Log4j 的配置

迷南。 2021-09-22 09:08 347阅读 0赞

上一章介绍log4j的核心组件。本章介绍如何使用配置文件来配置这些核心组件。配置log4j涉及分配级别，定义追加程序，并在配置文件中指定布局的对象。

**Appenders:**

Apache的log4j提供Appender对象主要负责打印日志消息到不同的目的地，如控制台，文件，sockets，NT事件日志等等。每个Appender对象具有与之相关联的不同的属性，并且这些属性表明对象的行为，常用属性如下：

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    <div style=""> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">属性</span></span> 
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     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">描述</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">layout</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">Appender使用布局Layout&nbsp;对象和与之相关的格式化的日志记录信息转换模式</span></span> 
    </div> </td> 
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   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">target</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">目标可以是一个控制台，一个文件，或根据附加器的另一个项目</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">level</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">级别是必需的，以控制日志消息的过滤</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">threshold</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">Appender可以有与之独立的记录器级别相关联的级别阈值水平。Appender忽略具有级别低于阈级别的任何日志消息</span></span> 
    </div> </td> 
  </tr> 
  <tr style="height:40px"> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">filter</span></span> 
    </div> </td> 
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    <div style=""> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">Filter 对象可以分析超出级别的匹配记录信息，并决定是否记录的请求应该由一个特定&nbsp;Appender&nbsp;或忽略处理</span></span> 
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</table>

**根Logger**

根logger主要定义log4j支持的日志级别及输出目的地，其语法为：

log4j.rootLogger = \[ level \] , appenderName, appenderName, …

其中，level 是日志记录的优先级，分为OFF、FATAL、ERROR、WARN、INFO、DEBUG、ALL或者自定义的级别。

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     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">Level</span></span> 
    </div> </td> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">描述</span></span> 
    </div> </td> 
  </tr> 
  <tr style="height:40px"> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">ALL</span></span> 
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     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">各级包括自定义级别</span></span> 
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    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">DEBUG</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">指定细粒度信息事件是最有用的应用程序调试</span></span> 
    </div> </td> 
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   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">ERROR</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">错误事件可能仍然允许应用程序继续运行</span></span> 
    </div> </td> 
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   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">FATAL</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">指定非常严重的错误事件，这可能导致应用程序中止</span></span> 
    </div> </td> 
  </tr> 
  <tr style="height:40px"> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">INFO</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">指定能够突出在粗粒度级别的应用程序运行情况的信息的消息</span></span> 
    </div> </td> 
  </tr> 
  <tr style="height:40px"> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">OFF</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">这是最高等级，为了关闭日志记录</span></span> 
    </div> </td> 
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   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">TRACE</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">指定细粒度比DEBUG更低的信息事件</span></span> 
    </div> </td> 
  </tr> 
  <tr style="height:40px"> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">WARN</span></span> 
    </div> </td> 
   <td style="color:rgb(57,57,57); border:1px solid rgb(167,167,167); overflow:hidden; vertical-align:middle; word-wrap:break-word; white-space:pre-wrap"> 
    <div> 
     <span style="font-family:&quot;Microsoft YaHei&quot;,STXihei; color:rgb(0,0,0); background-color:transparent"><span style="font-size:14px">指定具有潜在危害的情况</span></span> 
    </div> </td> 
  </tr> 
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</table>

建议只使用四个级别，优先级从高到低分别是ERROR、WARN、INFO、DEBUG。

appenderName指定日志信息输出到哪个地方，可同时指定多个输出目的地。

**配置输出目的地Appender**

Appender主要定义日志信息输出在什么位置，主要语法为：

log4j.appender.appenderName = classInfo log4j.appender.appenderName.option1 = value1 …... log4j.appender.appenderName.optionN = valueN

Log4j提供的appender有以下几种：

•org.apache.log4j.ConsoleAppender（控制台），  
•org.apache.log4j.FileAppender（文件），  
•org.apache.log4j.DailyRollingFileAppender（每天产生一个日志文件），  
•org.apache.log4j.RollingFileAppender（文件大小到达指定尺寸的时候产生一个新的文件）  
•org.apache.log4j.WriterAppender（将日志信息以流格式发送到任意指定的地方）

