VFS - CacheStragey
One problem with libraries like vfs is that they cache some data to avoid successive access to the real file - simply to speed up things.
This cache might get stale - no it GET stale.
Currently VFS provides three strategies to workaround it:
- on resolve (the default)
- on call
Note: It is not possible to use VFS.getManager to configure the cacheStrategy. You have to create your own static class to create it.
manual cache strategy
StandardFileSystemManager fs = new StandardFileSystemManager(); fs.setCacheStrategy(CacheStrategy.MANUAL); fs.init();
using this setup you have to use fileObject.refresh() to refresh your object with the filesystem
StandardFileSystemManager fs = new StandardFileSystemManager(); fs.setCacheStrategy(CacheStrategy.ON_RESOLVE); fs.init();
every time you call fs.resolveFile() the file data will be refreshed. You still can use fileObject.refresh() to refresh the data on demand.
StandardFileSystemManager fs = new StandardFileSystemManager(); fs.setCacheStrategy(CacheStrategy.ON_CALL); fs.init();
Every time you call a method on the resolve file object the data will be refreshed with the filesystem. This will give you the behaviour you might expect from a local file but also might be a hughe performance loss as it will greatly increase the network load.
You can also achieve this cache strategy by wrapping the file object in an org.apache.commons.vfs.cache.OnCallRefreshFileObject
FileObject fo = VFS.getManager().resolveFile("...."); OnCallRefreshFileObject foc = new OnCallRefreshFileObject(fo);
The difference to the above is, that in the first case you will always get the same file object instance and thus you can synchronize on it.