Logstash class and file and method display "?"

Elastic Stack Logstash
1 
 "_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": "?",

I would like to ask why class and file and method is a question mark it?

my logstash is below：

nput {

  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}"

  }

}
2

The Java bytecode is probably lacking debug symbols.