logback的LevelFilter日志过滤器源码解读

public abstract class AbstractMatcherFilter<E> extends Filter<E> {
    protected FilterReply onMatch = FilterReply.NEUTRAL;
    protected FilterReply onMismatch = FilterReply.NEUTRAL;
    final public void setOnMatch(FilterReply reply) {
        this.onMatch = reply;
    }
    final public void setOnMismatch(FilterReply reply) {
        this.onMismatch = reply;
    }
    final public FilterReply getOnMatch() {
        return onMatch;
    }
    final public FilterReply getOnMismatch() {
        return onMismatch;
    }
}

public class LevelFilter extends AbstractMatcherFilter<ILoggingEvent> {
    Level level;
    @Override
    public FilterReply decide(ILoggingEvent event) {
        if (!isStarted()) {
            return FilterReply.NEUTRAL;
        }
        if (event.getLevel().equals(level)) {
            return onMatch;
        } else {
            return onMismatch;
        }
    }
    public void setLevel(Level level) {
        this.level = level;
    }
    public void start() {
        if (this.level != null) {
            super.start();
        }
    }
}

<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>ERROR</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
        <encoder>
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
        </encoder>
    </appender>