Logback custom pattern parameter resolution

demand

The logged in user name should be included in the printed log .

• The most stupid way ： Every time the log is printed , Add the user name manually
• workable proposition ： Intercept request , Write the user name to MDC, And then in Pattern Pass through %X{username} Print
• loading X The way to ： Intercept request , Write the user name to ThreadLocal, And then in Pattern Pass through %u Customized in this Pattern Print

Customize Pattern

append Configuration of

<appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
            <layout class="com.example.demo.log.UserLogbackLayout">
                <Pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%-10u] [%thread] %-5level %logger{36} -%msg%n</Pattern>
            </layout>
        </encoder>
    </appender>

Be careful Pattern Inside [%-10u], We just want to use %u To output the user name

UserLogbackLayout

public class UserLogbackLayout extends PatternLayout {
    
	//  Nothing , Is to register a pair of parameters u analytically converter
    static {
    
        DEFAULT_CONVERTER_MAP.put("u", LogbackUserPatternConverter.class.getName());
    }
}

LogbackUserPatternConverter

public class LogbackUserPatternConverter extends ClassicConverter {
    

    @Override
    public String convert(ILoggingEvent iLoggingEvent) {
    
    	//  Nothing , Just from ThreadLocal Fetching users from 
        return UserHolder.get();
    }
}

Test it

so easy！