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
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'.'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
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));
}
}
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