendar.getTimeInMillis());
 		this.expiringTime.add(Calendar.MILLISECOND, -1);
 		this.expiringTime.add(Calendar.MILLISECOND, expiringTimeout);
+		initialized = false;
 	}
 	
 	public void renew() throws ResourceRegistryException {
@@ -103,14 +107,17 @@ public class ContextCache {
 	
 	public synchronized void refreshContextsIfNeeded() throws ResourceRegistryException {
 		Calendar now = Calendar.getInstance();
-		if((now.after(expiringTime) || (contexts==null)) && contextCacheRenewal!=null) {
+		if((now.after(expiringTime) || (!initialized)) && contextCacheRenewal!=null) {
 			try {
 				List<Context> contexts = contextCacheRenewal.renew();
 				setContexts(now, contexts);
+				initialized = true;
 			} catch (ResourceRegistryException  e) {
-				logger.error("Unable to refresh Cache", e);
+				if(!initialized) {
-				if(contexts==null) {
+					logger.error("Unable to initialize Context Cache", e);
 					throw e;
+				}else {
+					logger.error("Unable to refresh Context Cache", e);
 				}
 			}
 			
@@ -129,7 +136,6 @@ public class ContextCache {
 	
 	protected void setContexts(Calendar calendar, List<Context> contexts) {
 		cleanCache(calendar);
-		this.contexts = new ArrayList<>();
 		
 		for(Context c : contexts) {
 			UUID uuid = c.getID();
@@ -232,7 +238,8 @@ public class ContextCache {
 		return new TreeMap<>(contextFullNameToUUID);
 	}
 	
-	public Tree<Context> getContextsTree() {
+	public Tree<Context> getContextsTree() throws ResourceRegistryException {
+		refreshContextsIfNeeded();
 		return contextsTree;
 	}