(六)Logback中的Filter

小灰灰 2022-02-03 23:15 309阅读 0赞

一、Logback中Filter的种类

在logback-classic中，提供了两种类型的filter：regular过滤器和turbo过滤器。

1、Regular过滤器

规律型过滤器继承自[Filter][]抽象类，该类主要由带有ILoggingEvent参数的decide()方法组成。多个过滤器会基于三进制规则进行排序，每个过滤器的decide(ILoggingEvent event)方法依次会被调用，该方法返回[FilterReply][]的枚举值，例如：DENY、NEUTRAL、ACCEPT。如果方法返回值为DENY，那么日志对象会被终止而不会被其它过滤器访问。如果方法返回值为NEUTRAL，那么下一个过滤器会进行处理，如果没有其余过滤器，那么日志会被正常处理。如果方法返回值为ACCEPT，那么日志对象会跳过其余过滤器被立即处理。

1.1 自定义过滤器

package chapters.filters;
    
    import ch.qos.logback.classic.spi.ILoggingEvent;
    import ch.qos.logback.core.filter.Filter;
    import ch.qos.logback.core.spi.FilterReply;
    
    public class SampleFilter extends Filter<ILoggingEvent> {
    
      @Override
      public FilterReply decide(ILoggingEvent event) {    
        if (event.getMessage().contains("sample")) {
          return FilterReply.ACCEPT;
        } else {
          return FilterReply.NEUTRAL;
        }
      }
    }

logback配置文件如下：

<configuration>
      <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    
        <filter class="chapters.filters.SampleFilter" />
    
        <encoder>
          <pattern>
            %-4relative [%thread] %-5level %logger - %msg%n
          </pattern>
        </encoder>
      </appender>
            
      <root>
        <appender-ref ref="STDOUT" />
      </root>
    </configuration>

1.2 LevelFilter(级别过滤器)

[LevelFilter][]基于匹配的具体级别过滤事件，如果日志事件的级别等于配置的级别，那么过滤器会接受或者拒绝日志事件，这取决于配置的onMatch和onMisMatch属性，如下：

<configuration>
      <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
          <level>INFO</level>
          <onMatch>ACCEPT</onMatch>
          <onMismatch>DENY</onMismatch>
        </filter>
        <encoder>
          <pattern>
            %-4relative [%thread] %-5level %logger{30} - %msg%n
          </pattern>
        </encoder>
      </appender>
      <root level="DEBUG">
        <appender-ref ref="CONSOLE" />
      </root>
    </configuration>

1.3 ThresholdFilter(阀值过滤器)

[ThresholdFilter][]会过滤低于指定阀值的日志事件，对于等于或者大于阀值的日志事件，该过滤器会响应NEUTRAL，而对于低于阀值的日志事件，改过滤器会响应DENY。如下：

<configuration>
      <appender name="CONSOLE"
        class="ch.qos.logback.core.ConsoleAppender">
        
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
          <level>INFO</level>
        </filter>
        <encoder>
          <pattern>
            %-4relative [%thread] %-5level %logger{30} - %msg%n
          </pattern>
        </encoder>
      </appender>
      <root level="DEBUG">
        <appender-ref ref="CONSOLE" />
      </root>
    </configuration>

1.4 其它过滤器

[EvaluatorFilter][]：这是包装了EventEvaluator的通用过滤器，见名知义，[EventEvaluator][]会根据指定条件是否满足对日志事件进行判断是接收还是拒绝，该过滤器是一个抽象类。

该过滤器具体实现有：

[GEventEvaluator][]：基于Groovy语言布尔表达式作为判断条件。

[JaninoEventEvaluator][]：基于返回布尔值的Java语言块作为判断条件，具体配置参考[配置表][Link 1]。

示例1：GEventEvaluator

<configuration>
        
      <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.core.filter.EvaluatorFilter">      
          <evaluator class="ch.qos.logback.classic.boolex.GEventEvaluator"> 
            <expression>
               e.level.toInt() >= WARN.toInt() &&  
               !(e.mdc?.get("req.userAgent") =~ /Googlebot|msnbot|Yahoo/ )
            </expression>
          </evaluator>
          <OnMismatch>DENY</OnMismatch>
          <OnMatch>NEUTRAL</OnMatch>
        </filter>
        <encoder>
          <pattern>
            %-4relative [%thread] %-5level %logger - %msg%n
          </pattern>
        </encoder>
      </appender>
    
      <root level="DEBUG">
        <appender-ref ref="STDOUT" />
      </root>
    </configuration>

示例2：JanioEventEvaluator

<configuration>
    
      <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.core.filter.EvaluatorFilter">      
          <evaluator> 
            <expression>return message.contains("billing");</expression>
          </evaluator>
          <OnMismatch>NEUTRAL</OnMismatch>
          <OnMatch>DENY</OnMatch>
        </filter>
        <encoder>
          <pattern>
            %-4relative [%thread] %-5level %logger - %msg%n
          </pattern>
        </encoder>
      </appender>
    
      <root level="INFO">
        <appender-ref ref="STDOUT" />
      </root>
    </configuration>

[Filter]: https://logback.qos.ch/xref/ch/qos/logback/core/filter/Filter.html
[FilterReply]: https://logback.qos.ch/xref/ch/qos/logback/core/spi/FilterReply.html
[LevelFilter]: https://logback.qos.ch/xref/ch/qos/logback/classic/filter/LevelFilter.html
[ThresholdFilter]: https://logback.qos.ch/xref/ch/qos/logback/classic/filter/ThresholdFilter.html
[EvaluatorFilter]: https://logback.qos.ch/xref/ch/qos/logback/core/filter/EvaluatorFilter.html
[EventEvaluator]: https://logback.qos.ch/xref/ch/qos/logback/core/boolex/EventEvaluator.html
[GEventEvaluator]: https://logback.qos.ch/xref/ch/qos/logback/classic/boolex/GEventEvaluator.html
[JaninoEventEvaluator]: https://logback.qos.ch/xref/ch/qos/logback/classic/boolex/JaninoEventEvaluator.html
[Link 1]: https://logback.qos.ch/manual/filters.html#JaninoEventEvaluator