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Java example source code file (MemoryHandler.java)
The MemoryHandler.java Java example source code/* * Copyright (c) 2000, 2013, 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; /** * <tt>Handler that buffers requests in a circular buffer in memory. * <p> * Normally this <tt>Handler simply stores incoming LogRecords * into its memory buffer and discards earlier records. This buffering * is very cheap and avoids formatting costs. On certain trigger * conditions, the <tt>MemoryHandler will push out its current buffer * contents to a target <tt>Handler, which will typically publish * them to the outside world. * <p> * There are three main models for triggering a push of the buffer: * <ul> * <li> * An incoming <tt>LogRecord has a type that is greater than * a pre-defined level, the <tt>pushLevel. * <li> * An external class calls the <tt>push method explicitly. * <li> * A subclass overrides the <tt>log method and scans each incoming * <tt>LogRecord and calls push if a record matches some * desired criteria. </li> * </ul> * <p> * <b>Configuration: * By default each <tt>MemoryHandler is initialized using the following * <tt>LogManager configuration properties where <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. * If no default value is defined then a RuntimeException is thrown. * <ul> * <li> <handler-name>.level * specifies the level for the <tt>Handler * (defaults to <tt>Level.ALL). * <li> <handler-name>.filter * specifies the name of a <tt>Filter class to use * (defaults to no <tt>Filter). * <li> <handler-name>.size * defines the buffer size (defaults to 1000). </li> * <li> <handler-name>.push * defines the <tt>pushLevel (defaults to level.SEVERE). * <li> <handler-name>.target * specifies the name of the target <tt>Handler class. * (no default). </li> * </ul> * <p> * For example, the properties for {@code MemoryHandler} would be: * <ul> * <li> java.util.logging.MemoryHandler.level=INFO * <li> java.util.logging.MemoryHandler.formatter=java.util.logging.SimpleFormatter * </ul> * <p> * For a custom handler, e.g. com.foo.MyHandler, the properties would be: * <ul> * <li> com.foo.MyHandler.level=INFO * <li> com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter * </ul> * <p> * @since 1.4 */ public class MemoryHandler extends Handler { private final static int DEFAULT_SIZE = 1000; private volatile Level pushLevel; private int size; private Handler target; private LogRecord buffer[]; int start, count; // Private method to configure a MemoryHandler from LogManager // properties and/or default values as specified in the class // javadoc. private void configure() { LogManager manager = LogManager.getLogManager(); String cname = getClass().getName(); pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE); size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE); if (size <= 0) { size = DEFAULT_SIZE; } setLevel(manager.getLevelProperty(cname +".level", Level.ALL)); setFilter(manager.getFilterProperty(cname +".filter", null)); setFormatter(manager.getFormatterProperty(cname +".formatter", new SimpleFormatter())); } /** * Create a <tt>MemoryHandler and configure it based on * <tt>LogManager configuration properties. */ public MemoryHandler() { sealed = false; configure(); sealed = true; LogManager manager = LogManager.getLogManager(); String handlerName = getClass().getName(); String targetName = manager.getProperty(handlerName+".target"); if (targetName == null) { throw new RuntimeException("The handler " + handlerName + " does not specify a target"); } Class<?> clz; try { clz = ClassLoader.getSystemClassLoader().loadClass(targetName); target = (Handler) clz.newInstance(); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) { throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e); } init(); } // Initialize. Size is a count of LogRecords. private void init() { buffer = new LogRecord[size]; start = 0; count = 0; } /** * Create a <tt>MemoryHandler. * <p> * The <tt>MemoryHandler is configured based on LogManager * properties (or their default values) except that the given <tt>pushLevel * argument and buffer size argument are used. * * @param target the Handler to which to publish output. * @param size the number of log records to buffer (must be greater than zero) * @param pushLevel message level to push on * * @throws IllegalArgumentException if {@code size is <= 0} */ public MemoryHandler(Handler target, int size, Level pushLevel) { if (target == null || pushLevel == null) { throw new NullPointerException(); } if (size <= 0) { throw new IllegalArgumentException(); } sealed = false; configure(); sealed = true; this.target = target; this.pushLevel = pushLevel; this.size = size; init(); } /** * Store a <tt>LogRecord in an internal buffer. * <p> * If there is a <tt>Filter, its isLoggable * method is called to check if the given log record is loggable. * If not we return. Otherwise the given record is copied into * an internal circular buffer. Then the record's level property is * compared with the <tt>pushLevel. If the given level is * greater than or equal to the <tt>pushLevel then push * is called to write all buffered records to the target output * <tt>Handler. * * @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; } int ix = (start+count)%buffer.length; buffer[ix] = record; if (count < buffer.length) { count++; } else { start++; start %= buffer.length; } if (record.getLevel().intValue() >= pushLevel.intValue()) { push(); } } /** * Push any buffered output to the target <tt>Handler. * <p> * The buffer is then cleared. */ public synchronized void push() { for (int i = 0; i < count; i++) { int ix = (start+i)%buffer.length; LogRecord record = buffer[ix]; target.publish(record); } // Empty the buffer. start = 0; count = 0; } /** * Causes a flush on the target <tt>Handler. * <p> * Note that the current contents of the <tt>MemoryHandler * buffer are <b>not written out. That requires a "push". */ @Override public void flush() { target.flush(); } /** * Close the <tt>Handler and free all associated resources. * This will also close the target <tt>Handler. * * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ @Override public void close() throws SecurityException { target.close(); setLevel(Level.OFF); } /** * Set the <tt>pushLevel. After a LogRecord is copied * into our internal buffer, if its level is greater than or equal to * the <tt>pushLevel, then push will be called. * * @param newLevel the new value of the <tt>pushLevel * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public synchronized void setPushLevel(Level newLevel) throws SecurityException { if (newLevel == null) { throw new NullPointerException(); } checkPermission(); pushLevel = newLevel; } /** * Get the <tt>pushLevel. * * @return the value of the <tt>pushLevel */ public Level getPushLevel() { return pushLevel; } /** * Check if this <tt>Handler would actually log a given * <tt>LogRecord into its internal buffer. * <p> * This method checks if the <tt>LogRecord has an appropriate level and * whether it satisfies any <tt>Filter. However it does not * check whether the <tt>LogRecord would result in a "push" of the * buffer contents. It will return false if the <tt>LogRecord is null. * <p> * @param record a <tt>LogRecord * @return true if the <tt>LogRecord would be logged. * */ @Override public boolean isLoggable(LogRecord record) { return super.isLoggable(record); } } Other Java examples (source code examples)Here is a short list of links related to this Java MemoryHandler.java source code file: |
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