序

本文主要研究一下logback的ThresholdFilter

ThresholdFilter

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

public class ThresholdFilter extends Filter<ILoggingEvent> {Level level;@Overridepublic FilterReply decide(ILoggingEvent event) {if (!isStarted()) {return FilterReply.NEUTRAL;}if (event.getLevel().isGreaterOrEqual(level)) {return FilterReply.NEUTRAL;} else {return FilterReply.DENY;}}public void setLevel(String level) {this.level = Level.toLevel(level);}public void start() {if (this.level != null) {super.start();}}
}

ThresholdFilter继承了Filter，其decide方法从ILoggingEvent获取level，若该level大于等于指定的level则返回NEUTRAL，否则返回DENY

isGreaterOrEqual

ch/qos/logback/classic/Level.java

public final class Level implements java.io.Serializable {private static final long serialVersionUID = -814092767334282137L;public static final int OFF_INT = Integer.MAX_VALUE;public static final int ERROR_INT = 40000;public static final int WARN_INT = 30000;public static final int INFO_INT = 20000;public static final int DEBUG_INT = 10000;public static final int TRACE_INT = 5000;public static final int ALL_INT = Integer.MIN_VALUE;/*** The <code>OFF</code> is used to turn off logging.*/public static final Level OFF = new Level(OFF_INT, "OFF");/*** The <code>ERROR</code> level designates error events which may or not be* fatal to the application.*/public static final Level ERROR = new Level(ERROR_INT, "ERROR");/*** The <code>WARN</code> level designates potentially harmful situations.*/public static final Level WARN = new Level(WARN_INT, "WARN");/*** The <code>INFO</code> level designates informational messages highlighting* overall progress of the application.*/public static final Level INFO = new Level(INFO_INT, "INFO");/*** The <code>DEBUG</code> level designates informational events of lower* importance.*/public static final Level DEBUG = new Level(DEBUG_INT, "DEBUG");/*** The <code>TRACE</code> level designates informational events of very low* importance.*/public static final Level TRACE = new Level(TRACE_INT, "TRACE");/*** The <code>ALL</code> is used to turn on all logging.*/public static final Level ALL = new Level(ALL_INT, "ALL");public final int levelInt;public final String levelStr;/*** Instantiate a Level object.*/private Level(int levelInt, String levelStr) {this.levelInt = levelInt;this.levelStr = levelStr;}/*** Returns <code>true</code> if this Level has a higher or equal Level than the* Level passed as argument, <code>false</code> otherwise.*/public boolean isGreaterOrEqual(Level r) {return levelInt >= r.levelInt;}//......
}    

Level定义了OFF(Integer.MAX_VALUE)、ERROR(40000)、WARN(30000)、INFO(20000)、DEBUG(10000)、TRACE(5000)、ALL(Integer.MIN_VALUE)这几个level，其int值依次减小。isGreaterOrEqual方法则是根据levelInt值来判断。

示例

	<appender name="FILE_INFO"class="ch.qos.logback.core.rolling.RollingFileAppender"><file>infoLog.log</file><rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"><fileNamePattern>infoLogs.%d{yyyy-MM-dd}.log</fileNamePattern><maxHistory>30</maxHistory><totalSizeCap>3GB</totalSizeCap></rollingPolicy><filter class="ch.qos.logback.classic.filter.ThresholdFilter"><level>INFO</level></filter><encoder><pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern></encoder></appender>

这里对FILE_INFO添加了ThresholdFilter，只有级别大于等于INFO的才打印

小结

logback的ThresholdFilter继承了Filter，其decide方法从ILoggingEvent获取level，若该level大于等于指定的level则返回NEUTRAL，否则返回DENY。Level定义了OFF(Integer.MAX_VALUE)、ERROR(40000)、WARN(30000)、INFO(20000)、DEBUG(10000)、TRACE(5000)、ALL(Integer.MIN_VALUE)这几个level，其int值依次减小。isGreaterOrEqual方法则是根据levelInt值来判断。