[Java] Log4j

[Abdujaparov]

Ciao a tutti,
ho da poco scaricato jboss5 e stavo cercando di capirne il funzionamento.
Ho visto che ha già di suo log4j che non conosco, ma a quanto ho capito serve per il log di jboss e permette di visualizzare gli errori di jboss. A quanto mi pare di aver capito all'interno del file jboss-log4j.xml vengono definiti degli appender sui quali scrivere il log. Più di questo non ho capito.

Nel file xml ho trovato questo:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<!-- ===================================================================== -->
<!--                                                                       -->
<!--  Log4j Configuration                                                  -->
<!--                                                                       -->
<!-- ===================================================================== -->

<!-- $Id: log4j.xml 64096 2007-07-17 14:36:23Z stan.silvert@jboss.com $ -->

<!--
   | For more configuration information and examples see the Jakarta Log4j
   | owebsite: http://jakarta.apache.org/log4j
 -->

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">

   <!-- ================================= -->
   <!-- Preserve messages in a local file -->
   <!-- ================================= -->

   <!-- A time/date based rolling appender -->
   <appender name="FILE" class="org.jboss.logging.appender.DailyRollingFileAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      <param name="File" value="${jboss.server.log.dir}/server.log"/>
      <param name="Append" value="false"/>
      <!-- 
         Set the threshold via a system property. Note this is parsed by log4j,
         so the full JBoss system property format is not supported; e.g.
         setting a default via ${jboss.server.log.threshold:WARN} will not work.         
       -->
      <param name="Threshold" value="${jboss.server.log.threshold}"/>

      <!-- Rollover at midnight each day -->
      <param name="DatePattern" value="'.'yyyy-MM-dd"/>

      <!-- Rollover at the top of each hour
      <param name="DatePattern" value="'.'yyyy-MM-dd-HH"/>
      -->

      <layout class="org.apache.log4j.PatternLayout">
         <!-- The default pattern: Date Priority [Category] (Thread) Message\n -->
         <param name="ConversionPattern" value="%d %-5p [%c] (%t) %m%n"/>

         <!-- The full pattern: Date MS Priority [Category] (Thread:NDC) Message\n
         <param name="ConversionPattern" value="%d %-5r %-5p [%c] (%t:%x) %m%n"/>
          -->
      </layout>
   </appender>

   <!-- A size based file rolling appender
   <appender name="FILE" class="org.jboss.logging.appender.RollingFileAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="File" value="${jboss.server.log.dir}/server.log"/>
     <param name="Append" value="false"/>
     <param name="MaxFileSize" value="500KB"/>
     <param name="MaxBackupIndex" value="1"/>

     <layout class="org.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="%d %-5p [%c] %m%n"/>
     </layout>	    
   </appender>
   -->

   <!-- ============================== -->
   <!-- Append messages to the console -->
   <!-- ============================== -->

   <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      <param name="Target" value="System.out"/>
      <param name="Threshold" value="INFO"/>

      <layout class="org.apache.log4j.PatternLayout">
         <!-- The default pattern: Date Priority [Category] Message\n -->
         <param name="ConversionPattern" value="%d{ABSOLUTE} %-5p [%c{1}] %m%n"/>
      </layout>
   </appender>

   <!-- ====================== -->
   <!-- More Appender examples -->
   <!-- ====================== -->

   <!-- Buffer events and log them asynchronously
   <appender name="ASYNC" class="org.apache.log4j.AsyncAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <appender-ref ref="FILE"/>
     <appender-ref ref="CONSOLE"/>
     <appender-ref ref="SMTP"/>
   </appender>
   -->

   <!-- EMail events to an administrator
   <appender name="SMTP" class="org.apache.log4j.net.SMTPAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="Threshold" value="ERROR"/>
     <param name="To" value="admin@myhost.domain.com"/>
     <param name="From" value="nobody@myhost.domain.com"/>
     <param name="Subject" value="JBoss Sever Errors"/>
     <param name="SMTPHost" value="localhost"/>
     <param name="BufferSize" value="10"/>
     <layout class="org.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="[%d{ABSOLUTE},%c{1}] %m%n"/>
     </layout>
   </appender>
   -->

