Java code example of Log4j regularly printing logs and adding module name configuration

Configure interval time, print logs regularly
I received a requirement to print logs regularly through log4j. The requirement is described as follows: logs need to be printed regularly, and the time interval is configurable. Speaking of timing, the first thing that comes to mind is the DailyRollingFileAppender class. Various timings. According to datePattern, this can refer to the SimpleDateFormat class. Some common timing settings are as follows:

'.'yyyy-MM: Monthly

'.'yyyy-ww: weekly

'.'yyyy-MM-dd: daily

'.'yyyy-MM-dd-a: twice a day

'.'yyyy-MM-dd-HH: every hour

'.'yyyy-MM-dd-HH-mm: every minute

Through observation, it is found that there are no similar n minutes date format, therefore, write a custom class based on the DailyRollingFileAppender class. The process is as follows:

1) Copy the DailyRollingFileAppender class source code and rename it MinuteRollingAppender. In order to configure it in log4j.xml, add the configuration item intervalTime and add set and get methods;

private int intervalTime = 10;

2) Since the DailyRollingFileAppender class uses the RollingCalendar class to calculate the next interval time, and needs to pass the parameter intervalTime, the RollingCalendar class is modified as an internal class; since its method is to calculate the time of the next rollOver action based on datePattern, there is no need to If you need other time modes, the modification method is as follows:

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) If the time can be configured according to minutes, the time mode needs to be disabled, change it to static final, and remove its get accordingly , the datePattern parameter in the set method and the MinuteRollingAppender constructor

private static String DATEPATTERN = "'.'yyyy-MM-dd-HH-mm'.log'";

Similarly, the method computeCheckPeriod() that serves multiple datePatterns can also be deleted; At this point, the transformation is complete, and the finished class is as follows:

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 MinuteRollingAppender and open the file
  * designated by filename. 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.
  *
  * 

  * 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();
  }
 }
}

The test configuration file is as follows:

<?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>

Regarding timing implementation, you can also use the Timer implementation provided by java. This eliminates the need to calculate and compare the time each time the log is recorded. The difference is actually starting a thread yourself and calling the rollOver method. The implementation is as follows:

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.");
   }
  }
 }
}

However, there are 2 problems with the above implementation. Questions:

1) Concurrency

One place where concurrency problems may occur is after calling closeFile(); in run(), the subAppend() method happens to write the log, and the file is closed at this moment. The following error will be reported:

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)
..............................

The solution is relatively simple, just make the entire run() method synchronous and add the synchronized keyword; however, the poster has not yet solved the problem. To write, and the writing speed is fast enough, the log may be lost;
2) Performance

It is relatively simple to use Timer to implement, but if the execution time of the task in Timer is too long, it will monopolize Timer object, making it impossible to execute subsequent tasks. The solution is relatively simple. Use the thread pool version of the timer class ScheduledExecutorService, which is implemented as follows:

/**
 *
 */
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 "&#39;.&#39;yyyy-MM-dd"
  * meaning daily rollover.
  */
 private static final String DATEPATTERN = "&#39;.&#39;yyyy-MM-dd-HH-mm&#39;.log&#39;";
  
 /**
  * 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.");
   }
  }
 }
}

About the implementation of timing, that’s almost it. The default is to generate a new log file every 10 minutes. You can set it yourself during configuration. However, there is a hidden danger in case the person who configures does not know that the time interval is minutes. , if you think it is seconds, allocate 600, turn on debug, and generate a log file of GB, this is definitely a disaster. The following modification is to combine the maximum size of RollingFileAppender and the maximum number of backup files that can be configured, and improve it again. The description of the transformation process will continue next time.

Add module name configuration
I talked about the custom class implementation of log4j scheduled printing earlier. I will not talk about specifying the size and the number of backup files. I copy the code from the RollingFileAppender class and add it to the previous custom class. That’s it. The only thing that needs to be solved is the concurrency problem, that is, when the file is closed and the rename file is closed, and a log event occurs, an output stream closed error will be reported.

Now there is such an application scenario, and it often happens:

1. The project contains multiple different projects;

2. The same project contains different modules.

For the first case, you can configure log4j, and then use a method similar to the following when generating Logger:

Logger logger=Logger.getLogger("Test");

For the second case In the two cases, we hope to be able to print different modules to the same log file, but we hope to be able to print the module name in the log so that we can locate the problem when there is a problem. Therefore, we need to add the configuration ModuleName to the Appender class as needed in this article. Let's start the transformation. Different from scheduled printing, we use the RollingFileAppender class as the base class for transformation.

First, add the configuration item moduleName, and add get and set methods;

Since it is inherited from RollingFileAppender, you only need to format the data in LoggingEvent in subAppend() and add the formatInfo method format Transformed data, the code is omitted;

The final product category is as follows:

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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