If you have the ability to do what Dave suggested, then that's the way to
go. If you really do need redirection (because of writing that happens in
classes you don't control, for example), then you need to use a
LoggingOutputStream. (I've submitted it as a contribution, but it hasn't
been added to CVS yet that I've seen, so I've included it below. This one
fixes a couple of minor bugs from the version I posted a month or so ago.)
Enjoy.
-Jim Moore
======
import java.io.*;
import org.apache.log4j.*;
/**
* An OutputStream that flushes out to a Category.<p>
*
* Note that no data is written out to the Category until the stream is
* flushed or closed.<p>
*
* Example:<pre>
* // make sure everything sent to System.err is logged
* System.setErr(new PrintStream(new LoggingOutputStream(Category.getRoot(),
Priority.WARN), true));
*
* // make sure everything sent to System.out is also logged
* System.setOut(new PrintStream(new LoggingOutputStream(Category.getRoot(),
Priority.INFO), true));
* </pre>
*
* @author <a href="mailto:[EMAIL PROTECTED]">Jim Moore</a>
* @see Category
*/
public class LoggingOutputStream extends OutputStream {
/**
* Used to maintain the contract of {@link #close()}.
*/
protected boolean hasBeenClosed = false;
/**
* The internal buffer where data is stored.
*/
protected byte[] buf;
/**
* The number of valid bytes in the buffer. This value is always
* in the range <tt>0</tt> through <tt>buf.length</tt>; elements
* <tt>buf[0]</tt> through <tt>buf[count-1]</tt> contain valid
* byte data.
*/
protected int count;
/**
* Remembers the size of the buffer for speed.
*/
private int bufLength;
/**
* The default number of bytes in the buffer. =2048
*/
public static final int DEFAULT_BUFFER_LENGTH = 2048;
/**
* The category to write to.
*/
protected Category category;
/**
* The priority to use when writing to the Category.
*/
protected Priority priority;
private LoggingOutputStream() {
// illegal
}
/**
* Creates the LoggingOutputStream to flush to the given Category.
*
* @param cat the Category to write to
*
* @param priority the Priority to use when writing to the Category
*
* @exception IllegalArgumentException
* if cat == null or priority == null
*/
public LoggingOutputStream(Category cat, Priority priority)
throws IllegalArgumentException {
if (cat == null) {
throw new IllegalArgumentException("cat == null");
}
if (priority == null) {
throw new IllegalArgumentException("priority == null");
}
this.priority = priority;
category = cat;
bufLength = DEFAULT_BUFFER_LENGTH;
buf = new byte[DEFAULT_BUFFER_LENGTH];
count = 0;
}
/**
* Closes this output stream and releases any system resources
* associated with this stream. The general contract of
<code>close</code>
* is that it closes the output stream. A closed stream cannot perform
* output operations and cannot be reopened.
*/
public void close() {
flush();
hasBeenClosed = true;
}
/**
* Writes the specified byte to this output stream. The general
* contract for <code>write</code> is that one byte is written
* to the output stream. The byte to be written is the eight
* low-order bits of the argument <code>b</code>. The 24
* high-order bits of <code>b</code> are ignored.
*
* @param b the <code>byte</code> to write
*
* @exception IOException
* if an I/O error occurs. In particular,
* an <code>IOException</code> may be thrown if the
* output stream has been closed.
*/
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 == bufLength) {
// grow the buffer
final int newBufLength = bufLength+DEFAULT_BUFFER_LENGTH;
final byte[] newBuf = new byte[newBufLength];
System.arraycopy(buf, 0, newBuf, 0, bufLength);
buf = newBuf;
bufLength = newBufLength;
}
buf[count] = (byte)b;
count++;
}
/**
* Flushes this output stream and forces any buffered output bytes
* to be written out. The general contract of <code>flush</code> is
* that calling it is an indication that, if any bytes previously
* written have been buffered by the implementation of the output
* stream, such bytes should immediately be written to their
* intended destination.
*/
public void flush() {
if (count == 0) {
return;
}
// don't print out blank lines; flushing from PrintStream puts out these
if (count == 1 && ((char)buf[0]) == '\n') {
reset();
return;
}
final byte[] theBytes = new byte[count];
System.arraycopy(buf, 0, theBytes, 0, count);
category.log(priority, new String(theBytes));
reset();
}
private void reset() {
// not resetting the buffer -- assuming that if it grew that it
// will likely grow similarly again
count = 0;
}
}
-----Original Message-----
From: Dave King [mailto:[EMAIL PROTECTED]]
Sent: Monday, March 26, 2001 4:07 PM
To: 'LOG4J Users Mailing List'
Subject: RE: Logging stack trace
In the javadocs for org.apache.log4j.Category
warn(Object message, Throwable t)
Log a message with the WARN priority including the stack trace of the
Throwable t passed as parameter.
there are of course version of this method for error, info and debug.
-Peace
Dave
> -----Original Message-----
> From: Loda, Joe [mailto:[EMAIL PROTECTED]]
> Sent: Monday, March 26, 2001 2:01 PM
> To: '[EMAIL PROTECTED]'
> Subject: Logging stack trace
>
>
> Hi,
>
> How can I redirect the stack trace from an exception:
>
> try
> {
> ... stuff ...
> }
> catch ( Exception e )
> {
> e.printStackTrace(); // divert to log4j
> }
>
> Thanks in advance,
> Joe
>
> ---
> Joe Loda, mpct Solutions Corporation, Chicago
> [EMAIL PROTECTED]
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