| 1 | package org.apache.velocity.runtime.log; |
| 2 | |
| 3 | /* |
| 4 | * Copyright 2001,2004 The Apache Software Foundation. |
| 5 | * |
| 6 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 7 | * you may not use this file except in compliance with the License. |
| 8 | * You may obtain a copy of the License at |
| 9 | * |
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | * |
| 12 | * Unless required by applicable law or agreed to in writing, software |
| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | * See the License for the specific language governing permissions and |
| 16 | * limitations under the License. |
| 17 | */ |
| 18 | |
| 19 | import java.util.List; |
| 20 | import java.util.ArrayList; |
| 21 | import java.util.Iterator; |
| 22 | |
| 23 | import org.apache.velocity.runtime.RuntimeServices; |
| 24 | import org.apache.velocity.runtime.RuntimeConstants; |
| 25 | |
| 26 | /** |
| 27 | * <p> |
| 28 | * This class is responsible for instantiating the correct LoggingSystem |
| 29 | * </p> |
| 30 | * |
| 31 | * <p> |
| 32 | * The approach is : |
| 33 | * </p> |
| 34 | * <ul> |
| 35 | * <li> |
| 36 | * First try to see if the user is passing in a living object |
| 37 | * that is a LogSystem, allowing the app to give is living |
| 38 | * custom loggers. |
| 39 | * </li> |
| 40 | * <li> |
| 41 | * Next, run through the (possible) list of classes specified |
| 42 | * specified as loggers, taking the first one that appears to |
| 43 | * work. This is how we support finding either log4j or |
| 44 | * logkit, whichever is in the classpath, as both are |
| 45 | * listed as defaults. |
| 46 | * </li> |
| 47 | * <li> |
| 48 | * Finally, we turn to 'faith-based' logging, and hope that |
| 49 | * logkit is in the classpath, and try for an AvalonLogSystem |
| 50 | * as a final gasp. After that, there is nothing we can do. |
| 51 | * </li> |
| 52 | * |
| 53 | * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> |
| 54 | * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a> |
| 55 | * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> |
| 56 | * @version $Id: LogManager.java,v 1.10.4.1 2004/03/03 23:22:56 geirm Exp $ |
| 57 | */ |
| 58 | public class LogManager |
| 59 | { |
| 60 | /** |
| 61 | * Creates a new logging system or returns an existing one |
| 62 | * specified by the application. |
| 63 | */ |
| 64 | public static LogSystem createLogSystem( RuntimeServices rsvc ) |
| 65 | throws Exception |
| 66 | { |
| 67 | /* |
| 68 | * if a logSystem was set as a configuation value, use that. |
| 69 | * This is any class the user specifies. |
| 70 | */ |
| 71 | |
| 72 | Object o = rsvc.getProperty( RuntimeConstants.RUNTIME_LOG_LOGSYSTEM ); |
| 73 | |
| 74 | if (o != null && o instanceof LogSystem) |
| 75 | { |
| 76 | ((LogSystem) o).init( rsvc ); |
| 77 | |
| 78 | return (LogSystem) o; |
| 79 | } |
| 80 | |
| 81 | /* |
| 82 | * otherwise, see if a class was specified. You |
| 83 | * can put multiple classes, and we use the first one we find. |
| 84 | * |
| 85 | * Note that the default value of this property contains both the |
| 86 | * AvalonLogSystem and the SimpleLog4JLogSystem for convenience - |
| 87 | * so we use whichever we find. |
| 88 | */ |
| 89 | |
| 90 | List classes = null; |
| 91 | Object obj = rsvc.getProperty( RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS ); |
| 92 | |
| 93 | /* |
| 94 | * we might have a list, or not - so check |
| 95 | */ |
| 96 | |
| 97 | if ( obj instanceof List) |
| 98 | { |
| 99 | classes = (List) obj; |
| 100 | } |
| 101 | else if ( obj instanceof String) |
| 102 | { |
| 103 | classes = new ArrayList(); |
| 104 | classes.add( obj ); |
| 105 | } |
| 106 | |
| 107 | /* |
| 108 | * now run through the list, trying each. It's ok to |
| 109 | * fail with a class not found, as we do this to also |
| 110 | * search out a default simple file logger |
| 111 | */ |
| 112 | |
| 113 | for( Iterator ii = classes.iterator(); ii.hasNext(); ) |
| 114 | { |
| 115 | String claz = (String) ii.next(); |
| 116 | |
| 117 | if (claz != null && claz.length() > 0 ) |
| 118 | { |
| 119 | rsvc.info("Trying to use logger class " + claz ); |
| 120 | |
| 121 | try |
| 122 | { |
| 123 | o = Class.forName( claz ).newInstance(); |
| 124 | |
| 125 | if ( o instanceof LogSystem ) |
| 126 | { |
| 127 | ((LogSystem) o).init( rsvc ); |
| 128 | |
| 129 | rsvc.info("Using logger class " + claz ); |
| 130 | |
| 131 | return (LogSystem) o; |
| 132 | } |
| 133 | else |
| 134 | { |
| 135 | rsvc.error("The specifid logger class " + claz + |
| 136 | " isn't a valid LogSystem"); |
| 137 | } |
| 138 | } |
| 139 | catch( NoClassDefFoundError ncdfe ) |
| 140 | { |
| 141 | rsvc.debug("Couldn't find class " + claz |
| 142 | + " or necessary supporting classes in " |
| 143 | + "classpath. Exception : " + ncdfe); |
| 144 | } |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | /* |
| 149 | * if the above failed, then we are in deep doo-doo, as the |
| 150 | * above means that either the user specified a logging class |
| 151 | * that we can't find, there weren't the necessary |
| 152 | * dependencies in the classpath for it, or there were no |
| 153 | * dependencies for the default loggers, log4j and logkit. |
| 154 | * Since we really don't know, |
| 155 | * then take a wack at the AvalonLogSystem as a last resort. |
| 156 | */ |
| 157 | |
| 158 | LogSystem als = null; |
| 159 | |
| 160 | try |
| 161 | { |
| 162 | als = new AvalonLogSystem(); |
| 163 | |
| 164 | als.init( rsvc ); |
| 165 | } |
| 166 | catch( NoClassDefFoundError ncdfe ) |
| 167 | { |
| 168 | String errstr = "PANIC : Velocity cannot find any of the" |
| 169 | + " specified or default logging systems in the classpath," |
| 170 | + " or the classpath doesn't contain the necessary classes" |
| 171 | + " to support them." |
| 172 | + " Please consult the documentation regarding logging." |
| 173 | + " Exception : " + ncdfe; |
| 174 | |
| 175 | System.out.println( errstr ); |
| 176 | System.err.println( errstr ); |
| 177 | |
| 178 | throw ncdfe; |
| 179 | } |
| 180 | |
| 181 | rsvc.info("Using AvalonLogSystem as logger of final resort."); |
| 182 | |
| 183 | return als; |
| 184 | } |
| 185 | } |
| 186 | |