001/**
002 * Copyright (c) 2004-2011 QOS.ch
003 * All rights reserved.
004 *
005 * Permission is hereby granted, free  of charge, to any person obtaining
006 * a  copy  of this  software  and  associated  documentation files  (the
007 * "Software"), to  deal in  the Software without  restriction, including
008 * without limitation  the rights to  use, copy, modify,  merge, publish,
009 * distribute,  sublicense, and/or sell  copies of  the Software,  and to
010 * permit persons to whom the Software  is furnished to do so, subject to
011 * the following conditions:
012 *
013 * The  above  copyright  notice  and  this permission  notice  shall  be
014 * included in all copies or substantial portions of the Software.
015 *
016 * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
017 * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
018 * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
019 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
020 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
021 * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
022 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
023 *
024 */
025package org.slf4j.helpers;
026
027/**
028 * An internal utility class.
029 *
030 * @author Alexander Dorokhine
031 * @author Ceki Gülcü
032 */
033public final class Util {
034
035        
036    private Util() {
037    }
038
039    public static String safeGetSystemProperty(String key) {
040        if (key == null)
041            throw new IllegalArgumentException("null input");
042
043        String result = null;
044        try {
045            result = System.getProperty(key);
046        } catch (java.lang.SecurityException sm) {
047            ; // ignore
048        }
049        return result;
050    }
051
052    public static boolean safeGetBooleanSystemProperty(String key) {
053        String value = safeGetSystemProperty(key);
054        if (value == null)
055            return false;
056        else
057            return value.equalsIgnoreCase("true");
058    }
059
060    /**
061     * In order to call {@link SecurityManager#getClassContext()}, which is a
062     * protected method, we add this wrapper which allows the method to be visible
063     * inside this package.
064     */
065    private static final class ClassContextSecurityManager extends SecurityManager {
066        protected Class<?>[] getClassContext() {
067            return super.getClassContext();
068        }
069    }
070
071    private static ClassContextSecurityManager SECURITY_MANAGER;
072    private static boolean SECURITY_MANAGER_CREATION_ALREADY_ATTEMPTED = false;
073
074    private static ClassContextSecurityManager getSecurityManager() {
075        if (SECURITY_MANAGER != null)
076            return SECURITY_MANAGER;
077        else if (SECURITY_MANAGER_CREATION_ALREADY_ATTEMPTED)
078            return null;
079        else {
080            SECURITY_MANAGER = safeCreateSecurityManager();
081            SECURITY_MANAGER_CREATION_ALREADY_ATTEMPTED = true;
082            return SECURITY_MANAGER;
083        }
084    }
085
086    private static ClassContextSecurityManager safeCreateSecurityManager() {
087        try {
088            return new ClassContextSecurityManager();
089        } catch (java.lang.SecurityException sm) {
090            return null;
091        }
092    }
093
094    /**
095     * Returns the name of the class which called the invoking method.
096     *
097     * @return the name of the class which called the invoking method.
098     */
099    public static Class<?> getCallingClass() {
100        ClassContextSecurityManager securityManager = getSecurityManager();
101        if (securityManager == null)
102            return null;
103        Class<?>[] trace = securityManager.getClassContext();
104        String thisClassName = Util.class.getName();
105
106        // Advance until Util is found
107        int i;
108        for (i = 0; i < trace.length; i++) {
109            if (thisClassName.equals(trace[i].getName()))
110                break;
111        }
112
113        // trace[i] = Util; trace[i+1] = caller; trace[i+2] = caller's caller
114        if (i >= trace.length || i + 2 >= trace.length) {
115            throw new IllegalStateException("Failed to find org.slf4j.helpers.Util or its caller in the stack; " + "this should not happen");
116        }
117
118        return trace[i + 2];
119    }
120
121    static final public void report(String msg, Throwable t) {
122        System.err.println(msg);
123        System.err.println("Reported exception:");
124        t.printStackTrace();
125    }
126
127    static final public void report(String msg) {
128        System.err.println("SLF4J: " + msg);
129    }
130    
131        
132
133}