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  1. package test.log
  2. import java.io.*;
  3. import java.nio.charset.CharsetEncoder;
  4. import java.nio.charset.StandardCharsets;
  5. import java.time.Instant;
  6. import java.time.ZoneId;
  7. import java.time.format.DateTimeFormatter;
  8. import java.util.Locale;
  9. import java.util.Random;
  10. import java.util.concurrent.Semaphore;
  11.  
  12. public class Logger {
  13.     public static final DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("MMM dd, yyyy hh:mm:ss a").withZone(ZoneId.systemDefault());
  14.     private final String fileName = "log4j.log";
  15.     public final String dirName;
  16.     private final long maxFileSizeBytes;
  17.     private Level minLevel;
  18.     private final int maxBackups;
  19.     private final File file;
  20.     private CountingWriter w;
  21.     private boolean stdoutMode;
  22.  
  23.     private static Logger logger;
  24.     public static void setLogger(Logger logger){
  25.         Logger.logger=logger;
  26.     }
  27.     public static Logger getLogger(String name) {
  28.         if(logger==null) logger=new Logger();
  29.         return logger;
  30.     }
  31.  
  32.     public enum Level{debug(),info(),warn(),error(),fatal();
  33.         private final String nameUcase;
  34.         Level() {
  35.             this.nameUcase = this.name().toUpperCase(Locale.ROOT);
  36.         }
  37.     }
  38.  
  39.     public Logger(long maxFileSizeBytes, Level minLevel, String dirName, boolean stdoutMode, int maxBackups) {
  40.         this.maxFileSizeBytes = maxFileSizeBytes;
  41.         this.minLevel = minLevel;
  42.         this.dirName=dirName;
  43.         this.stdoutMode = stdoutMode;
  44.         this.file=new File(dirName,fileName);
  45.         this.maxBackups = maxBackups;
  46.         System.out.println("file= " + this.file);
  47.         this.w=initFileWriter();
  48.     }
  49.  
  50.     private Logger() {
  51.         this(1024*1024*20L,Level.info,"/var/log",false, 10);
  52.     }
  53.  
  54.  
  55.     private CountingWriter initFileWriter() {
  56.         try {
  57.             final long length ;
  58.             final boolean exists = file.exists();
  59.             if (exists) {
  60.                 length = file.length();
  61.             }
  62.             else {
  63.                 final File parentFile = file.getParentFile();
  64.                 parentFile.mkdirs();
  65.                 length=0;
  66.             }
  67.             CharsetEncoder encoder = StandardCharsets.UTF_8.newEncoder();
  68.             FileOutputStream outputStream=new FileOutputStream(file,exists);
  69.             final CountingWriter countingWriter = new CountingWriter(new BufferedWriter(new OutputStreamWriter(outputStream, encoder)), length);
  70.             stdoutMode=false;
  71.             return countingWriter;
  72.         } catch (Exception e) {
  73.             System.err.println("error initialising logging! Setting 'stdout' mode");
  74.             e.printStackTrace();
  75.             stdoutMode=true;
  76.         }
  77.         return null;
  78.     }
  79.     public void flush() {
  80.         try {
  81.             w.flush();
  82.         } catch (IOException e) {
  83.             e.printStackTrace();
  84.         }
  85.     }
  86.  
  87.     private void log(Level level, String message, Throwable e){
  88.         if(message==null && e==null) return;
  89.         if(level.ordinal()<minLevel.ordinal()) return;
  90.         try {
  91.             if(stdoutMode){
  92.                 writeToStdErr(message,e,null,null);
  93.                 return;
  94.             }
  95.             if(rollLock.availablePermits()<1){
  96.                 writeToStdErr(message, e, "rolling", null);
  97.                 return;
  98.             }
  99.             w.write(dateFormatter.format(Instant.now()));
  100.             w.write(' ');
  101.             w.write(level.nameUcase);
  102.             w.write(' ');
  103.             w.write('[');
  104.             w.write(Thread.currentThread().getName());
  105.             w.write(']');
  106.             w.write(' ');
  107.             final boolean hasMessage = message != null;
  108.             if(hasMessage){
  109.                 w.write(message);
  110.             }
  111.             if(e!=null){
  112.                 if(hasMessage) w.write(' ');
  113.                 final PrintWriter pw = new PrintWriter(w, false);
  114.                 e.printStackTrace(pw);
  115.             }
  116.             w.write('\n');
  117.             if(level.ordinal()>= Level.warn.ordinal() || isDebugEnabled()) w.flush();
  118.             //flush immediately (e.g. in example of fatal error
  119.             //also flush immediately if debugging: since we don't care so much about perf if we're debugging
  120.             if(w.getCountBytes()>=maxFileSizeBytes){
  121.                 if(rollLock.tryAcquire()){//if someone's already on it, just give up
  122.                     try {
  123.                         roll();
  124.                     } finally {
  125.                         rollLock.release();
  126.                     }
  127.                 }
  128.             }
  129.  
  130.         } catch (Exception e1) { //last thing we want is logging causing issues
  131.             writeToStdErr(message, e, "exception encountered", e1);
  132.         }
  133.  
  134.     }
  135.  
