Log4J: Jak mogę przekierować OutputStream lub Writer do pisarz (y) loggera?

Question

Mam metodę, która działa asynchronicznie po uruchomieniu, przy użyciu OutputStream lub Writer jako parametr.

Działa jako adapter nagrywania dla OutputStream lub Writer (to jest API innej firmy, którego nie można zmienić).

Jak mogę przekazać wewnętrzną metodę OutputStream lub Writer Log4J do tej metody?
... ponieważ Log4J połknęła System.out i System.err, którego używałem wcześniej.

Answer 1

Moja sugestia jest, dlaczego nie piszesz OutputStream ?! Już miałem napisać dla ciebie, ale znalazłem ten dobry przykład w sieci, sprawdź to!

LogOutputStream.java

/* 
* Jacareto Copyright (c) 2002-2005 
* Applied Computer Science Research Group, Darmstadt University of 
* Technology, Institute of Mathematics & Computer Science, 
* Ludwigsburg University of Education, and Computer Based 
* Learning Research Group, Aachen University. All rights reserved. 
* 
* Jacareto is free software; you can redistribute it and/or 
* modify it under the terms of the GNU General Public 
* License as published by the Free Software Foundation; either 
* version 2 of the License, or (at your option) any later version. 
* 
* Jacareto is distributed in the hope that it will be useful, 
* but WITHOUT ANY WARRANTY; without even the implied warranty of 
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
* General Public License for more details. 
* 
* You should have received a copy of the GNU General Public 
* License along with Jacareto; if not, write to the Free 
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
* 
*/ 

package jacareto.toolkit.log4j; 


import org.apache.log4j.Level; 
import org.apache.log4j.Logger; 

import java.io.OutputStream; 

/** 
* This class logs all bytes written to it as output stream with a specified logging level. 
* 
* @author <a href="mailto:cspannagel@web.de">Christian Spannagel</a> 
* @version 1.0 
*/ 
public class LogOutputStream extends OutputStream { 
    /** The logger where to log the written bytes. */ 
    private Logger logger; 

    /** The level. */ 
    private Level level; 

    /** The internal memory for the written bytes. */ 
    private String mem; 

    /** 
    * Creates a new log output stream which logs bytes to the specified logger with the specified 
    * level. 
    * 
    * @param logger the logger where to log the written bytes 
    * @param level the level 
    */ 
    public LogOutputStream (Logger logger, Level level) { 
     setLogger (logger); 
     setLevel (level); 
     mem = ""; 
    } 

    /** 
    * Sets the logger where to log the bytes. 
    * 
    * @param logger the logger 
    */ 
    public void setLogger (Logger logger) { 
     this.logger = logger; 
    } 

    /** 
    * Returns the logger. 
    * 
    * @return DOCUMENT ME! 
    */ 
    public Logger getLogger() { 
     return logger; 
    } 

    /** 
    * Sets the logging level. 
    * 
    * @param level DOCUMENT ME! 
    */ 
    public void setLevel (Level level) { 
     this.level = level; 
    } 

    /** 
    * Returns the logging level. 
    * 
    * @return DOCUMENT ME! 
    */ 
    public Level getLevel() { 
     return level; 
    } 

    /** 
    * Writes a byte to the output stream. This method flushes automatically at the end of a line. 
    * 
    * @param b DOCUMENT ME! 
    */ 
    public void write (int b) { 
     byte[] bytes = new byte[1]; 
     bytes[0] = (byte) (b & 0xff); 
     mem = mem + new String(bytes); 

     if (mem.endsWith ("\n")) { 
      mem = mem.substring (0, mem.length() - 1); 
      flush(); 
     } 
    } 

    /** 
    * Flushes the output stream. 
    */ 
    public void flush() { 
     logger.log (level, mem); 
     mem = ""; 
    } 
} 

Answer 2

Źródło: http://sysgears.com/articles/how-to-redirect-stdout-and-stderr-writing-to-a-log4j-appender/

Blockquote

Log4j nie pozwala złapać wiadomości stdout i stderr po wyjęciu z pudełka. Jeśli jednak korzystasz z komponentów innych firm i musisz rejestrować komunikaty, które przepływają do strumieni, możesz zrobić małą sztuczkę i zaimplementować niestandardowy strumień wyjściowy, który obsługuje rejestrowanie.

