Summary - Logging

Combine logging, levels and handlers to write a log system.

Summary - Logging

In this group we learned logging management with Dart. The logging package holds logs; Level (SEVERE, WARNING, INFO, FINE) filters; Logger works with hierarchical names; handler processes records; structured logging produces machine-friendly JSON output.

In this summary we bring all parts together with structured logging. The program sets up a logger, produces JSON records via a handler and writes an info record. This is a small but working example of a real application's logging layer.

Exercise Structured logging summary

Add import 'dart:convert'; and import 'package:logging/logging.dart';. In main add Logger.root.level = Level.INFO; and a handler: Logger.root.onRecord.listen((r) { final record = jsonEncode({'logger': r.loggerName, 'level': r.level.name, 'msg': r.message}); print(record); });. Create final log = Logger('summary'); and call log.info('done').

Show example solution

import 'dart:convert';
import 'package:logging/logging.dart';

void main() {
  Logger.root.level = Level.INFO;
  Logger.root.onRecord.listen((r) {
    final record = jsonEncode({'logger': r.loggerName, 'level': r.level.name, 'msg': r.message});
    print(record);
  });
  final log = Logger('summary');
  log.info('done');
}

Test yourself

Which is the standard logging package?
- sqflite
- logging
- args
- dcli
Show answer

logging — logging is Dart's standard logging package.
Match the logging concepts

logging

Package
Level

Level
Logger

Logger
onRecord

Handler stream

The jsonEncode call

final record = ____({'logger': r.loggerName, 'level': r.level.name, 'msg': r.message});

Show answer

final record = jsonEncode({'logger': r.loggerName, 'level': r.level.name, 'msg': r.message});

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