  136.     private void writeToStdErr(String message, Throwable e, String reasonCannotWriteToFile, Exception reasonError) {
  137.         if (reasonCannotWriteToFile!=null){
  138.             System.err.print("[");
  139.             System.err.print(reasonCannotWriteToFile);
  140.             System.err.print("] ");
  141.         }
  142.         if (reasonError!=null){
  143.             System.err.print("[");
  144.             reasonError.printStackTrace();
  145.             System.err.print("] ");
  146.         }
  147.         if (message!=null) System.err.println(message);
  148.         if (e!=null) e.printStackTrace();
  149.     }
  150.  
  151.     private final Semaphore rollLock = new Semaphore(1);
  152.     private void roll() {
  153.         System.out.println("LOGGER::: roll thread=" + Thread.currentThread().getName() + " t=" + System.currentTimeMillis());
  154.         renameOldBackupFiles();
  155.         final File newestBackup = backupFile(1);
  156.         try {
  157.             w.close();
  158.         } catch (IOException e) {
  159.             e.printStackTrace();
  160.         }
  161.         //rename the main log file to newest backup (which we just renamed)
  162.         boolean success = file.renameTo(newestBackup);
  163.         System.out.println("LOGGER::: rename " + file + " to=" + newestBackup + " success=" + success);
  164.         this.w=initFileWriter();//should now be writing to file (which is empty)
  165.     }
  166.  
  167.     private void renameOldBackupFiles() {
  168.         File oldestBackup = backupFile(maxBackups);
  169.         if (oldestBackup.exists()) {
  170.             boolean deleted = oldestBackup.delete();
  171.             System.out.println("LOGGER::: delete " + oldestBackup + " success=" + deleted);
  172.         }
  173. //               - rename all other backup files <5 in desc order (so log.4 -> log.5 and so on)
  174.         for (int backup = maxBackups-1; backup > 0; backup--) {
  175.             final File backupFile = backupFile(backup);
  176.             if (!backupFile.exists()) continue;
  177.             final File destFile = backupFile(backup + 1);
  178.             boolean success = backupFile.renameTo(destFile);
  179.             System.out.println("LOGGER::: rename " + backupFile + " to=" + destFile + " success=" + success);
  180.         }
  181.     }
  182.  
  183.     private File backupFile(int backupNumber) {
  184.         return new File(dirName,String.format("%s.%s",fileName, backupNumber));
  185.     }
  186.  
  187.  
  188.     private static class CountingWriter extends Writer{
  189.         private final Writer writer;
  190.         private long countBytes;
  191.         public CountingWriter(Writer w, long initialCount) {
  192.             this.writer = w;
  193.             countBytes=initialCount;
  194.         }
  195.         public void write(char[] cbuf, int off, int len) throws IOException {
  196.             writer.write(cbuf,off,len);
  197.             final long wrote = (len - off);
  198.             countBytes += wrote;//this will likely be wrong if we use extended chars which take two bytes? ascii-type chars take 1 byte, but some take 2. But probably doesn't matter, unless we start logging korean strings or something?
  199.         }
  200.         public void flush() throws IOException { writer.flush(); }
  201.         public void close() throws IOException { writer.close(); }
  202.  
  203.         public long getCountBytes() { return countBytes; }
  204.     }
  205.  
  206.     //log4j api
  207.     public void debug(String format) {debug(format,null); }
  208.     public void debug(Throwable e) {debug(null,e); }
  209.     public void debug(String format, Throwable e) {log(Level.debug,format,e); }
  210.  
  211.     public void info(String format) {info(format,null); }
  212.     public void info(Throwable e) {info(null,e); }
  213.     public void info(String format, Throwable e) {log(Level.info,format,e); }
  214.  
  215.     public void warn(String format) {warn(format,null);}
  216.     public void warn(Throwable e) {warn(null,e); }
  217.     public void warn(String format, Throwable e) {log(Level.warn,format,e); }
  218.  
  219.     public void error(String format) {error(format,null); }
  220.     public void error(Throwable e) { error(null,e);}
  221.     public void error(String format, Throwable e) {log(Level.error,format,e); }
  222.  
  223.     public void fatal(String format) {fatal(format,null); }
  224.     public void fatal(Throwable e) {fatal(null,e); }
  225.     public void fatal(String format, Throwable e) {
  226.         log(Level.fatal,format,e);
  227.     }
  228.  
  229.     //new api meths
  230.     public void warnf(String format, Throwable e, Object... paramters) {warn(String.format(format, (Object[]) paramters),e);}
  231.     public void infof(String format, Throwable e, Object... paramters) {info(String.format(format, (Object[]) paramters),e);}
  232.     public void debugf(String format, Throwable e, Object... paramters) {debug(String.format(format, (Object[]) paramters),e);}
  233.  
  234.  
  235.     public boolean isDebugEnabled() {
  236.         return minLevel.ordinal()<=Level.debug.ordinal();
  237.     }
  238.  
  239. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
Main.java:11: error: class Logger is public, should be declared in a file named Logger.java
public class Logger {
       ^
1 error
stdout 
Standard output is empty
https://ideone.com/XKg5M9
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
secret

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