Structured Logging

package org.slf4j;

public interface Logger {
    String getName();

    boolean isTraceEnabled();
    void trace(String msg);
    void trace(String format, Object arg);
    void trace(String format, Object arg1, Object arg2);
    void trace(String format, Object... arguments);
    void trace(String msg, Throwable t);

    boolean isDebugEnabled();
    void debug(String msg);
    ...

    boolean isInfoEnabled();
    void info(String msg);
    ...

    boolean isWarnEnabled();
    void warn(String msg);
    ...

    boolean isErrorEnabled();
    void error(String msg);
    ...
}

logging.level.root=DEBUG

dependencies {
	implementation "org.springframework.boot:spring-boot-starter-log4j2"
	modules {
		module("org.springframework.boot:spring-boot-starter-logging") {
			replacedBy("org.springframework.boot:spring-boot-starter-log4j2", "Use Log4j2 instead of Logback")
		}
	}
}

logging.structured.format.console=ecs
logging.structured.format.file=ecs

{
  "@timestamp": "2025-02-25T12:00:00.123Z",
  "log.level": "INFO",
  "message": "User login successful",
  "event.category": "authentication",
  "event.action": "user_login",
  "user.id": "567",
  "user.name": "john_doe",
  "http.request.method": "POST",
  "http.response.status_code": 200
}

logging.structured.format.console=gelf
logging.structured.format.file=gelf

{
  "version": "1.1",
  "host": "server-1",
  "short_message": "User login successful",
  "full_message": "User john_doe logged in from IP 192.168.1.100",
  "timestamp": 1708886400.123,
  "level": 6,
  "_user_id": "567",
  "_ip_address": "192.168.1.100",
  "_http_method": "POST"
}

logging.structured.format.console=logstash
logging.structured.format.file=logstash

{
  "timestamp": "2025-02-25T12:00:00.123Z",
  "level": "INFO",
  "message": "User login successful",
  "service": "UserService",
  "user_id": "567",
  "ip_address": "192.168.1.100",
  "http_method": "POST"
}

logging.structured.format.console=logstash

@Component  
public class JsonLogFilter implements Filter {  
  
    @Override  
    public void doFilter(final ServletRequest request, final ServletResponse response,  
        final FilterChain chain)  
        throws IOException, ServletException {  
  
        try {  
            String userId = "example userId";  
            MDC.put("user.id", userId);  
            chain.doFilter(request, response);  
        } finally {  
            MDC.clear();  
        }  
    }  
}

{
   "@timestamp":"2025-02-25T23:26:59.796577+09:00",
   "@version":"1",
   "message":"test log",
   "logger_name":"com.example.javacicdpractice.member.MemberController",
   "thread_name":"http-nio-8080-exec-1",
   "level":"INFO",
   "level_value":20000,
   "user.id":"example userId"
}