Log4j定时打印日志及添加模块名配置的Java代码实例

配置间隔时间，定时打印日志
接到个需求，通过log4j定时打印日志，需求描述如下：需要能够定时打印日志，时间间隔可配。说到定时，首先想到了DailyRollingFileAppender类，各种定时，根据datePattern，这个可以参考类SimpleDateFormat类，常见的一些定时设置如下：

• '.'yyyy-MM: 每月
• '.'yyyy-ww: 每周
• '.'yyyy-MM-dd: 每天
• '.'yyyy-MM-dd-a: 每天两次
• '.'yyyy-MM-dd-HH: 每小时
• '.'yyyy-MM-dd-HH-mm: 每分钟

通过观察发现没有n分钟类似的日期格式，因此，在DailyRollingFileAppender类基础上进行自定义类的编写。过程如下：

1）拷贝DailyRollingFileAppender类源码并并改名MinuteRollingAppender，为了在log4j.xml中配置，增加配置项intervalTime并添加set、get方法；

private int intervalTime = 10; 

2）由于DailyRollingFileAppender类使用了RollingCalendar类来计算下一次间隔时间，而需要传递参数intervalTime，因此修改RollingCalendar类为内部类；由于其方法就是根据datePattern来计算下一次rollOver动作的时间，此时不需要其他的时间模式，修改方法如下：

public Date getNextCheckDate(Date now) {  this.setTime(now);  this.set(Calendar.SECOND, 0);  this.set(Calendar.MILLISECOND, 0);  this.add(Calendar.MINUTE, intervalTime);  return getTime(); } 

3）按照分钟可配时，时间模式就需要禁用了，将其改为static final，响应的去掉其get、set方法和MinuteRollingAppender构造函数中的datePattern参数

private static String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'"; 

同样，服务于多种datePattern的方法computeCheckPeriod()也可以删除； 至此改造就完成了，成品类如下：

package net.csdn.blog;  import java.io.File; import java.io.IOException; import java.io.InterruptedIOException; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; import java.util.GregorianCalendar;  import org.apache.log4j.FileAppender; import org.apache.log4j.Layout; import org.apache.log4j.helpers.LogLog; import org.apache.log4j.spi.LoggingEvent;  /**  * 按分钟可配置定时appender  *  * @author coder_xia  *  */ public class MinuteRollingAppender extends FileAppender {  /**   * The date pattern. By default, the pattern is set to "'.'yyyy-MM-dd"   * meaning daily rollover.   */  private static String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'";  /**   * 间隔时间，单位：分钟   */  private int intervalTime = 10;   /**   * The log file will be renamed to the value of the scheduledFilename   * variable when the next interval is entered. For example, if the rollover   * period is one hour, the log file will be renamed to the value of   * "scheduledFilename" at the beginning of the next hour.   *   * The precise time when a rollover occurs depends on logging activity.   */  private String scheduledFilename;   /**   * The next time we estimate a rollover should occur.   */  private long nextCheck = System.currentTimeMillis() - 1;   Date now = new Date();   SimpleDateFormat sdf;   RollingCalendar rc = new RollingCalendar();   /**   * The default constructor does nothing.   */  public MinuteRollingAppender()  {  }   /**   * Instantiate a <code>MinuteRollingAppender</code> and open the file   * designated by <code>filename</code>. The opened filename will become the   * ouput destination for this appender.   */  public MinuteRollingAppender(Layout layout, String filename)    throws IOException  {   super(layout, filename, true);   activateOptions();  }   /**   * @return the intervalTime   */  public int getIntervalTime()  {   return intervalTime;  }   /**   * @param intervalTime   *   the intervalTime to set   */  public void setIntervalTime(int intervalTime)  {   this.intervalTime = intervalTime;  }   @Override  public void activateOptions()  {   super.activateOptions();   if (fileName != null)   {    now.setTime(System.currentTimeMillis());    sdf = new SimpleDateFormat(DATEPATTERN);    File file = new File(fileName);    scheduledFilename = fileName      + sdf.format(new Date(file.lastModified()));    }   else   {    LogLog      .error("Either File or DatePattern options are not set for appender ["        + name + "].");   }  }   /**   * Rollover the current file to a new file.   */  void rollOver() throws IOException  {   String datedFilename = fileName + sdf.format(now);   // It is too early to roll over because we are still within the   // bounds of the current interval. Rollover will occur once the   // next interval is reached.   if (scheduledFilename.equals(datedFilename))   {    return;   }    // close current file, and rename it to datedFilename   this.closeFile();    File target = new File(scheduledFilename);   if (target.exists())   {    target.delete();   }    File file = new File(fileName);   boolean result = file.renameTo(target);   if (result)   {    LogLog.debug(fileName + " -> " + scheduledFilename);   }   else   {    LogLog.error("Failed to rename [" + fileName + "] to ["      + scheduledFilename + "].");   }    try   {    // This will also close the file. This is OK since multiple    // close operations are safe.    this.setFile(fileName, true, this.bufferedIO, this.bufferSize);   }   catch (IOException e)   {    errorHandler.error("setFile(" + fileName + ", true) call failed.");   }   scheduledFilename = datedFilename;  }   /**   * This method differentiates MinuteRollingAppender from its super class.   *   * <p>   * Before actually logging, this method will check whether it is time to do   * a rollover. If it is, it will schedule the next rollover time and then   * rollover.   * */  @Override  protected void subAppend(LoggingEvent event)  {   long n = System.currentTimeMillis();   if (n >= nextCheck)   {    now.setTime(n);    nextCheck = rc.getNextCheckMillis(now);    try    {     rollOver();    }    catch (IOException ioe)    {     if (ioe instanceof InterruptedIOException)     {      Thread.currentThread().interrupt();     }     LogLog.error("rollOver() failed.", ioe);    }   }   super.subAppend(event);  }   /**   * RollingCalendar is a helper class to MinuteRollingAppender. Given a   * periodicity type and the current time, it computes the start of the next   * interval.   * */  class RollingCalendar extends GregorianCalendar  {   private static final long serialVersionUID = -3560331770601814177L;    RollingCalendar()   {    super();   }    public long getNextCheckMillis(Date now)   {    return getNextCheckDate(now).getTime();   }    public Date getNextCheckDate(Date now)   {    this.setTime(now);    this.set(Calendar.SECOND, 0);    this.set(Calendar.MILLISECOND, 0);    this.add(Calendar.MINUTE, intervalTime);    return getTime();   }  } } 