Zostało to już zrobione przez Jima Moore'a (patrz LoggingOutputStream w kodzie źródłowym log4j). Jedynym problemem jest to, że LoggingOutputStream JimMoore wymaga org.apache.log4j.Category i org.apache.log4j.Priority, które są teraz częściowo nieaktualne.

Tutaj jest modyfikowany LoggingOutputStream że unika metod nieaktualne:

public class LoggingOutputStream extends OutputStream { 

    /** 
    * Default number of bytes in the buffer. 
    */ 
    private static final int DEFAULT_BUFFER_LENGTH = 2048; 

    /** 
    * Indicates stream state. 
    */ 
    private boolean hasBeenClosed = false; 

    /** 
    * Internal buffer where data is stored. 
    */ 
    private byte[] buf; 

    /** 
    * The number of valid bytes in the buffer. 
    */ 
    private int count; 

    /** 
    * Remembers the size of the buffer. 
    */ 
    private int curBufLength; 

    /** 
    * The logger to write to. 
    */ 
    private Logger log; 

    /** 
    * The log level. 
    */ 
    private Level level; 

    /** 
    * Creates the Logging instance to flush to the given logger. 
    * 
    * @param log   the Logger to write to 
    * @param level  the log level 
    * @throws IllegalArgumentException in case if one of arguments 
    *         is null. 
    */ 
    public LoggingOutputStream(final Logger log, 
           final Level level) 
      throws IllegalArgumentException { 
     if (log == null || level == null) { 
      throw new IllegalArgumentException(
        "Logger or log level must be not null"); 
     } 
     this.log = log; 
     this.level = level; 
     curBufLength = DEFAULT_BUFFER_LENGTH; 
     buf = new byte[curBufLength]; 
     count = 0; 
    } 

    /** 
    * Writes the specified byte to this output stream. 
    * 
    * @param b the byte to write 
    * @throws IOException if an I/O error occurs. 
    */ 
    public void write(final int b) throws IOException { 
     if (hasBeenClosed) { 
      throw new IOException("The stream has been closed."); 
     } 
     // don't log nulls 
     if (b == 0) { 
      return; 
     } 
     // would this be writing past the buffer? 
     if (count == curBufLength) { 
      // grow the buffer 
      final int newBufLength = curBufLength + 
        DEFAULT_BUFFER_LENGTH; 
      final byte[] newBuf = new byte[newBufLength]; 
      System.arraycopy(buf, 0, newBuf, 0, curBufLength); 
      buf = newBuf; 
      curBufLength = newBufLength; 
     } 

     buf[count] = (byte) b; 
     count++; 
    } 

    /** 
    * Flushes this output stream and forces any buffered output 
    * bytes to be written out. 
    */ 
    public void flush() { 
     if (count == 0) { 
      return; 
     } 
     final byte[] bytes = new byte[count]; 
     System.arraycopy(buf, 0, bytes, 0, count); 
     String str = new String(bytes); 
     log.log(level, str); 
     count = 0; 
    } 

    /** 
    * Closes this output stream and releases any system resources 
    * associated with this stream. 
    */ 
    public void close() { 
     flush(); 
     hasBeenClosed = true; 
    } 
} 

Teraz można złapać wiadomości, które są wypłukiwane do stderr lub stdout w następujący sposób:

System.setErr(new PrintStream(new LoggingOutputStream(
     Logger.getLogger("outLog"), Level.ERROR))); 

konfiguracji log4j.properties:

log4j.logger.outLog=error, out_log 

log4j.appender.out_log=org.apache.log4j.RollingFileAppender 
log4j.appender.out_log.file=/logs/error.log 
log4j.appender.out_log.MaxFileSize=10MB 
log4j.appender.out_log.threshold=error 

Dmitriy Pavlenko, SysGears

Blockquote

Answer 3

Ponieważ poprzedni przykład Writer, że skierowane do LOG4J zgasł: http://www.opensource.apple.com/source/JBoss/JBoss-737/jboss-all/common/src/main/org/jboss/logging/util/LoggerWriter.java