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Java example source code file (Handler.java)
The Handler.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; import java.io.UnsupportedEncodingException; /** * A <tt>Handler object takes log messages from a Logger and * exports them. It might for example, write them to a console * or write them to a file, or send them to a network logging service, * or forward them to an OS log, or whatever. * <p> * A <tt>Handler can be disabled by doing a setLevel(Level.OFF) * and can be re-enabled by doing a <tt>setLevel with an appropriate level. * <p> * <tt>Handler classes typically use LogManager properties to set * default values for the <tt>Handler's Filter, Formatter, * and <tt>Level. See the specific documentation for each concrete * <tt>Handler class. * * * @since 1.4 */ public abstract class Handler { private static final int offValue = Level.OFF.intValue(); private final LogManager manager = LogManager.getLogManager(); // We're using volatile here to avoid synchronizing getters, which // would prevent other threads from calling isLoggable() // while publish() is executing. // On the other hand, setters will be synchronized to exclude concurrent // execution with more complex methods, such as StreamHandler.publish(). // We wouldn't want 'level' to be changed by another thread in the middle // of the execution of a 'publish' call. private volatile Filter filter; private volatile Formatter formatter; private volatile Level logLevel = Level.ALL; private volatile ErrorManager errorManager = new ErrorManager(); private volatile String encoding; // Package private support for security checking. When sealed // is true, we access check updates to the class. boolean sealed = true; /** * Default constructor. The resulting <tt>Handler has a log * level of <tt>Level.ALL, no Formatter, and no * <tt>Filter. A default ErrorManager instance is installed * as the <tt>ErrorManager. */ protected Handler() { } /** * Publish a <tt>LogRecord. * <p> * The logging request was made initially to a <tt>Logger object, * which initialized the <tt>LogRecord and forwarded it here. * <p> * The <tt>Handler is responsible for formatting the message, when and * if necessary. The formatting should include localization. * * @param record description of the log event. A null record is * silently ignored and is not published */ public abstract void publish(LogRecord record); /** * Flush any buffered output. */ public abstract void flush(); /** * Close the <tt>Handler and free all associated resources. * <p> * The close method will perform a <tt>flush and then close the * <tt>Handler. After close has been called this Handler * should no longer be used. Method calls may either be silently * ignored or may throw runtime exceptions. * * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public abstract void close() throws SecurityException; /** * Set a <tt>Formatter. This Formatter will be used * to format <tt>LogRecords for this Handler. * <p> * Some <tt>Handlers may not use Formatters, in * which case the <tt>Formatter will be remembered, but not used. * <p> * @param newFormatter the <tt>Formatter to use (may not be null) * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public synchronized void setFormatter(Formatter newFormatter) throws SecurityException { checkPermission(); // Check for a null pointer: newFormatter.getClass(); formatter = newFormatter; } /** * Return the <tt>Formatter for this Handler. * @return the <tt>Formatter (may be null). */ public Formatter getFormatter() { return formatter; } /** * Set the character encoding used by this <tt>Handler. * <p> * The encoding should be set before any <tt>LogRecords are written * to the <tt>Handler. * * @param encoding The name of a supported character encoding. * May be null, to indicate the default platform encoding. * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). * @exception UnsupportedEncodingException if the named encoding is * not supported. */ public synchronized void setEncoding(String encoding) throws SecurityException, java.io.UnsupportedEncodingException { checkPermission(); if (encoding != null) { try { if(!java.nio.charset.Charset.isSupported(encoding)) { throw new UnsupportedEncodingException(encoding); } } catch (java.nio.charset.IllegalCharsetNameException e) { throw new UnsupportedEncodingException(encoding); } } this.encoding = encoding; } /** * Return the character encoding for this <tt>Handler. * * @return The encoding name. May be null, which indicates the * default encoding should be used. */ public String getEncoding() { return encoding; } /** * Set a <tt>Filter to control output on this Handler. * <P> * For each call of <tt>publish the Handler will call * this <tt>Filter (if it is non-null) to check if the * <tt>LogRecord should be published or discarded. * * @param newFilter a <tt>Filter object (may be null) * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public synchronized void setFilter(Filter newFilter) throws SecurityException { checkPermission(); filter = newFilter; } /** * Get the current <tt>Filter for this Handler. * * @return a <tt>Filter object (may be null) */ public Filter getFilter() { return filter; } /** * Define an ErrorManager for this Handler. * <p> * The ErrorManager's "error" method will be invoked if any * errors occur while using this Handler. * * @param em the new ErrorManager * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public synchronized void setErrorManager(ErrorManager em) { checkPermission(); if (em == null) { throw new NullPointerException(); } errorManager = em; } /** * Retrieves the ErrorManager for this Handler. * * @return the ErrorManager for this Handler * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public ErrorManager getErrorManager() { checkPermission(); return errorManager; } /** * Protected convenience method to report an error to this Handler's * ErrorManager. Note that this method retrieves and uses the ErrorManager * without doing a security check. It can therefore be used in * environments where the caller may be non-privileged. * * @param msg a descriptive string (may be null) * @param ex an exception (may be null) * @param code an error code defined in ErrorManager */ protected void reportError(String msg, Exception ex, int code) { try { errorManager.error(msg, ex, code); } catch (Exception ex2) { System.err.println("Handler.reportError caught:"); ex2.printStackTrace(); } } /** * Set the log level specifying which message levels will be * logged by this <tt>Handler. Message levels lower than this * value will be discarded. * <p> * The intention is to allow developers to turn on voluminous * logging, but to limit the messages that are sent to certain * <tt>Handlers. * * @param newLevel the new value for the log level * @exception SecurityException if a security manager exists and if * the caller does not have <tt>LoggingPermission("control"). */ public synchronized void setLevel(Level newLevel) throws SecurityException { if (newLevel == null) { throw new NullPointerException(); } checkPermission(); logLevel = newLevel; } /** * Get the log level specifying which messages will be * logged by this <tt>Handler. Message levels lower * than this level will be discarded. * @return the level of messages being logged. */ public Level getLevel() { return logLevel; } /** * Check if this <tt>Handler would actually log a given LogRecord. * <p> * This method checks if the <tt>LogRecord has an appropriate * <tt>Level and whether it satisfies any Filter. It also * may make other <tt>Handler specific checks that might prevent a * handler from logging the <tt>LogRecord. 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. * */ public boolean isLoggable(LogRecord record) { final int levelValue = getLevel().intValue(); if (record.getLevel().intValue() < levelValue || levelValue == offValue) { return false; } final Filter filter = getFilter(); if (filter == null) { return true; } return filter.isLoggable(record); } // Package-private support method for security checks. // If "sealed" is true, we check that the caller has // appropriate security privileges to update Handler // state and if not throw a SecurityException. void checkPermission() throws SecurityException { if (sealed) { manager.checkPermission(); } } } Other Java examples (source code examples)Here is a short list of links related to this Java Handler.java source code file: |
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