log4j的xml輸出配置

原來一直使用log4j.properties，發現它比properties功能強大，可以配置輸出多個log文件。

log4j 有兩種配置方法，大家熟知的是properties文件但是最近的項目實施中，每次去用戶那裏裝系統，都要苦惱於log文件放在不同位置，要改property文件就要重打jar包，麻煩的緊。而如果採用 xml配置的方法，直接放在WEB-INFO下，要修改路徑，很方便。查了些資料，終於把系統的log4j改成在xml中配置啦。

附：log4j的API http://logging.apache.org/log4j/docs/api/index.html
log4i.xml 文件

<?xml version="1.0" encoding="GB2312" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 <appender name="FILE"
  class="org.apache.log4j.RollingFileAppender">
  <!-- 設置通道file和輸出方式：org.apache.log4j.RollingFileAppender -->
  <param name="File" value="D:/zhaotj/all.output.log" /><!-- 設置File參數：日誌輸出文件名 -->
  <param name="Append" value="true" /><!-- 設置是否在重新啓動服務時，在原有日誌的基礎添加新日誌 -->
  <param name="MaxBackupIndex" value="10" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%p (%c:%L)- %m%n" /><!-- 設置輸出文件項目和格式 -->
  </layout>
 </appender>

 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
                <!-- 設置監視器輸出方式 -->
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern"
    value="%-4r [%t] %-5p %c %x - %m%n" />
  </layout>
                <!--濾鏡設置輸出的級別-->
  <filter class="org.apache.log4j.varia.LevelRangeFilter">
   <param name="levelMin" value="info" />
   <param name="levelMax" value="info" />
   <param name="AcceptOnMatch" value="true" />
  </filter>
 </appender>

 <root><!-- 設置接收所有輸出的通道 -->
  <priority value="info" />
  <appender-ref ref="FILE" /><!-- 與前面的通道id相對應 -->
  <appender-ref ref="STDOUT" />
 </root>

</log4j:configuration>

建好xml文件後要寫一個servlet類繼承actionservlet，當工程初始化時自動加載xml配置文件

package com.asiainfo;
import javax.servlet.ServletException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.xml.DOMConfigurator;
import org.apache.struts.action.ActionServlet;

public class ExtendedActionServlet extends ActionServlet {
        private Log log = LogFactory.getLog(this.getClass().getName());

        public ExtendedActionServlet() {}

        public void init() throws ServletException {
            log.info(
                    "Initializing, My MyActionServlet init this System's Const Variable");
            String prefix = this.getServletConfig().getServletContext().getRealPath(
                    "/");//讀取項目的路徑
            String file = this.getServletConfig().getInitParameter("log4j");
                       //讀取log4j相對路徑
            String filePath = prefix + file;
            DOMConfigurator.configure(filePath);//加載.xml文件      
            log.info("Initializing, end My Init");
            super.init();//應用了struts,此方法不能省，ActionServlet覆蓋了的此方法中有很多重要操作
        }
}

我們可以看到在此類中用了相對路徑來加載xml的方法，首先通過prefix 讀取了項目的路徑然後再通過讀取web.xml中的log4j變量，獲得log4j.xml的相對路徑兩者結合就是他的絕對路徑拉
最後在web.xml中配置action信息就可以實現加載啦
web.xml

<servlet>
  <servlet-name>action</servlet-name>
  <servlet-class>
   com.asiainfo.ExtendedActionServlet
  </servlet-class>
  <init-param>
   <param-name>config</param-name>
   <param-value>/WEB-INF/struts-config.xml</param-value>
  </init-param>

  <!-- tsExtend  -->
  <init-param>
   <param-name>config/tsextend</param-name><!--設備檢測子模塊-->
   <param-value>
    /WEB-INF/tsextend/struts-config.xml
   </param-value>
  </init-param>
                <init-param>
   <param-name>log4j</param-name><!--log4j.xml的路徑-->
   <param-value>
    /WEB-INF/log4j.xml
   </param-value>
  </init-param>
  <init-param>
   <param-name>info</param-name>
   <param-value>3</param-value>
  </init-param>
  <init-param>
   <param-name>detail</param-name>
   <param-value>3</param-value>
  </init-param>
  <load-on-startup>0</load-on-startup><!--設置當工程初始時便執行-->
 </servlet>

 <servlet-mapping>
  <servlet-name>action</servlet-name>
  <url-pattern>*.do</url-pattern>
 </servlet-mapping>

依據各個級別的日誌輸出到不同文件

log4j支持這個功能，不過不能再使用Properties配置，必須使用XML

建一個log4j.xml

<?xml   version= "1.0 "   encoding= "UTF-8 "?>
<!DOCTYPE   log4j:configuration   SYSTEM   "log4j.dtd ">
<log4j:configuration   xmlns:log4j= "http://jakarta.apache.org/log4j/ ">
<appender   name= "STDOUT "   class= "org.apache.log4j.ConsoleAppender ">
<layout   class= "org.apache.log4j.PatternLayout "/>
</appender>
<appender   name= "DEBUG "   class= "org.apache.log4j.RollingFileAppender ">
<param   name= "File "   value= "debug.log "/>
<param   name= "Append "   value= "true "/>
<param   name= "MaxFileSize "   value= "500KB "/>
<param   name= "MaxBackupIndex "   value= "2 "/>
<layout   class= "org.apache.log4j.PatternLayout "/>
<filter   class= "org.apache.log4j.varia.LevelRangeFilter ">
<param   name= "LevelMax "   value= "DEBUG "   />
<param   name= "LevelMin "   value= "DEBUG "   />
</filter>
</appender>
<appender   name= "INFO "   class= "org.apache.log4j.RollingFileAppender ">
<param   name= "File "   value= "info.log "/>
<param   name= "Append "   value= "true "/>
<param   name= "MaxFileSize "   value= "500KB "/>
<param   name= "MaxBackupIndex "   value= "2 "/>
<layout   class= "org.apache.log4j.PatternLayout "/>
<filter   class= "org.apache.log4j.varia.LevelRangeFilter ">
<param   name= "LevelMax "   value= "INFO "   />
<param   name= "LevelMin "   value= "INFO "   />
</filter>
</appender>
<root>
<appender-ref   ref= "STDOUT "/>
<appender-ref   ref= "DEBUG "/>
<appender-ref   ref= "INFO "/>
</root>
</log4j:configuration>