Back to index...

	/*
	* Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/


	package java.util.logging;

	import java.io.*;
	import java.security.AccessController;
	import java.security.PrivilegedAction;
	import java.util.Objects;

	/**
	* Stream based logging {@code Handler}.
	* <p>
	* This is primarily intended as a base class or support class to
	* be used in implementing other logging {@code Handlers}.
	* <p>
	* {@code LogRecords} are published to a given {@code java.io.OutputStream}.
	* <p>
	* <b>Configuration:</b>
	* By default each {@code StreamHandler} is initialized using the following
	* {@code LogManager} configuration properties where {@code <handler-name>}
	* refers to the fully-qualified class name of the handler.
	* If properties are not defined
	* (or have invalid values) then the specified default values are used.
	* <ul>
	* <li> <handler-name>.level
	* specifies the default level for the {@code Handler}
	* (defaults to {@code Level.INFO}). </li>
	* <li> <handler-name>.filter
	* specifies the name of a {@code Filter} class to use
	* (defaults to no {@code Filter}). </li>
	* <li> <handler-name>.formatter
	* specifies the name of a {@code Formatter} class to use
	* (defaults to {@code java.util.logging.SimpleFormatter}). </li>
	* <li> <handler-name>.encoding
	* the name of the character set encoding to use (defaults to
	* the default platform encoding). </li>
	* </ul>
	* <p>
	* For example, the properties for {@code StreamHandler} would be:
	* <ul>
	* <li> java.util.logging.StreamHandler.level=INFO </li>
	* <li> java.util.logging.StreamHandler.formatter=java.util.logging.SimpleFormatter </li>
	* </ul>
	* <p>
	* For a custom handler, e.g. com.foo.MyHandler, the properties would be:
	* <ul>
	* <li> com.foo.MyHandler.level=INFO </li>
	* <li> com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li>
	* </ul>
	*
	* @since 1.4
	*/

	public class StreamHandler extends Handler {
	private OutputStream output;
	private boolean doneHeader;
	private volatile Writer writer;

	/**
	* Create a {@code StreamHandler}, with no current output stream.
	*/
	public StreamHandler() {
	// configure with specific defaults for StreamHandler
	super(Level.INFO, new SimpleFormatter(), null);
	}

	/**
	* Create a {@code StreamHandler} with a given {@code Formatter}
	* and output stream.
	*
	* @param out the target output stream
	* @param formatter Formatter to be used to format output
	*/
	public StreamHandler(OutputStream out, Formatter formatter) {
	// configure with default level but use specified formatter
	super(Level.INFO, null, Objects.requireNonNull(formatter));

	setOutputStreamPrivileged(out);
	}

	/**
	* @see Handler#Handler(Level, Formatter, Formatter)
	*/
	StreamHandler(Level defaultLevel,
	Formatter defaultFormatter,
	Formatter specifiedFormatter) {
	super(defaultLevel, defaultFormatter, specifiedFormatter);
	}

	/**
	* Change the output stream.
	* <P>
	* If there is a current output stream then the {@code Formatter}'s
	* tail string is written and the stream is flushed and closed.
	* Then the output stream is replaced with the new output stream.
	*
	* @param out New output stream. May not be null.
	* @throws SecurityException if a security manager exists and if
	* the caller does not have {@code LoggingPermission("control")}.
	*/
	protected synchronized void setOutputStream(OutputStream out) throws SecurityException {
	if (out == null) {
	throw new NullPointerException();
	}
	flushAndClose();
	output = out;
	doneHeader = false;
	String encoding = getEncoding();
	if (encoding == null) {
	writer = new OutputStreamWriter(output);
	} else {
	try {
	writer = new OutputStreamWriter(output, encoding);
	} catch (UnsupportedEncodingException ex) {
	// This shouldn't happen. The setEncoding method
	// should have validated that the encoding is OK.
	throw new Error("Unexpected exception " + ex);
	}
	}
	}