   <!-- Syslog events
   <appender name="SYSLOG" class="org.apache.log4j.net.SyslogAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="Facility" value="LOCAL7"/>
     <param name="FacilityPrinting" value="true"/>
     <param name="SyslogHost" value="localhost"/>
     <layout class="org.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="[%d{ABSOLUTE},%c{1}] %m%n"/>
     </layout>
   </appender>
   -->

   <!-- Log events to JMS (requires a topic to be created)
   <appender name="JMS" class="org.apache.log4j.net.JMSAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="Threshold" value="ERROR"/>
     <param name="TopicConnectionFactoryBindingName" value="java:/ConnectionFactory"/>
     <param name="TopicBindingName" value="topic/MyErrorsTopic"/>
   </appender>
   -->

   <!-- Log events through SNMP
   <appender name="TRAP_LOG" class="org.apache.log4j.ext.SNMPTrapAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="ImplementationClassName" value="org.apache.log4j.ext.JoeSNMPTrapSender"/>
     <param name="ManagementHost" value="127.0.0.1"/>
     <param name="ManagementHostTrapListenPort" value="162"/>
     <param name="EnterpriseOID" value="1.3.6.1.4.1.24.0"/>
     <param name="LocalIPAddress" value="127.0.0.1"/>
     <param name="LocalTrapSendPort" value="161"/>
     <param name="GenericTrapType" value="6"/>
     <param name="SpecificTrapType" value="12345678"/>
     <param name="CommunityString" value="public"/>
     <param name="ForwardStackTraceWithTrap" value="true"/>
     <param name="Threshold" value="DEBUG"/>
     <param name="ApplicationTrapOID" value="1.3.6.1.4.1.24.12.10.22.64"/>
     <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d,%p,[%t],[%c],%m%n"/>
     </layout>
   </appender>
   -->

   <!--  Emit events as JMX notifications
   <appender name="JMX" class="org.jboss.monitor.services.JMXNotificationAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      
      <param name="Threshold" value="WARN"/>
      <param name="ObjectName" value="jboss.system:service=Logging,type=JMXNotificationAppender"/>
      
      <layout class="org.apache.log4j.PatternLayout">
         <param name="ConversionPattern" value="%d %-5p [%c] %m"/>
      </layout>
   </appender>
   -->

   <!-- Security AUDIT Appender
   <appender name="AUDIT" class="org.jboss.logging.appender.DailyRollingFileAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      <param name="File" value="${jboss.server.log.dir}/audit.log"/>
      <param name="Append" value="true"/>
      <param name="DatePattern" value="'.'yyyy-MM-dd"/>
      <layout class="org.apache.log4j.PatternLayout">
         <param name="ConversionPattern" value="%d %-5p [%c] (%t:%x) %m%n"/>
      </layout>
   </appender>
   -->
   
   <!-- ================ -->
   <!-- Limit categories -->
   <!-- ================ -->

   <!-- Limit the org.apache category to INFO as its DEBUG is verbose -->
   <category name="org.apache">
      <priority value="INFO"/>
   </category>
   
   <!-- Limit JSF logging to DEBUG.  FINER and FINEST will not be logged -->
   <category name="javax.enterprise.resource.webcontainer.jsf">
     <priority value="DEBUG" />
   </category>

   <!-- Limit the jacorb category to WARN as its INFO is verbose -->
   <category name="jacorb">
      <priority value="WARN"/>
   </category>
   
   <!-- Set the logging level of the JSF implementation -->
   <category name="javax.enterprise.resource.webcontainer.jsf">
     <priority value="INFO" />
   </category>
   
   <!-- Limit the org.jgroups category to WARN as its INFO is verbose -->
   <category name="org.jgroups">
      <priority value="WARN"/>
   </category>
   
   <!-- Limit the org.quartz category to INFO as its DEBUG is verbose -->
   <category name="org.quartz">
      <priority value="INFO"/>
   </category>
   
   <!-- Limit JBoss categories
   <category name="org.jboss">
      <priority value="INFO"/>
   </category>
   -->

   <!-- Limit the JSR77 categories -->
   <category name="org.jboss.management">
      <priority value="INFO"/>
   </category>

