/* MemoryHandler.java -- a class for buffering log messages in a memory buffer
Copyright (C) 2002, 2004 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.
GNU Classpath is distributed in the hope that it will be useful, but
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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02111-1307 USA.
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making a combined work based on this library. Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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package java.util.logging;
/**
* A <code>MemoryHandler</code> maintains a circular buffer of
* log records.
*
* <p><strong>Configuration:</strong> Values of the subsequent
* <code>LogManager</code> properties are taken into consideration
* when a <code>MemoryHandler</code> is initialized.
* If a property is not defined, or if it has an invalid
* value, a default is taken without an exception being thrown.
*
* <ul>
* <li><code>java.util.MemoryHandler.level</code> - specifies
* the initial severity level threshold. Default value:
* <code>Level.ALL</code>.</li>
* <li><code>java.util.MemoryHandler.filter</code> - specifies
* the name of a Filter class. Default value: No Filter.</li>
* <li><code>java.util.MemoryHandler.size</code> - specifies the
* maximum number of log records that are kept in the circular
* buffer. Default value: 1000.</li>
* <li><code>java.util.MemoryHandler.push</code> - specifies the
* <code>pushLevel</code>. Default value:
* <code>Level.SEVERE</code>.</li>
* <li><code>java.util.MemoryHandler.target</code> - specifies the
* name of a subclass of {@link Handler} that will be used as the
* target handler. There is no default value for this property;
* if it is not set, the no-argument MemoryHandler constructor
* will throw an exception.</li>
* </ul>
*
* @author Sascha Brawer (brawer@acm.org)
*/
public class MemoryHandler
extends Handler
{
/**
* The storage area used for buffering the unpushed log records in
* memory.
*/
private final LogRecord[] buffer;
/**
* The current position in the circular buffer. For a new
* MemoryHandler, or immediately after {@link #push()} was called,
* the value of this variable is zero. Each call to {@link
* #publish(LogRecord)} will store the published LogRecord into
* <code>buffer[position]</code> before position is incremented by
* one. If position becomes greater than the size of the buffer, it
* is reset to zero.
*/
private int position;
/**
* The number of log records which have been published, but not
* pushed yet to the target handler.
*/
private int numPublished;
/**
* The push level threshold for this <code>Handler</code>. When a
* record is published whose severity level is greater than or equal
* to the <code>pushLevel</code> of this <code>MemoryHandler</code>,
* the {@link #push()} method will be invoked for pushing the buffer
* contents to the target <code>Handler</code>.
*/
private Level pushLevel;
/**
* The Handler to which log records are forwarded for actual
* publication.
*/
private final Handler target;
/**
* Constructs a <code>MemoryHandler</code> for keeping a circular
* buffer of LogRecords; the initial configuration is determined by
* the <code>LogManager</code> properties described above.
*/
public MemoryHandler()
{
this((Handler) LogManager.getInstanceProperty(
"java.util.logging.MemoryHandler.target",
Handler.class, /* default */ null),
LogManager.getIntPropertyClamped(
"java.util.logging.MemoryHandler.size",
/* default */ 1000,
/* minimum value */ 1,
/* maximum value */ Integer.MAX_VALUE),
LogManager.getLevelProperty(
"java.util.logging.MemoryHandler.push",
/* default push level */ Level.SEVERE));
}
/**
* Constructs a <code>MemoryHandler</code> for keeping a circular
* buffer of LogRecords, given some parameters. The values of the
* other parameters are taken from LogManager properties, as
* described above.
*
* @param target the target handler that will receive those
* log records that are passed on for publication.
*
* @param size the number of log records that are kept in the buffer.
* The value must be a at least one.
*
* @param pushLevel the push level threshold for this
* <code>MemoryHandler</code>. When a record is published whose
* severity level is greater than or equal to
* <code>pushLevel</code>, the {@link #push()} method will be
* invoked in order to push the bufffer contents to
* <code>target</code>.
*
* @throws java.lang.IllegalArgumentException if <code>size</code>
* is negative or zero. The GNU implementation also throws
* an IllegalArgumentException if <code>target</code> or
* <code>pushLevel</code> are <code>null</code>, but the
* API specification does not prescribe what should happen
* in those cases.
