Abstract: Metadata plays a very important role in Web application．With the increasing scale of metadata,maintaining metadata will spend intensive time and effort．The current compiler cannot notify the faults caused by metadata inconsistency,and the relationship between metadata and codebase is hidden．This paper extracted all the invariance of the projects based on the research regarding with the metadata invariant by experiments．It illustrated that the metadata invariants are respectively extracted and compared through such different methods as framework-based invariant discovering and frameless-based invariant discovering．When the program is refactored or enhanced,the metadata invariance will be determined．A message will be given if the programs violate invariance．

Key words: Metadata,Invariance,Java,Software testing,Software bugs