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)); 
 } 
}