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 * Copyright (c) 2009, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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package sun.util.logging;

import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Date;

Internal API to support JRE implementation to detect if the java.util.logging support is available but with no dependency on the java.util.logging classes. This LoggingSupport class provides several static methods to access the java.util.logging functionality that requires the caller to ensure that the logging support is available before invoking it. 
See Also:
if you want to log messages even
if the logging support is not available/**
 * Internal API to support JRE implementation to detect if the java.util.logging
 * support is available but with no dependency on the java.util.logging
 * classes.  This LoggingSupport class provides several static methods to
 * access the java.util.logging functionality that requires the caller
 * to ensure that the logging support is {@linkplain #isAvailable available}
 * before invoking it.
 *
 * @see sun.util.logging.PlatformLogger if you want to log messages even
 * if the logging support is not available
 */
public class LoggingSupport {
    private LoggingSupport() { }

    private static final LoggingProxy proxy =
        AccessController.doPrivileged(new PrivilegedAction<LoggingProxy>() {
            public LoggingProxy run() {
                try {
                    // create a LoggingProxyImpl instance when
                    // java.util.logging classes exist
                    Class<?> c = Class.forName("java.util.logging.LoggingProxyImpl", true, null);
                    Field f = c.getDeclaredField("INSTANCE");
                    f.setAccessible(true);
                    return (LoggingProxy) f.get(null);
                } catch (ClassNotFoundException cnf) {
                    return null;
                } catch (NoSuchFieldException e) {
                    throw new AssertionError(e);
                } catch (IllegalAccessException e) {
                    throw new AssertionError(e);
                }
            }});

    
Returns true if java.util.logging support is available.
/**
     * Returns true if java.util.logging support is available.
     */
    public static boolean isAvailable() {
        return proxy != null;
    }

    private static void ensureAvailable() {
        if (proxy == null)
            throw new AssertionError("Should not here");
    }

    public static java.util.List<String> getLoggerNames() {
        ensureAvailable();
        return proxy.getLoggerNames();
    }
    public static String getLoggerLevel(String loggerName) {
        ensureAvailable();
        return proxy.getLoggerLevel(loggerName);
    }

    public static void setLoggerLevel(String loggerName, String levelName) {
        ensureAvailable();
        proxy.setLoggerLevel(loggerName, levelName);
    }

    public static String getParentLoggerName(String loggerName) {
        ensureAvailable();
        return proxy.getParentLoggerName(loggerName);
    }

    public static Object getLogger(String name) {
        ensureAvailable();
        return proxy.getLogger(name);
    }

    public static Object getLevel(Object logger) {
        ensureAvailable();
        return proxy.getLevel(logger);
    }

    public static void setLevel(Object logger, Object newLevel) {
        ensureAvailable();
        proxy.setLevel(logger, newLevel);
    }

    public static boolean isLoggable(Object logger, Object level) {
        ensureAvailable();
        return proxy.isLoggable(logger,level);
    }

    public static void log(Object logger, Object level, String msg) {
        ensureAvailable();
        proxy.log(logger, level, msg);
    }

    public static void log(Object logger, Object level, String msg, Throwable t) {
        ensureAvailable();
        proxy.log(logger, level, msg, t);
    }

    public static void log(Object logger, Object level, String msg, Object... params) {
        ensureAvailable();
        proxy.log(logger, level, msg, params);
    }

    public static Object parseLevel(String levelName) {
        ensureAvailable();
        return proxy.parseLevel(levelName);
    }

    public static String getLevelName(Object level) {
        ensureAvailable();
        return proxy.getLevelName(level);
    }

    public static int getLevelValue(Object level) {
        ensureAvailable();
        return proxy.getLevelValue(level);
    }

    private static final String DEFAULT_FORMAT =
        "%1$tb %1$td, %1$tY %1$tl:%1$tM:%1$tS %1$Tp %2$s%n%4$s: %5$s%6$s%n";

    private static final String FORMAT_PROP_KEY = "java.util.logging.SimpleFormatter.format";
    public static String getSimpleFormat() {
        return getSimpleFormat(true);
    }

    // useProxy if true will cause initialization of
    // java.util.logging and read its configuration
    static String getSimpleFormat(boolean useProxy) {
        String format =
            AccessController.doPrivileged(
                new PrivilegedAction<String>() {
                    public String run() {
                        return System.getProperty(FORMAT_PROP_KEY);
                    }
                });

        if (useProxy && proxy != null && format == null) {
            format = proxy.getProperty(FORMAT_PROP_KEY);
        }

        if (format != null) {
            try {
                // validate the user-defined format string
                String.format(format, new Date(), "", "", "", "", "");
            } catch (IllegalArgumentException e) {
                // illegal syntax; fall back to the default format
                format = DEFAULT_FORMAT;
            }
        } else {
            format = DEFAULT_FORMAT;
        }
        return format;
    }

}