Flex日誌管理

用過java的日誌架構log4j之後，你就會被它方便而又強大的功能所吸引。我們不僅可以控制日誌輸出的目的地，還可以控制日至輸出層級，便於調試和發布。
    其實在Flex

中也提供了這樣的一個架構，Logging API就是最基本的日誌控制架構，只不過大部分的人都在用最簡單的trace()函數罷了。
    Logging API不僅提供了最基本的trace功能，還提供了log target，也就是輸出的方式。還提供了destination目的地的配置功能。通過我們對log的層級控制我們可以輸
出一些普通訊息而過濾掉debug的資訊。除此之外還可以進行自訂log target，對架構進行擴充。

重要概念和類介紹：

Logger
： 提供了介面發送log到一個特定的target，它實現了ILogger介面。
Log target
：定義了日誌將會被寫道哪裡。Flex

提供了兩類target，TraceTarget和MiniDebugTarget。TraceTarget就是將log輸出到trace()函數輸出的檔案中，也就是flashlog.txt檔案中。當然你也可以自訂一個log target。
Logging Level
：定義了當前系統可輸出的記錄層級。

如下表所示，按照高到低排列。如果現在的level是ALL，那麼系統中所有的日誌都會被輸出。如果是INFO，那麼高於INFO的DEBUG資訊就不會被輸出。這個很容易理解。

 

Logging level constant (int)	Description
ALL (0)	Designates that messages of all logging levels should be logged.
DEBUG (2)	Logs internal Flex activities. This is most useful when debugging anapplication.Select the DEBUG logging level to include DEBUG, INFO, WARN, ERROR, and FATAL messages in your log files.
INFO (4)	Logs general information.Select the INFO logging level to include INFO, WARN, ERROR, and FATAL messages in your log files.
WARN (6)	Logs a message when the application encounters a problem. These problems do not cause the application to stop running, but could lead to further errors.Select the WARN logging level to include WARN, ERROR, and FATAL messages in your log files.
ERROR(8)	Logs a message when a critical service is not available or a situation has occurred that restricts the use of the application. Select the ERROR logging level to include ERROR and FATAL messages in your log files.
FATAL (1000)	Logs a message when an event occurs that results in the failure of the application. Select the FATAL logging level to include only FATAL messages in your log files.

log target 過濾filters

logTarget.filters=["mx.rpc.*","mx.messaging.*"];


這個例子中就是指定了我們要輸出日誌的類和包。只有在mx.rpc和mx.messaging包下的類才能輸出log，忽略其他的。也可以是mxml形式：

<mx:TraceTarget id="logTarget" includeDate="true" includeTime="true"
                  includeCategory="true" includeLevel="true">
            <mx:filters>
                  <mx:Array>
                        <mx:String>mx.rpc.*</mx:String>
                        <mx:String>mx.messaging.*</mx:String>
                  </mx:Array>
            </mx:filters>
           <!-- 0 is represents the LogEventLevel.ALL constant. -->
           <mx:level>0</mx:level>
</mx:TraceTarget>

參數介紹
includeDate="true",輸出的log帶日期
includeTime="true", 輸出的log帶時間
includeCategory="true",輸出的log帶分類資訊，也就是哪個類或者控制項輸出的log
includeLevel="true"，輸出的log是否帶level資訊，如[INFO],[DEBUG]等。

來個實用的小例子

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml

" layout="absolute" initialize="initLog()">
 <mx:Script>
  <![CDATA[
   import mx.logging.*;
   import mx.logging.targets.*;
   private var myLogger : ILogger;
   public function printLog(level:Number):void
   {
    if(level ==2)
     myLogger.debug("This is debug click");
    if(level == 4)
     myLogger.info("This is info click");
    if(level == 6)
     myLogger.warn("This is warn click");
    if(level == 8)
     myLogger.error("This is error click");
    if(level ==1000)
     myLogger.fatal("This is fatal click");
   }
   private function initLog():void{
    /*
    // Create a target.
    var logTarget:TraceTarget = new TraceTarget();
    // Log only messages for the classes in the mx.rpc.* and
    // mx.messaging packages.
    logTarget.filters=["*"];
    // Log all log levels.
    logTarget.level = LogEventLevel.ALL;
    // Add date, time, category, and log level to the output.
    logTarget.includeDate = true;
    logTarget.includeTime = true;
    logTarget.includeCategory = true;
    logTarget.includeLevel = true;
    // Begin logging.
    Log.addTarget(logTarget);
    */
    myLogger = Log.getLogger("myCustomClass");
   }
  ]]>
 </mx:Script>
 <mx:TraceTarget level="4" includeDate="true" includeTime="true"
  includeCategory="true" includeLevel="true">
  <mx:filters>
   <mx:Array>
    <mx:String>*</mx:String>
   </mx:Array>
  </mx:filters>
 </mx:TraceTarget>
 <mx:VBox width="100%" height="100%" horizontalAlign="center" verticalAlign="middle">
  <mx:Button label="DEBUG(2)" click="printLog(2)"/>
  <mx:Button label="INFO(4)" click="printLog(4)"/>
  <mx:Button label="WARN(6)" click="printLog(6)"/>
  <mx:Button label="ERROR(8)" click="printLog(8)"/>
  <mx:Button label="FATAL(1000)" click="printLog(1000)"/>

 </mx:VBox>
 
</mx:Application>

 

本文轉自：http://www.javaeye.com/topic/392808