Log4j定時打印日誌及添加模塊名配置的Java代碼實例

配置間隔時間，定時打印日誌
接到個需求，通過log4j定時打印日誌，需求描述如下：需要能夠定時打印日誌，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: 每週
• '.'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類源碼並並改名MinuteRollingAppender，為了在log4j.xml中配置，增加配置項intervalTime並添加set、get方法；

 private int intervalTime = 10;

2）由於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；由於其方法就是根據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，服務於多種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"> <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>

關於定時實現，還可以採用java提供的Timer實現，也就免去了每次記錄日誌時計算並且比較時間，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）並發

並發問題可能發生的一個地方在run()中調用closeFile();後，正好subAppend()方法寫日誌，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) ..............................

使用Timer實現比較簡單，但是Timer裡面的任務如果執行時間太長，會獨占Timer對象，使得後面的任務無法幾時的執行，解決方法也比較簡單，採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> * 採用ScheduledExecutorService實現定時配置打印日誌* <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."); } } } }

關於定時的實現，差不多就到這裡了，採用的都默認是10分鐘產生一個新的日誌文件，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的日誌文件，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，唯一需要解決的是並發問題，即文件關閉rename文件時，發生了記錄日誌事件時，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誌文件中，不過希望能夠在日誌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，我們採用RollingFileAppender類為基類進行改造。

首先，添加配置項moduleName，並增加get、set方法；

由於繼承自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)); } }