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/*
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* Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util.logging;
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/**
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* <tt>Handler</tt> that buffers requests in a circular buffer in memory.
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* <p>
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* Normally this <tt>Handler</tt> simply stores incoming <tt>LogRecords</tt>
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* into its memory buffer and discards earlier records. This buffering
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* is very cheap and avoids formatting costs. On certain trigger
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* conditions, the <tt>MemoryHandler</tt> will push out its current buffer
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* contents to a target <tt>Handler</tt>, which will typically publish
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* them to the outside world.
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* <p>
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* There are three main models for triggering a push of the buffer:
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* <ul>
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* <li>
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* An incoming <tt>LogRecord</tt> has a type that is greater than
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* a pre-defined level, the <tt>pushLevel</tt>.
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* <li>
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* An external class calls the <tt>push</tt> method explicitly.
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* <li>
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* A subclass overrides the <tt>log</tt> method and scans each incoming
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* <tt>LogRecord</tt> and calls <tt>push</tt> if a record matches some
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* desired criteria.
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* </ul>
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* <p>
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* <b>Configuration:</b>
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* By default each <tt>MemoryHandler</tt> is initialized using the following
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* LogManager configuration properties. If properties are not defined
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* (or have invalid values) then the specified default values are used.
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* If no default value is defined then a RuntimeException is thrown.
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* <ul>
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* <li> java.util.logging.MemoryHandler.level
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* specifies the level for the <tt>Handler</tt>
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* (defaults to <tt>Level.ALL</tt>).
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* <li> java.util.logging.MemoryHandler.filter
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* specifies the name of a <tt>Filter</tt> class to use
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* (defaults to no <tt>Filter</tt>).
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* <li> java.util.logging.MemoryHandler.size
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* defines the buffer size (defaults to 1000).
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* <li> java.util.logging.MemoryHandler.push
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* defines the <tt>pushLevel</tt> (defaults to <tt>level.SEVERE</tt>).
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* <li> java.util.logging.MemoryHandler.target
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* specifies the name of the target <tt>Handler </tt> class.
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* (no default).
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* </ul>
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*
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* @since 1.4
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*/
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public class MemoryHandler extends Handler {
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private final static int DEFAULT_SIZE = 1000;
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private Level pushLevel;
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private int size;
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private Handler target;
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private LogRecord buffer[];
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int start, count;
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// Private method to configure a ConsoleHandler from LogManager
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// properties and/or default values as specified in the class
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// javadoc.
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private void configure() {
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LogManager manager = LogManager.getLogManager();
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String cname = getClass().getName();
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pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE);
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size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE);
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if (size <= 0) {
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size = DEFAULT_SIZE;
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}
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setLevel(manager.getLevelProperty(cname +".level", Level.ALL));
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setFilter(manager.getFilterProperty(cname +".filter", null));
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setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter()));
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}
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/**
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* Create a <tt>MemoryHandler</tt> and configure it based on
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* <tt>LogManager</tt> configuration properties.
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*/
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public MemoryHandler() {
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sealed = false;
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configure();
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sealed = true;
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String name = "???";
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try {
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LogManager manager = LogManager.getLogManager();
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name = manager.getProperty("java.util.logging.MemoryHandler.target");
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Class clz = ClassLoader.getSystemClassLoader().loadClass(name);
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target = (Handler) clz.newInstance();
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} catch (Exception ex) {
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throw new RuntimeException("MemoryHandler can't load handler \"" + name + "\"" , ex);
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}
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init();
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}
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// Initialize. Size is a count of LogRecords.
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private void init() {
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buffer = new LogRecord[size];
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start = 0;
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count = 0;
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}
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/**
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* Create a <tt>MemoryHandler</tt>.
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* <p>
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* The <tt>MemoryHandler</tt> is configured based on <tt>LogManager</tt>
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* properties (or their default values) except that the given <tt>pushLevel</tt>
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* argument and buffer size argument are used.
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*
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* @param target the Handler to which to publish output.