测试配置文件如下：

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">  <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">   <appender name="myFile">    <param name="File" value="log4jTest.log" />   <param name="Append" value="true" />   <param name="intervalTime" value="2"/>   <layout>    <param name="ConversionPattern" value="%p %d (%c:%L)- %m%n" />   </layout>  </appender>   <root>   <priority value="debug"/>   <appender-ref ref="myFile"/>   </root>  </log4j:configuration> 

关于定时实现，还可以采用java提供的Timer实现，也就免去了每次记录日志时计算并且比较时间，区别其实就是自己起个线程与调用rollOver方法，实现如下：

package net.csdn.blog;  import java.io.File; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Timer; import java.util.TimerTask;  import org.apache.log4j.FileAppender; import org.apache.log4j.Layout; import org.apache.log4j.helpers.LogLog;  public class TimerTaskRollingAppender extends FileAppender {  /**   * The date pattern. By default, the pattern is set to "'.'yyyy-MM-dd"   * meaning daily rollover.   */  private static final String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'";   /**   * 间隔时间，单位：分钟   */  private int intervalTime = 10;   SimpleDateFormat sdf = new SimpleDateFormat(DATEPATTERN);   /**   * The default constructor does nothing.   */  public TimerTaskRollingAppender()  {  }   /**   * Instantiate a <code>TimerTaskRollingAppender</code> and open the file   * designated by <code>filename</code>. The opened filename will become the   * ouput destination for this appender.   */  public TimerTaskRollingAppender(Layout layout, String filename)    throws IOException  {   super(layout, filename, true);   activateOptions();  }   /**   * @return the intervalTime   */  public int getIntervalTime()  {   return intervalTime;  }   /**   * @param intervalTime   *   the intervalTime to set   */  public void setIntervalTime(int intervalTime)  {   this.intervalTime = intervalTime;  }   @Override  public void activateOptions()  {   super.activateOptions();   Timer timer = new Timer();   timer.schedule(new LogTimerTask(), 1000, intervalTime * 60000);  }   class LogTimerTask extends TimerTask  {   @Override   public void run()   {    String datedFilename = fileName + sdf.format(new Date());    closeFile();    File target = new File(datedFilename);    if (target.exists())     target.delete();    File file = new File(fileName);    boolean result = file.renameTo(target);    if (result)     LogLog.debug(fileName + " -> " + datedFilename);    else     LogLog.error("Failed to rename [" + fileName + "] to ["       + datedFilename + "].");    try    {     setFile(fileName, true, bufferedIO, bufferSize);    }    catch (IOException e)    {     errorHandler.error("setFile(" + fileName       + ", true) call failed.");    }   }  } } 

不过，以上实现，存在2个问题：

1）并发

并发问题可能发生的一个地方在run()中调用closeFile();后，正好subAppend()方法写日志，此刻文件已关闭，则会报以下错误：

java.io.IOException: Stream closed  at sun.nio.cs.StreamEncoder.ensureOpen(Unknown Source)  at sun.nio.cs.StreamEncoder.write(Unknown Source)  at sun.nio.cs.StreamEncoder.write(Unknown Source)  at java.io.OutputStreamWriter.write(Unknown Source)  at java.io.Writer.write(Unknown Source) .............................. 

