If you want to see the 'path' in the UI, you can use the Properties
plugin, available in the MITK Workbench and in your own app if you decided to include it.
If you want to access the content of the 'path' property in the code, then you need a mitk::DataNode
in the current scope, because properties are usually related to node.
std::string path;
node->GetStringProperty("path", path);
Note that this won't give you the full path though. For some reason, MITK decided to remove the extension in this property, thus giving something like D://Data/brain
instead of the D://Data/brain.nii.gz
that I wanted.
AFAIK, there's currently no 100% safe way to get the real full path in MITK, but one could easily search on the file system using path + ".*"
and hoping that it returns only one result :)