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" class="net.csdn.blog.MinuteRollingAppender">
  <param name="File" value="log4jTest.log" />
  <param name="Append" value="true" />
  <param name="intervalTime" value="2"/>
  <layout class="org.apache.log4j.PatternLayout">
   <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)
..............................

解决方法比较简单，直接让整个run()方法为同步的，加上synchronized关键字即可；不过目前楼主没有解决如果真要写，而且写的速度够快的情况下可能丢失日志的情况；
   2）性能

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));
 }
}