log4j2 config

      <JsonTemplateLayout eventTemplateUri="file:/path/to/MyLayout.json" stackTraceEnabled="true">
        <EventTemplateAdditionalFields>
        </EventTemplateAdditionalFields>
      </JsonTemplateLayout>

log_output

{"@timestamp":"2020-12-11T01:49:26.490Z","level":"ERROR","message":"org.apache.solr.common.SolrException: undefined field _text_\n\tat org.apache.solr.schema.IndexSchema.getDynamicFieldType(IndexSchema.java:1305)\n\tat org.apache.solr.schema.IndexSchema$SolrQueryAnalyzer.getWrappedAnalyzer(IndexSchema.java:442)\n\tat 
...
java.base/java.lang.Thread.run(Thread.java:834)\n","thread":"qtp1492875057-241","stack":"org.apache.logging.slf4j.Log4jLogger"}

MyLayout.json

{
  "@timestamp": {
    "$resolver": "timestamp",
    "pattern": {
      "format": "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'",
      "timeZone": "UTC"
    }
  },
  "level": {
    "$resolver": "level",
    "field": "name"
  },
  "message": {
    "$resolver": "message",
    "stringified": true,
    "includeStackTrace": false
  },
  "thread": {
    "$resolver": "thread",
    "field": "name"
  },
  "stack": {
    "$resolver": "logger",
    "field": "fqcn"
  },
  "labels": {
    "$resolver": "mdc",
    "flatten": true,
    "stringified": true
  },
  "tags": {
    "$resolver": "ndc"
  },
  "error.type": {
    "$resolver": "exception",
    "field": "className"
  },
  "error.message": {
    "$resolver": "exception",
    "field": "message"
  },
  "root_cause": {
    "$resolver": "exceptionRootCause",
    "field": "stackTrace",
    "stringified": true
  }
}