**配置日志信息的格式Layout**

Layout 负责格式化Appender的输出，其语法为：

log4j.appender.appenderName.layout = classInfo log4j.appender.appenderName.layout.option1 = value1 … log4j.appender.appenderName.layout.optionN = valueN

其中，Log4j提供的layout有以下几种：

**设置package输出级别**

可以设置不同package的日志输出级别，语法为：

log4j.logger.packageName=level

其中，packageName为实际的包名，level为日志级别，例如：

log4j.logger.org.springframework=info log4j.logger.org.apache.catalina=info log4j.logger.org.apache.commons.digester.Digester=info log4j.logger.org.apache.catalina.startup.TldConfig=info log4j.logger.chb.test=debug

**Log4j配置方式**

通过上面的介绍，我们已经大概清楚了配置Log4j所需要的内容，Log4j可以通过java程序动态设置，该方式缺点是：如果需要修改日志输出级别等信息，则必须修改java文件，然后重新编译，很是麻烦。log4j也可以通过配置文件的方式进行设置，目前支持两种格式的配置文件：

•properties文件（推荐）

•xml文件

以下是 log4j.properties 文件的一个样例语法：

# Define the root logger with appender X
    log4j.rootLogger = DEBUG, X
     # Set the appender named X to be a File appender
    log4j.appender.X=org.apache.log4j.FileAppender
    # Define the layout for X appender
    log4j.appender.X.layout=org.apache.log4j.PatternLayout
    log4j.appender.X.layout.conversionPattern=%m%n

使用上面的语法，我们定义 log4j.properties 文件如下：  
● 根日志记录器(logger)的级别定义为DEBUG并连接附加器命名为FILE  
● 附加器(appender)File是定义为org.apache.log4j.FileAppender并写入到一个名为“log.out”位于日志log目录下

● 定义的布局模式是%m%n，这意味着每打印日志消息之后，将加上一个换行符

# Define the root logger with appender file 
      log=D:/log4j
    log4j.rootCategory=INFO, file
    log4j.rootLogger = INFO,file
    
    # Define the file appender
    log4j.appender.file=org.apache.log4j.FileAppender
    log4j.appender.file.File=${log}/log.out
    
    # Define the layout for file appender
    log4j.appender.file.layout=org.apache.log4j.PatternLayout
    log4j.appender.file.layout.conversionPattern=%m%n

再写一个复杂点的，这个在实际项目中用的比较多

#设置等级和Appender。 log4j.rootLogger=debug,appender1,apppender2 #定义appender1属性和布局 #附加器(appender) appender1定义为控制台输出 log4j.appender. appender1= org.apache.log4j.ConsoleAppender log4j.appender. appender1.layout=org.apache.log4j.PatternLayout log4j.appender. appender1.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n #定义appender2属性和布局 #appender2定义为文件输出 log4j.appender. appender2=org.apache.log4j.RollingFileAppender log4j.appender.apppender2.File=example.log log4j.appender.appender2.MaxFileSize=100KB log4j.appenderappender2.MaxBackupIndex=1 log4j.appender.appender2.layout=org.apache.log4j.PatternLayout log4j.appender.appender2.layout.ConversionPattern=%p %t %c - %m%n #输出日志的格式和信息都是可配可选的。

参考：

[http://zhaoyanblog.com/archives/167.html][http_zhaoyanblog.com_archives_167.html]

[http://www.yiibai.com/log4j/log4j\_configuration.html][http_www.yiibai.com_log4j_log4j_configuration.html]

[http://www.jb51.net/article/41001.htm][http_www.jb51.net_article_41001.htm]

[http_zhaoyanblog.com_archives_167.html]: http://zhaoyanblog.com/archives/167.html
[http_www.yiibai.com_log4j_log4j_configuration.html]: http://www.yiibai.com/log4j/log4j_configuration.html
[http_www.jb51.net_article_41001.htm]: http://www.jb51.net/article/41001.htm