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Log4J: ¿Cómo redirecciono un OutputStream o Writer a los escritores del registrador?

Question

Tengo un método que se ejecuta de forma asíncrona después del inicio, utilizando OutputStream o Writer como parámetro.

Actúa como un adaptador de grabación para un OutputStream o Writer ( es una API de terceros que no puedo cambiar ).

¿Cómo podría pasar el OutputStream o Writer interno de Log4J a ese método?
... porque Log4J traga System.out y System.err, estaba usando antes.

Answer 1

Desde el ejemplo anterior de un escritor que se dirigió a Log4J murió: http://www.opensource.apple.com/source/JBoss/JBoss-737/jboss-all/common/src/main/org/jboss/logging/util/LoggerWriter.java

Answer 2

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

Blockquote

Log4j no permite capturar mensajes de stdout y stderr fuera de la caja. Sin embargo, si está utilizando componentes de terceros y tiene que registrar los mensajes que descargan en las secuencias, puede hacer un pequeño truco e implementar una secuencia de salida personalizada que admita el registro.

Esto ya lo hizo Jim Moore (consulte LoggingOutputStream en el código fuente de log4j). El único problema es que el LoggingOutputStream de JimMoore requiere org.apache.log4j.Category y org.apache.log4j.Priority que ahora están parcialmente en desuso.

Aquí se modifica LoggingOutputStream que evita los métodos en desuso:

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;
}
}

Ahora puede capturar los mensajes que se descargan a stderr o stdout de la siguiente manera:

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

La configuración de 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

Mi sugerencia es, ¿por qué no escribes tu OutputStream entonces? Estaba a punto de escribir uno para ti, pero encontré este buen ejemplo en la red, ¡échale un vistazo!

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:[email protected]">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 4

Puedes usar Log4j IOStreams

El componente IOStreams es una extensión de la API Log4j que proporciona numerosas clases de java.io que pueden escribir en un registrador mientras se escribe en otro OutputStream o Writer, o los contenidos leídos por InputStream o Reader pueden ser escuchados por un registrador.

Puedes crear un OutputStream de esta manera:

OutputStream outputStream = IoBuilder
.forLogger(logger)
.buildOutputStream();

A continuación se muestra un ejemplo con Appium, que se inicia programáticamente y controla su registro con log4j.

 final Logger logger = LogManager.getLogger(getClass());
cap = new DesiredCapabilities();
cap.setCapability("noReset", "false");
//Build the Appium service
builder = new AppiumServiceBuilder();
builder.withIPAddress("127.0.0.1");
builder.usingPort(4723);
builder.withCapabilities(cap);
builder.withArgument(GeneralServerFlag.SESSION_OVERRIDE);
builder.withArgument(GeneralServerFlag.LOG_LEVEL,"debug");
//Start the server with the builder
service = AppiumDriverLocalService.buildService(builder);
OutputStream outputStream = IoBuilder
.forLogger(logger)
.buildOutputStream();
service.addOutPutStream(outputStream);
service.start();

¡¡¡Espero que esto ayude!!!