聊聊logback的LevelFilter

序

本文主要研究一下logback的LevelFilter

AbstractMatcherFilter

ch/qos/logback/core/filter/AbstractMatcherFilter.java

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;}
}

AbstractMatcherFilter继承了Filter，它定义了onMatch及onMismatch属性

LevelFilter

ch/qos/logback/classic/filter/LevelFilter.java

public class LevelFilter extends AbstractMatcherFilter<ILoggingEvent> {Level level;@Overridepublic 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();}}
}

LevelFilter继承了AbstractMatcherFilter，其decide判断event的level等级是否与配置的level一致，一致则返回onMatch，否则返回onMismatch

示例

    <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>

这里CONSOLE的appender定义了LevelFilter，当level为ERROR级别时ACCEPT，否则DENY

小结

logback提供了LevelFilter，可以配置指定的level、onMatch、onMismatch属性，用于设置指定appender的打印级别。