JSONLayout

JSONLayout is a layout component used by several logging frameworks to format log events as JSON. It is designed to produce structured log entries that can be easily parsed by log collectors, analytics pipelines, and SIEM systems. A JSONLayout typically emits a JSON object for each log event and can be configured to include various pieces of information.

Common fields include timestamp (often in ISO-8601 or epoch milliseconds), severity level, logger name, thread name, and the rendered message. Many implementations also include the logger’s context data (MDC), exception stack traces, and location information (class, method, file, line). The layout can be configured to generate compact JSON or pretty-printed output, and to include or exclude optional fields depending on the deployment needs. It is commonly used with appenders such as console, file, socket, or syslog to produce machine-readable log data.

In practice, JSONLayout is closely associated with Log4j 2’s JsonLayout, where users configure the layout in configuration files (XML, JSON, YAML) and select options such as including stack traces, including time fields, and whether to include location information and properties. Other frameworks offer similar JSON-oriented layouts with varying feature sets. The primary goal is to enable structured logging that supports reliable ingestion into modern log analysis stacks.

Notes: When using JSONLayout, consider performance implications and the sensitivity of logged data, and ensure appropriate data redaction and access controls.