*/
public MemoryHandler(Handler target, int size, Level pushLevel)
{
if ((target == null) || (size <= 0) || (pushLevel == null))
throw new IllegalArgumentException();
buffer = new LogRecord[size];
this.pushLevel = pushLevel;
this.target = target;
setLevel(LogManager.getLevelProperty(
"java.util.logging.MemoryHandler.level",
/* default value */ Level.ALL));
setFilter((Filter) LogManager.getInstanceProperty(
"java.util.logging.MemoryHandler.filter",
/* must be instance of */ Filter.class,
/* default value */ null));
}
/**
* Stores a <code>LogRecord</code> in a fixed-size circular buffer,
* provided the record passes all tests for being loggable. If the
* buffer is full, the oldest record will be discarded.
*
* <p>If the record has a severity level which is greater than or
* equal to the <code>pushLevel</code> of this
* <code>MemoryHandler</code>, the {@link #push()} method will be
* invoked for pushing the buffer contents to the target
* <code>Handler</code>.
*
* <p>Most applications do not need to call this method directly.
* Instead, they will use use a {@link Logger}, which will create
* LogRecords and distribute them to registered handlers.
*
* @param record the log event to be published.
*/
public void publish(LogRecord record)
{
if (!isLoggable(record))
return;
buffer[position] = record;
position = (position + 1) % buffer.length;
numPublished = numPublished + 1;
if (record.getLevel().intValue() >= pushLevel.intValue())
push();
}
/**
* Pushes the contents of the memory buffer to the target
* <code>Handler</code> and clears the buffer. Note that
* the target handler will discard those records that do
* not satisfy its own severity level threshold, or that are
* not considered loggable by an installed {@link Filter}.
*
* <p>In case of an I/O failure, the {@link ErrorManager} of the
* target <code>Handler</code> will be notified, but the caller of
* this method will not receive an exception.
*/
public void push()
{
int i;
if (numPublished < buffer.length)
{
for (i = 0; i < position; i++)
target.publish(buffer[i]);
}
else
{
for (i = position; i < buffer.length; i++)
target.publish(buffer[i]);
for (i = 0; i < position; i++)
target.publish(buffer[i]);
}
numPublished = 0;
position = 0;
}
/**
* Forces any data that may have been buffered by the target
* <code>Handler</code> to the underlying output device, but
* does <em>not</em> push the contents of the circular memory
* buffer to the target handler.
*
* <p>In case of an I/O failure, the {@link ErrorManager} of the
* target <code>Handler</code> will be notified, but the caller of
* this method will not receive an exception.
*
* @see #push()
*/
public void flush()
{
target.flush();
}
/**
* Closes this <code>MemoryHandler</code> and its associated target
* handler, discarding the contents of the memory buffer. However,
* any data that may have been buffered by the target
* <code>Handler</code> is forced to the underlying output device.
*
* <p>As soon as <code>close</code> has been called,
* a <code>Handler</code> should not be used anymore. Attempts
* to publish log records, to flush buffers, or to modify the
* <code>Handler</code> in any other way may throw runtime
* exceptions after calling <code>close</code>.</p>
*
* <p>In case of an I/O failure, the <code>ErrorManager</code> of
* the associated target <code>Handler</code> will be informed, but
* the caller of this method will not receive an exception.</p>
*
* @throws SecurityException if a security manager exists and
* the caller is not granted the permission to control
* the logging infrastructure.
*
* @see #push()
*/
public void close()
throws SecurityException
{
push();
/* This will check for LoggingPermission("control"). If the
* current security context does not grant this permission,
* push() has been executed, but this does not impose a
* security risk.
*/
target.close();
}
/**
* Returns the push level threshold for this <code>Handler</code>.
* When a record is published whose severity level is greater
* than or equal to the <code>pushLevel</code> of this
* <code>MemoryHandler</code>, the {@link #push()} method will be
* invoked for pushing the buffer contents to the target
* <code>Handler</code>.
*
* @return the push level threshold for automatic pushing.
*/
public Level getPushLevel()
{
return pushLevel;
}
/**
* Sets the push level threshold for this <code>Handler</code>.
* When a record is published whose severity level is greater
* than or equal to the <code>pushLevel</code> of this
* <code>MemoryHandler</code>, the {@link #push()} method will be
* invoked for pushing the buffer contents to the target
* <code>Handler</code>.
*
* @param pushLevel the push level threshold for automatic pushing.
*
* @exception SecurityException if a security manager exists and
* the caller is not granted the permission to control
* the logging infrastructure.
*
* @exception NullPointerException if <code>pushLevel</code> is
* <code>null</code>.
*/
public void setPushLevel(Level pushLevel)
{
LogManager.getLogManager().checkAccess();
/* Throws a NullPointerException if pushLevel is null. */
pushLevel.getClass();
this.pushLevel = pushLevel;
}
}