	/**
	* Set (or change) the character encoding used by this {@code Handler}.
	* <p>
	* The encoding should be set before any {@code LogRecords} are written
	* to the {@code Handler}.
	*
	* @param encoding The name of a supported character encoding.
	* May be null, to indicate the default platform encoding.
	* @throws SecurityException if a security manager exists and if
	* the caller does not have {@code LoggingPermission("control")}.
	* @throws UnsupportedEncodingException if the named encoding is
	* not supported.
	*/
	@Override
	public synchronized void setEncoding(String encoding)
	throws SecurityException, java.io.UnsupportedEncodingException {
	super.setEncoding(encoding);
	if (output == null) {
	return;
	}
	// Replace the current writer with a writer for the new encoding.
	flush();
	if (encoding == null) {
	writer = new OutputStreamWriter(output);
	} else {
	writer = new OutputStreamWriter(output, encoding);
	}
	}

	/**
	* Format and publish a {@code LogRecord}.
	* <p>
	* The {@code StreamHandler} first checks if there is an {@code OutputStream}
	* and if the given {@code LogRecord} has at least the required log level.
	* If not it silently returns. If so, it calls any associated
	* {@code Filter} to check if the record should be published. If so,
	* it calls its {@code Formatter} to format the record and then writes
	* the result to the current output stream.
	* <p>
	* If this is the first {@code LogRecord} to be written to a given
	* {@code OutputStream}, the {@code Formatter}'s "head" string is
	* written to the stream before the {@code LogRecord} is written.
	*
	* @param record description of the log event. A null record is
	* silently ignored and is not published
	*/
	@Override
	public synchronized void publish(LogRecord record) {
	if (!isLoggable(record)) {
	return;
	}
	String msg;
	try {
	msg = getFormatter().format(record);
	} catch (Exception ex) {
	// We don't want to throw an exception here, but we
	// report the exception to any registered ErrorManager.
	reportError(null, ex, ErrorManager.FORMAT_FAILURE);
	return;
	}

	try {
	if (!doneHeader) {
	writer.write(getFormatter().getHead(this));
	doneHeader = true;
	}
	writer.write(msg);
	} catch (Exception ex) {
	// We don't want to throw an exception here, but we
	// report the exception to any registered ErrorManager.
	reportError(null, ex, ErrorManager.WRITE_FAILURE);
	}
	}


	/**
	* Check if this {@code Handler} would actually log a given {@code LogRecord}.
	* <p>
	* This method checks if the {@code LogRecord} has an appropriate level and
	* whether it satisfies any {@code Filter}. It will also return false if
	* no output stream has been assigned yet or the LogRecord is null.
	*
	* @param record a {@code LogRecord} (may be null).
	* @return true if the {@code LogRecord} would be logged.
	*
	*/
	@Override
	public boolean isLoggable(LogRecord record) {
	if (writer == null \|\| record == null) {
	return false;
	}
	return super.isLoggable(record);
	}

	/**
	* Flush any buffered messages.
	*/
	@Override
	public synchronized void flush() {
	if (writer != null) {
	try {
	writer.flush();
	} catch (Exception ex) {
	// We don't want to throw an exception here, but we
	// report the exception to any registered ErrorManager.
	reportError(null, ex, ErrorManager.FLUSH_FAILURE);
	}
	}
	}

	private synchronized void flushAndClose() throws SecurityException {
	checkPermission();
	if (writer != null) {
	try {
	if (!doneHeader) {
	writer.write(getFormatter().getHead(this));
	doneHeader = true;
	}
	writer.write(getFormatter().getTail(this));
	writer.flush();
	writer.close();
	} catch (Exception ex) {
	// We don't want to throw an exception here, but we
	// report the exception to any registered ErrorManager.
	reportError(null, ex, ErrorManager.CLOSE_FAILURE);
	}
	writer = null;
	output = null;
	}
	}

	/**
	* Close the current output stream.
	* <p>
	* The {@code Formatter}'s "tail" string is written to the stream before it
	* is closed. In addition, if the {@code Formatter}'s "head" string has not
	* yet been written to the stream, it will be written before the
	* "tail" string.
	*
	* @throws SecurityException if a security manager exists and if
	* the caller does not have LoggingPermission("control").
	*/
	@Override
	public synchronized void close() throws SecurityException {
	flushAndClose();
	}

	// Package-private support for setting OutputStream
	// with elevated privilege.
	@SuppressWarnings("removal")
	final void setOutputStreamPrivileged(final OutputStream out) {
	AccessController.doPrivileged(new PrivilegedAction<Void>() {
	@Override
	public Void run() {
	setOutputStream(out);
	return null;
	}
	}, null, LogManager.controlPermission);
	}
	}

Back to index...