Implementing Logging

logging:
  level:
    root: INFO
    com.example: DEBUG
    org.hibernate.SQL: DEBUG
    org.hibernate.type.descriptor.sql.BasicBinder: TRACE
    org.springframework.security: DEBUG

private static final Logger log = LoggerFactory.getLogger(OrderService.class);
log.info("Order placed id={} total={}", order.getId(), order.getTotal());
log.error("DB failure for order {}", id, ex); // exception last
if (log.isDebugEnabled()) log.debug("Heavy: {}", expensive());

<configuration>
  <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
  <springProperty name="appName" source="spring.application.name"/>
  <appender name="JSON" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="net.logstash.logback.encoder.LogstashEncoder"/>
  </appender>
  <springProfile name="prod">
    <root level="INFO"><appender-ref ref="JSON"/></root>
  </springProfile>
</configuration>

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter</artifactId>
  <exclusions>
    <exclusion>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-logging</artifactId>
    </exclusion>
  </exclusions>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

logging:
  file:
    name: /var/log/app.log
    path: /var/log
  pattern:
    file: "%d{ISO8601} %-5level [%thread] %logger{36} - %msg%n"

public class TraceFilter extends OncePerRequestFilter {
  @Override protected void doFilterInternal(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
      throws IOException, ServletException {
    String tid = Optional.ofNullable(req.getHeader("X-Trace-Id")).orElse(UUID.randomUUID().toString());
    MDC.put("traceId", tid);
    try { chain.doFilter(req, res); }
    finally { MDC.clear(); }
  }
}
// pattern: %X{traceId}

<dependency>
  <groupId>net.logstash.logback</groupId>
  <artifactId>logstash-logback-encoder</artifactId>
  <version>7.4</version>
</dependency>

log.atInfo()
   .setMessage("Order placed")
   .addKeyValue("orderId", id)
   .addKeyValue("total", total)
   .log();