Make sure migration from PersisterService works

this.getClass() and this.class kept resolving to Class.
Using a string is much simpler

mkdirs() is also necessary because the directory structure doesn't exist
 when persistFile is called the first time

core/src/main/groovy/com/muwire/core/Core.groovy

@@ -264,6 +264,7 @@ public class Core {
         log.info "initializing folder persistence service"
         persisterFolderService = new PersisterFolderService(new File(home, "files"), eventBus)
         eventBus.register(PersisterDoneEvent.class, persisterFolderService)
+        eventBus.register(FileLoadedEvent.class, persisterFolderService)
         eventBus.register(FileHashedEvent.class, persisterFolderService)
         eventBus.register(FileUnsharedEvent.class, persisterFolderService)
 

core/src/main/groovy/com/muwire/core/files/BasePersisterService.groovy

@@ -53,7 +53,7 @@ abstract class BasePersisterService extends Service{
             Set<Destination> sourceSet = sources.stream().map({ d -> new Destination(d.toString())}).collect Collectors.toSet()
             DownloadedFile df = new DownloadedFile(file, ih, pieceSize, sourceSet)
             df.setComment(json.comment)
-            return new FileLoadedEvent(loadedFile : df, sourceClass : this.class)
+            return new FileLoadedEvent(loadedFile : df, source : "PersisterService")
         }
 
 
@@ -71,7 +71,7 @@ abstract class BasePersisterService extends Service{
                 sf.hit(searcher, timestamp, query)
             }
         }
-        return new FileLoadedEvent(loadedFile: sf, sourceClass: this.class)
+        return new FileLoadedEvent(loadedFile: sf, source : "PersisterService")
 
     }
 

core/src/main/groovy/com/muwire/core/files/FileLoadedEvent.groovy

@@ -6,5 +6,5 @@ import com.muwire.core.SharedFile
 class FileLoadedEvent extends Event {
 
     SharedFile loadedFile
-    Class sourceClass
+    String source
 }

core/src/main/groovy/com/muwire/core/files/PersisterFolderService.groovy

@@ -68,8 +68,9 @@ class PersisterFolderService extends BasePersisterService {
         }
     }
     void onFileLoadedEvent(FileLoadedEvent loadedEvent) {
-        if(loadedEvent.sourceClass == PersisterService){
-            log.info("Migrating persisted file from PersisterService")
+        if(loadedEvent.source == "PersisterService"){
+            log.info("Migrating persisted file from PersisterService: "
+                    + loadedEvent.loadedFile.file.absolutePath.toString())
             persistFile(loadedEvent.loadedFile)
         }
     }
@@ -124,7 +125,7 @@ class PersisterFolderService extends BasePersisterService {
             def jsonPath = getJsonPath(sf)
 
             def startTime = System.currentTimeMillis()
-            jsonPath.parent.toFile().mkdir()
+            jsonPath.parent.toFile().mkdirs()
             jsonPath.toFile().withPrintWriter { writer ->
                 def json = toJson sf
                 json = JsonOutput.toJson(json)