Hadoop中元数据生成的作用和源代码以及操作示例是什么？

 
protected Path createInputFileListing(Job    job) throws IOException {

    Path    fileListingPath = getFileListingPath();

    CopyListing    copyListing = CopyListing.getCopyListing(job.getConfiguration(),

           job.getCredentials(), inputOptions);

    copyListing.buildListing(fileListingPath,    inputOptions);

    return    fileListingPath;

}