使用Timer实现比较简单，但是Timer里面的任务如果执行时间太长，会独占Timer对象，使得后面的任务无法几时的执行，解决方法也比较简单，采用线程池版定时器类ScheduledExecutorService，实现如下：

/**  *  */ package net.csdn.blog;  import java.io.File; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit;  import org.apache.log4j.FileAppender; import org.apache.log4j.Layout; import org.apache.log4j.helpers.LogLog;  /**  * @author coder_xia  *   <p>  *   采用ScheduledExecutorService实现定时配置打印日志  *   <p>  *  */ public class ScheduledExecutorServiceAppender extends FileAppender {  /**   * The date pattern. By default, the pattern is set to "'.'yyyy-MM-dd"   * meaning daily rollover.   */  private static final String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'";   /**   * 间隔时间，单位：分钟   */  private int intervalTime = 10;   SimpleDateFormat sdf = new SimpleDateFormat(DATEPATTERN);   /**   * The default constructor does nothing.   */  public ScheduledExecutorServiceAppender()  {  }   /**   * Instantiate a <code>ScheduledExecutorServiceAppender</code> and open the   * file designated by <code>filename</code>. The opened filename will become   * the ouput destination for this appender.   */  public ScheduledExecutorServiceAppender(Layout layout, String filename)    throws IOException  {   super(layout, filename, true);   activateOptions();  }   /**   * @return the intervalTime   */  public int getIntervalTime()  {   return intervalTime;  }   /**   * @param intervalTime   *   the intervalTime to set   */  public void setIntervalTime(int intervalTime)  {   this.intervalTime = intervalTime;  }   @Override  public void activateOptions()  {   super.activateOptions();   Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(     new LogTimerTask(), 1, intervalTime * 60000,     TimeUnit.MILLISECONDS);  }   class LogTimerTask implements Runnable  {   @Override   public void run()   {    String datedFilename = fileName + sdf.format(new Date());    closeFile();    File target = new File(datedFilename);    if (target.exists())     target.delete();    File file = new File(fileName);    boolean result = file.renameTo(target);    if (result)     LogLog.debug(fileName + " -> " + datedFilename);    else     LogLog.error("Failed to rename [" + fileName + "] to ["       + datedFilename + "].");    try    {     setFile(fileName, true, bufferedIO, bufferSize);    }    catch (IOException e)    {     errorHandler.error("setFile(" + fileName       + ", true) call failed.");    }   }  } } 

关于定时的实现，差不多就到这里了，采用的都默认是10分钟产生一个新的日志文件，在配置时可以自行设置，不过存在的一个隐患，万一配置的人不知道时间间隔是分钟，如果以为是秒，配了个600，又开了debug，产生上G的日志文件，这肯定是个灾难，下面的改造就是结合RollingFileAppender的最大大小和最多备份文件个数可配，再次进行完善，下次继续描述改造过程。

添加模块名配置
在前面讲到了log4j定时打印的定制类实现，就不讲指定大小和指定备份文件个数了，从RollingFileAppender类copy代码到前面的定制类中添加即可，唯一需要解决的是并发问题，即文件关闭rename文件时，发生了记录日志事件时，会报output stream closed的错误。

现在有这样一种应用场景，而且经常有：

1.项目包含有多个不同的工程；

2.同一工程包含不同的模块。

对第一种情况，可以通过配置log4j<catogery=“Test”>，再在产生Logger时使用类似如下方式：

Logger logger=Logger.getLogger("Test"); 

对第二种情况，我们希望能够将不同模块打印到同一个日志文件中，不过希望能够在日志中打印出模块名以便出问题时定位问题，因此便有了本文需要的在Appender类中添加配置ModuleName，下面开始改造，与定时打印不同，我们采用RollingFileAppender类为基类进行改造。

首先，添加配置项moduleName，并增加get、set方法；

由于继承自RollingFileAppender，所以只需要在subAppend()中格式化LoggingEvent中的数据，添加formatInfo方法格式化数据，代码略；

最终的成品类如下：

package net.csdn.blog;  import org.apache.log4j.Category; import org.apache.log4j.RollingFileAppender; import org.apache.log4j.spi.LoggingEvent;  /**  * @author coder_xia  *  */ public class ModuleAppender extends RollingFileAppender {  private String moduleName;   /**   * @return the moduleName   */  public String getModuleName()  {   return moduleName;  }   /**   * @param moduleName   *   the moduleName to set   */  public void setModuleName(String moduleName)  {   this.moduleName = moduleName;  }   /**   * 格式化打印内容   *   * @param event   *   event   * @return msg   */  private String formatInfo(LoggingEvent event)  {   StringBuilder sb = new StringBuilder();   if (moduleName != null)   {    sb.append(moduleName).append("|");    sb.append(event.getMessage());   }   return sb.toString();  }   @Override  public void subAppend(LoggingEvent event)  {   String msg = formatInfo(event);   super.subAppend(new LoggingEvent(Category.class.getName(), event     .getLogger(), event.getLevel(), msg, null));  } }