server/src/main/java/envoy/server/data/PersistenceManager.java

@@ -341,15 +341,36 @@ public final class PersistenceManager {
 	}
 
 	private void persist(Object obj) {
+		try {
 			transaction(() -> entityManager.persist(obj));
+		} catch (EntityExistsException e) {
+			if (transaction.isActive())
+				transaction.rollback();
+			EnvoyLog.getLogger(PersistenceManager.class).log(Level.WARNING,
+				String.format("Could not persist %s: entity exists already.", obj));
+		}
 	}
 
 	private void merge(Object obj) {
+		try {
 			transaction(() -> entityManager.merge(obj));
+		} catch (IllegalArgumentException e) {
+			if (transaction.isActive())
+				transaction.rollback();
+			EnvoyLog.getLogger(PersistenceManager.class).log(Level.WARNING,
+				String.format("Could not merge %s: entity doesn't exist.", obj));
+		}
 	}
 
 	private void remove(Object obj) {
+		try {
 			transaction(() -> entityManager.remove(obj));
+		} catch (IllegalArgumentException e) {
+			if (transaction.isActive())
+				transaction.rollback();
+			EnvoyLog.getLogger(PersistenceManager.class).log(Level.WARNING,
+				String.format("Could not remove %s: entity didn't exist (for the database).", obj));
+		}
 	}
 
 	/**