   <!-- Show the evolution of the DataSource pool in the logs [inUse/Available/Max]
   <category name="org.jboss.resource.connectionmanager.JBossManagedConnectionPool">
     <priority value="TRACE"/>
   </category>
   -->

   <!-- Category specifically for Security Audit Provider 
   <category name="org.jboss.security.audit.providers.LogAuditProvider" additivity="false">
     <priority value="TRACE"/>
     <appender-ref ref="AUDIT"/>
   </category>
   -->
   
   <!-- Limit the org.jboss.serial (jboss-serialization) to INFO as its DEBUG is verbose -->
   <category name="org.jboss.serial">
      <priority value="INFO"/>
   </category>
  
   <!-- Decrease the priority threshold for the org.jboss.varia category
   <category name="org.jboss.varia">
     <priority value="DEBUG"/>
   </category>
   -->
   
   <!-- Enable JBossWS message tracing
   <category name="org.jboss.ws.core.MessageTrace">
     <priority value="TRACE"/>
   </category>
   -->
   
   <!--
      | An example of enabling the custom TRACE level priority that is used
      | by the JBoss internals to diagnose low level details. This example
      | turns on TRACE level msgs for the org.jboss.ejb.plugins package and its
      | subpackages. This will produce A LOT of logging output.
      |
      | Note: since jboss AS 4.2.x, the trace level is supported natively by
      | log4j, so although the custom org.jboss.logging.XLevel priority will
      | still work, there is no need to use it. The two examples that follow
      | will both enable trace logging.
   <category name="org.jboss.system">
     <priority value="TRACE" class="org.jboss.logging.XLevel"/>
   </category>
   <category name="org.jboss.ejb.plugins">
     <priority value="TRACE"/>
   </category>
   -->
  
   <!--
       | Logs these events to SNMP:
           - server starts/stops
           - cluster evolution (node death/startup)
           - When an EJB archive is deployed (and associated verified messages)
           - When an EAR archive is deployed
      	 
   <category name="org.jboss.system.server.Server">
     <priority value="INFO" />
     <appender-ref ref="TRAP_LOG"/>
   </category>
  
   <category name="org.jboss.ha.framework.interfaces.HAPartition.lifecycle">
     <priority value="INFO" />
     <appender-ref ref="TRAP_LOG"/>
   </category>

   <category name="org.jboss.deployment.MainDeployer">
     <priority value="ERROR" />
     <appender-ref ref="TRAP_LOG"/>
   </category>
   
   <category name="org.jboss.ejb.EJBDeployer">
     <priority value="INFO" />
     <appender-ref ref="TRAP_LOG"/>
   </category>
   
   <category name="org.jboss.deployment.EARDeployer">
     <priority value="INFO" />
     <appender-ref ref="TRAP_LOG"/>
   </category>
   -->

   <!-- Clustering logging -->
   <!-- Uncomment the following to redirect the org.jgroups and
      org.jboss.ha categories to a cluster.log file.

   <appender name="CLUSTER" class="org.jboss.logging.appender.RollingFileAppender">
     <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
     <param name="File" value="${jboss.server.log.dir}/cluster.log"/>
     <param name="Append" value="false"/>
     <param name="MaxFileSize" value="500KB"/>
     <param name="MaxBackupIndex" value="1"/>

     <layout class="org.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="%d %-5p [%c] %m%n"/>
     </layout>
   </appender>
   <category name="org.jgroups">
     <priority value="DEBUG" />
     <appender-ref ref="CLUSTER"/>
   </category>
   <category name="org.jboss.ha">
     <priority value="DEBUG" />
     <appender-ref ref="CLUSTER"/>
   </category>
   -->
   
   <!-- ======================= -->
   <!-- Setup the Root category -->
   <!-- ======================= -->

   <root>
      <appender-ref ref="CONSOLE"/>
      <appender-ref ref="FILE"/>
   </root>

</log4j:configuration>

Se non ho capito male, la console è definita come appender ma come mai su eclipse non leggo nulla appena clicco su un link ad una pagina jsp che da errore?

Grazie a tutti, ciao ciao.