配置間隔時間，定時打印日志
接到個需求，通過log4j定時打印日志，需求描述如下：需要能夠定時打印日志，時間間隔可配。說到定時，首先想到了DailyRollingFileAppender類，各種定時，根據datePattern，這個可以參考類SimpleDateFormat類，常見的一些定時設置如下：
- '.'yyyy-MM: 每月
- '.'yyyy-ww: 每周
- '.'yyyy-MM-dd: 每天
- '.'yyyy-MM-dd-a: 每天兩次
- '.'yyyy-MM-dd-HH: 每小時
- '.'yyyy-MM-dd-HH-mm: 每分鐘
通過觀察發現沒有n分鐘類似的日期格式，因此，在DailyRollingFileAppender類基礎上進行自定義類的編寫。過程如下：
1）拷貝DailyRollingFileAppender類源碼并并改名MinuteRollingAppender，為了在log4j.xml中配置，增加配置項intervalTime并添加set、get方法；
private int intervalTime = 10;
2）由于DailyRollingFileAppender類使用了RollingCalendar類來計算下一次間隔時間，而需要傳遞參數intervalTime，因此修改RollingCalendar類為內部類；由于其方法就是根據datePattern來計算下一次rollOver動作的時間，此時不需要其他的時間模式，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）按照分鐘可配時，時間模式就需要禁用了，將其改為static final，響應的去掉其get、set方法和MinuteRollingAppender構造函數中的datePattern參數
private static String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'";
同樣，服務于多種datePattern的方法computeCheckPeriod()也可以刪除； 至此改造就完成了，成品類如下：
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;
/**
* 按分鐘可配置定時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'";
/**
* 間隔時間，單位：分鐘
*/
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();
}
}
}
測試配置文件如下：
<?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>
關于定時實現，還可以采用java提供的Timer實現，也就免去了每次記錄日志時計算并且比較時間，區別其實就是自己起個線程與調用rollOver方法，實現如下：
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'";
/**
* 間隔時間，單位：分鐘
*/
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.");
}
}
}
}
不過，以上實現，存在2個問題：
1）并發
并發問題可能發生的一個地方在run()中調用closeFile();后，正好subAppend()方法寫日志，此刻文件已關閉，則會報以下錯誤：
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) ..............................
解決方法比較簡單，直接讓整個run()方法為同步的，加上synchronized關鍵字即可；不過目前樓主沒有解決如果真要寫，而且寫的速度夠快的情況下可能丟失日志的情況；
2）性能
2）性能
使用Timer實現比較簡單，但是Timer里面的任務如果執行時間太長，會獨占Timer對象，使得后面的任務無法幾時的執行，解決方法也比較簡單，采用線程池版定時器類ScheduledExecutorService，實現如下：
/**
*
*/
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實現定時配置打印日志
* <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'";
/**
* 間隔時間，單位：分鐘
*/
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.");
}
}
}
}
關于定時的實現，差不多就到這里了，采用的都默認是10分鐘產生一個新的日志文件，在配置時可以自行設置，不過存在的一個隱患，萬一配置的人不知道時間間隔是分鐘，如果以為是秒，配了個600，又開了debug，產生上G的日志文件，這肯定是個災難，下面的改造就是結合RollingFileAppender的最大大小和最多備份文件個數可配，再次進行完善，下次繼續描述改造過程。
添加模塊名配置
在前面講到了log4j定時打印的定制類實現，就不講指定大小和指定備份文件個數了，從RollingFileAppender類copy代碼到前面的定制類中添加即可，唯一需要解決的是并發問題，即文件關閉rename文件時，發生了記錄日志事件時，會報output stream closed的錯誤。
現在有這樣一種應用場景，而且經常有：
1.項目包含有多個不同的工程；
2.同一工程包含不同的模塊。
對第一種情況，可以通過配置log4j<catogery=“Test”>，再在產生Logger時使用類似如下方式：
Logger logger=Logger.getLogger("Test");
對第二種情況，我們希望能夠將不同模塊打印到同一個日志文件中，不過希望能夠在日志中打印出模塊名以便出問題時定位問題，因此便有了本文需要的在Appender類中添加配置ModuleName，下面開始改造，與定時打印不同，我們采用RollingFileAppender類為基類進行改造。
首先，添加配置項moduleName，并增加get、set方法；
由于繼承自RollingFileAppender，所以只需要在subAppend()中格式化LoggingEvent中的數據，添加formatInfo方法格式化數據，代碼略；
最終的成品類如下：
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;
}
/**
* 格式化打印內容
*
* @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));
}
}
