我在mongodb数据库中有以下gridfs:db.outputFs.files.find(){"_id":ObjectId("000000000000000000000001"),"chunkSize":261120,"length":232,"md5":"42290309186cc5420acff293b92ae21d","filename":"/tmp/outputFs-01.tmp","contentType":null,"uploadDate":ISODate("2015-04-13T13:50:48.259Z"),"aliases":null,"metadata":{"es