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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.configuration2.io;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.impl.NoOpLog;
/**
*
* A class providing basic logging capabilities.
*
*
* When reading configuration files in complex scenarios having log output is
* useful for diagnostic purposes. Therefore, Commons Configuration
* produces some logging output. As concrete projects have different
* requirements on the amount and detail of logging, there is a way of
* configuring logging: All classes derived from
* {@link org.apache.commons.configuration2.AbstractConfiguration}
* can be assigned a logger which is then used for all log statements generated.
*
*
* Allowing a logger object to be passed to a configuration creates a direct
* dependency to a concrete logging framework in the configuration API. This
* would make it impossible to switch to an alternative logging framework
* without breaking backwards compatibility. To avoid this, the
* {@code ConfigurationLogger} class is introduced. It is a minimum abstraction
* over a logging framework offering only very basic logging capabilities. The
* methods defined in this class are used by configuration implementations to
* produce their logging statements. Client applications can create specialized
* instances and pass them to configuration objects without having to deal with
* a concrete logging framework. It is even possible to create a subclass that
* uses a completely different logging framework.
*
*
* @since 2.0
*/
public class ConfigurationLogger
{
/** The internal logger. */
private final Log log;
/**
* Creates a new instance of {@code ConfigurationLogger} that uses the
* specified logger name.
*
* @param loggerName the logger name (must not be null)
* @throws IllegalArgumentException if the logger name is null
*/
public ConfigurationLogger(final String loggerName)
{
this(createLoggerForName(loggerName));
}
/**
* Creates a new instance of {@code ConfigurationLogger} that uses a logger
* whose name is derived from the provided class.
*
* @param logCls the class whose name is to be used for logging (must not be
* null)
* @throws IllegalArgumentException if the logger class is null
*/
public ConfigurationLogger(final Class logCls)
{
this(createLoggerForClass(logCls));
}
/**
* Creates a new, uninitialized instance of {@code ConfigurationLogger}.
* This constructor can be used by derived classes that implement their own
* specific logging mechanism. Such classes must override all methods
* because the default implementations do not work in this uninitialized
* state.
*/
protected ConfigurationLogger()
{
this((Log) null);
}
/**
* Creates a new instance of {@code ConfigurationLogger} which wraps the
* specified logger.
*
* @param wrapped the logger to be wrapped
*/
ConfigurationLogger(final Log wrapped)
{
log = wrapped;
}
/**
* Creates a new dummy logger which produces no output. If such a logger is
* passed to a configuration object, logging is effectively disabled.
*
* @return the new dummy logger
*/
public static ConfigurationLogger newDummyLogger()
{
return new ConfigurationLogger(new NoOpLog());
}
/**
* Returns a flag whether logging on debug level is enabled.
*
* @return true if debug logging is enabled, false otherwise
*/
public boolean isDebugEnabled()
{
return getLog().isDebugEnabled();
}
/**
* Logs the specified message on debug level.
*
* @param msg the message to be logged
*/
public void debug(final String msg)
{
getLog().debug(msg);
}
/**
* Returns a flag whether logging on info level is enabled.
*
* @return true if debug logging is enabled, false otherwise
*/
public boolean isInfoEnabled()
{
return getLog().isInfoEnabled();
}
/**
* Logs the specified message on info level.
*
* @param msg the message to be logged
*/
public void info(final String msg)
{
getLog().info(msg);
}
/**
* Logs the specified message on warn level.
*
* @param msg the message to be logged
*/
public void warn(final String msg)
{
getLog().warn(msg);
}
/**
* Logs the specified exception on warn level.
*
* @param msg the message to be logged
* @param ex the exception to be logged
*/
public void warn(final String msg, final Throwable ex)
{
getLog().warn(msg, ex);
}
/**
* Logs the specified message on error level.
*
* @param msg the message to be logged
*/
public void error(final String msg)
{
getLog().error(msg);
}
/**
* Logs the specified exception on error level.
*
* @param msg the message to be logged
* @param ex the exception to be logged
*/
public void error(final String msg, final Throwable ex)
{
getLog().error(msg, ex);
}
/**
* Returns the internal logger.
*
* @return the internal logger
*/
Log getLog()
{
return log;
}
/**
* Creates an internal logger for the given name. Throws an exception if the
* name is undefined.
*
* @param name the name of the logger
* @return the logger object
* @throws IllegalArgumentException if the logger name is undefined
*/
private static Log createLoggerForName(final String name)
{
if (name == null)
{
throw new IllegalArgumentException("Logger name must not be null!");
}
return LogFactory.getLog(name);
}
/**
* Creates an internal logger for the given class. Throws an exception if
* the class is undefined.
*
* @param cls the logger class
* @return the logger object
* @throws IllegalArgumentException if the logger class is undefined
*/
private static Log createLoggerForClass(final Class cls)
{
if (cls == null)
{
throw new IllegalArgumentException(
"Logger class must not be null!");
}
return LogFactory.getLog(cls);
}
}