Logstash class file 和 method都是问号

 "_index": "meipianapp-2016.10.18",

  "_type": "log4j",

  "_id": "AVfXDMl1egLz1PD_qnMm",

  "_score": null,

  "_source": {

    "message": "用户查询时光祭异常:MjController.userMjActivityPast: aMapCityCode:010",

    "@version": "1",

    "@timestamp": "2016-10-18T09:08:41.324Z",

    "timestamp": 1476781719183,

    "path": "com.meipian.core.api.controller.MjActivityController",

    "priority": "ERROR",

    "logger_name": "com.meipian.core.api.controller.MjActivityController",

    "thread": "http-bio-8080-exec-6",

    "class": "?",

    "file": "?:?",

    "method": "?",

请问这是为什么？

我的logstash是这样配置的：

input {



  log4j {



    mode => "server"



    host => "0.0.0.0"



    port => 4567



    type => "log4j"



  }



}



    filter {



                date {



      match => [ "timestamp" , "dd/MMM/yyyy:HH:mm:ss +0800" ]



      timezone => "UTC"



           }



        }



output {



  elasticsearch {



     hosts=> ["10.105.103.125:9200"]



     index => "meipianapp-%{+YYYY.MM.dd}"



  }



}