001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.configuration2.io; 019 020import org.apache.commons.logging.Log; 021import org.apache.commons.logging.LogFactory; 022import org.apache.commons.logging.impl.NoOpLog; 023 024/** 025 * <p> 026 * A class providing basic logging capabilities. 027 * </p> 028 * <p> 029 * When reading configuration files in complex scenarios having log output is useful for diagnostic purposes. Therefore, 030 * <em>Commons Configuration</em> produces some logging output. As concrete projects have different requirements on the 031 * amount and detail of logging, there is a way of configuring logging: All classes derived from 032 * {@link org.apache.commons.configuration2.AbstractConfiguration} can be assigned a logger which is then used for all 033 * log statements generated. 034 * </p> 035 * <p> 036 * Allowing a logger object to be passed to a configuration creates a direct dependency to a concrete logging framework 037 * in the configuration API. This would make it impossible to switch to an alternative logging framework without 038 * breaking backwards compatibility. To avoid this, the {@code ConfigurationLogger} class is introduced. It is a minimum 039 * abstraction over a logging framework offering only very basic logging capabilities. The methods defined in this class 040 * are used by configuration implementations to produce their logging statements. Client applications can create 041 * specialized instances and pass them to configuration objects without having to deal with a concrete logging 042 * framework. It is even possible to create a subclass that uses a completely different logging framework. 043 * </p> 044 * 045 * @since 2.0 046 */ 047public class ConfigurationLogger { 048 /** The internal logger. */ 049 private final Log log; 050 051 /** 052 * Creates a new instance of {@code ConfigurationLogger} that uses the specified logger name. 053 * 054 * @param loggerName the logger name (must not be <b>null</b>) 055 * @throws IllegalArgumentException if the logger name is <b>null</b> 056 */ 057 public ConfigurationLogger(final String loggerName) { 058 this(createLoggerForName(loggerName)); 059 } 060 061 /** 062 * Creates a new instance of {@code ConfigurationLogger} that uses a logger whose name is derived from the provided 063 * class. 064 * 065 * @param logCls the class whose name is to be used for logging (must not be <b>null</b>) 066 * @throws IllegalArgumentException if the logger class is <b>null</b> 067 */ 068 public ConfigurationLogger(final Class<?> logCls) { 069 this(createLoggerForClass(logCls)); 070 } 071 072 /** 073 * Creates a new, uninitialized instance of {@code ConfigurationLogger}. This constructor can be used by derived classes 074 * that implement their own specific logging mechanism. Such classes must override all methods because the default 075 * implementations do not work in this uninitialized state. 076 */ 077 protected ConfigurationLogger() { 078 this((Log) null); 079 } 080 081 /** 082 * Creates a new instance of {@code ConfigurationLogger} which wraps the specified logger. 083 * 084 * @param wrapped the logger to be wrapped 085 */ 086 ConfigurationLogger(final Log wrapped) { 087 log = wrapped; 088 } 089 090 /** 091 * Creates a new dummy logger which produces no output. If such a logger is passed to a configuration object, logging is 092 * effectively disabled. 093 * 094 * @return the new dummy logger 095 */ 096 public static ConfigurationLogger newDummyLogger() { 097 return new ConfigurationLogger(new NoOpLog()); 098 } 099 100 /** 101 * Returns a flag whether logging on debug level is enabled. 102 * 103 * @return <b>true</b> if debug logging is enabled, <b>false</b> otherwise 104 */ 105 public boolean isDebugEnabled() { 106 return getLog().isDebugEnabled(); 107 } 108 109 /** 110 * Logs the specified message on debug level. 111 * 112 * @param msg the message to be logged 113 */ 114 public void debug(final String msg) { 115 getLog().debug(msg); 116 } 117 118 /** 119 * Returns a flag whether logging on info level is enabled. 120 * 121 * @return <b>true</b> if debug logging is enabled, <b>false</b> otherwise 122 */ 123 public boolean isInfoEnabled() { 124 return getLog().isInfoEnabled(); 125 } 126 127 /** 128 * Logs the specified message on info level. 129 * 130 * @param msg the message to be logged 131 */ 132 public void info(final String msg) { 133 getLog().info(msg); 134 } 135 136 /** 137 * Logs the specified message on warn level. 138 * 139 * @param msg the message to be logged 140 */ 141 public void warn(final String msg) { 142 getLog().warn(msg); 143 } 144 145 /** 146 * Logs the specified exception on warn level. 147 * 148 * @param msg the message to be logged 149 * @param ex the exception to be logged 150 */ 151 public void warn(final String msg, final Throwable ex) { 152 getLog().warn(msg, ex); 153 } 154 155 /** 156 * Logs the specified message on error level. 157 * 158 * @param msg the message to be logged 159 */ 160 public void error(final String msg) { 161 getLog().error(msg); 162 } 163 164 /** 165 * Logs the specified exception on error level. 166 * 167 * @param msg the message to be logged 168 * @param ex the exception to be logged 169 */ 170 public void error(final String msg, final Throwable ex) { 171 getLog().error(msg, ex); 172 } 173 174 /** 175 * Gets the internal logger. 176 * 177 * @return the internal logger 178 */ 179 Log getLog() { 180 return log; 181 } 182 183 /** 184 * Creates an internal logger for the given name. Throws an exception if the name is undefined. 185 * 186 * @param name the name of the logger 187 * @return the logger object 188 * @throws IllegalArgumentException if the logger name is undefined 189 */ 190 private static Log createLoggerForName(final String name) { 191 if (name == null) { 192 throw new IllegalArgumentException("Logger name must not be null!"); 193 } 194 return LogFactory.getLog(name); 195 } 196 197 /** 198 * Creates an internal logger for the given class. Throws an exception if the class is undefined. 199 * 200 * @param cls the logger class 201 * @return the logger object 202 * @throws IllegalArgumentException if the logger class is undefined 203 */ 204 private static Log createLoggerForClass(final Class<?> cls) { 205 if (cls == null) { 206 throw new IllegalArgumentException("Logger class must not be null!"); 207 } 208 return LogFactory.getLog(cls); 209 } 210}