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* @param size the number of log records to buffer (must be greater than zero)
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* @param pushLevel message level to push on
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*
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* @throws IllegalArgumentException if size is <= 0
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*/
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public MemoryHandler(Handler target, int size, Level pushLevel) {
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if (target == null || pushLevel == null) {
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throw new NullPointerException();
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}
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if (size <= 0) {
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throw new IllegalArgumentException();
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}
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sealed = false;
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configure();
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sealed = true;
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this.target = target;
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this.pushLevel = pushLevel;
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this.size = size;
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init();
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}
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/**
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* Store a <tt>LogRecord</tt> in an internal buffer.
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* <p>
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* If there is a <tt>Filter</tt>, its <tt>isLoggable</tt>
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* method is called to check if the given log record is loggable.
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* If not we return. Otherwise the given record is copied into
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* an internal circular buffer. Then the record's level property is
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* compared with the <tt>pushLevel</tt>. If the given level is
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* greater than or equal to the <tt>pushLevel</tt> then <tt>push</tt>
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* is called to write all buffered records to the target output
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* <tt>Handler</tt>.
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*
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* @param record description of the log event. A null record is
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* silently ignored and is not published
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*/
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public synchronized void publish(LogRecord record) {
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if (!isLoggable(record)) {
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return;
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}
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int ix = (start+count)%buffer.length;
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buffer[ix] = record;
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if (count < buffer.length) {
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count++;
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} else {
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start++;
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start %= buffer.length;
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}
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if (record.getLevel().intValue() >= pushLevel.intValue()) {
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push();
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}
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}
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/**
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* Push any buffered output to the target <tt>Handler</tt>.
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* <p>
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* The buffer is then cleared.
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*/
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public synchronized void push() {
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for (int i = 0; i < count; i++) {
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int ix = (start+i)%buffer.length;
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LogRecord record = buffer[ix];
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target.publish(record);
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}
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// Empty the buffer.
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start = 0;
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count = 0;
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}
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/**
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* Causes a flush on the target <tt>Handler</tt>.
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* <p>
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* Note that the current contents of the <tt>MemoryHandler</tt>
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* buffer are <b>not</b> written out. That requires a "push".
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*/
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public void flush() {
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target.flush();
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}
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/**
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* Close the <tt>Handler</tt> and free all associated resources.
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* This will also close the target <tt>Handler</tt>.
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*
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* @exception SecurityException if a security manager exists and if
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* the caller does not have <tt>LoggingPermission("control")</tt>.
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*/
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public void close() throws SecurityException {
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target.close();
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setLevel(Level.OFF);
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}
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/**
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* Set the <tt>pushLevel</tt>. After a <tt>LogRecord</tt> is copied
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* into our internal buffer, if its level is greater than or equal to
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* the <tt>pushLevel</tt>, then <tt>push</tt> will be called.
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*
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* @param newLevel the new value of the <tt>pushLevel</tt>
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* @exception SecurityException if a security manager exists and if
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* the caller does not have <tt>LoggingPermission("control")</tt>.
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*/
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public void setPushLevel(Level newLevel) throws SecurityException {
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if (newLevel == null) {
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throw new NullPointerException();
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}
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LogManager manager = LogManager.getLogManager();
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checkAccess();
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pushLevel = newLevel;
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}
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/**
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* Get the <tt>pushLevel</tt>.
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*
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* @return the value of the <tt>pushLevel</tt>
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*/
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public synchronized Level getPushLevel() {
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return pushLevel;
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}
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/**
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* Check if this <tt>Handler</tt> would actually log a given
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* <tt>LogRecord</tt> into its internal buffer.
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* <p>
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* This method checks if the <tt>LogRecord</tt> has an appropriate level and
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* whether it satisfies any <tt>Filter</tt>. However it does <b>not</b>
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* check whether the <tt>LogRecord</tt> would result in a "push" of the
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* buffer contents. It will return false if the <tt>LogRecord</tt> is null.
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* <p>
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* @param record a <tt>LogRecord</tt>
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* @return true if the <tt>LogRecord</tt> would be logged.
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*
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*/
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public boolean isLoggable(LogRecord record) {
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return super.isLoggable(record);
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}
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}
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