gistfile1.txt

Resource transactions
The resources API provides a transaction service on FileResources. If you are familiar with UserTransaction in Java EE applications, this should feel pretty comfortable.

ResourceTransaction transaction = factory.getTransaction();
try {
   // Starts the transaction
   transaction.begin();

   FileResource<?> resource = factory.create(...);
   // The file won't be updated until commit is performed
   resource.setContents("Hello World");

   String contents = resource.getContents(); // Returns "Hello World"

   FileResource<?> anotherResource = factory.create(...);
   // The file won't be deleted until commit is performed
   anotherResource.delete();

   FileResource<?> newResource = factory.create(...);
   // The file won't be created until commit is performed
   newResource.createNewFile();

   transaction.commit();
} catch (Exception e){
    // Discard all changes since the beginning of this transaction
    transaction.rollback();
}
Additionally, transactions support change-set inspection, so you can compare file contents before deciding whether or not a given transaction should be committed or rolled back:

   ...
   Collection<ResourceEvent> changeSet = transaction.getChangeSet();
   ...
   transaction.commit();
According to the above example, this change set contains the following entries:

Collection [
    ResourceModified: <DirectoryResource>,
    ResourceCreated: <FileResource<?>>,
    ResourceModified: <FileResource<?>>,
    ResourceDeleted: <FileResource<?>>,
    ResourceCreated: <FileResource<?>>
]