/*
* 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.felix.utils.log;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.log.LogService;
import java.io.PrintStream;
/**
* Internal logger to be used in order to avoid a mandatory dependency on OSGi LogService.
* It first tries to log to a log service implementation if there is one available and then fallback to System out/err
* in case there is no log service available.
*/
public class Logger
{
public static final int LOG_ERROR = 1;
public static final int LOG_WARNING = 2;
public static final int LOG_INFO = 3;
public static final int LOG_DEBUG = 4;
/**
* Bundle context.
*/
private final BundleContext m_context;
private boolean m_isLogClassPresent;
/**
* Constructor.
*
* @param context bundle context
*/
public Logger(BundleContext context)
{
m_context = context;
try
{
org.osgi.service.log.LogService.class.getName();
m_isLogClassPresent = true;
}
catch (NoClassDefFoundError ex)
{
m_isLogClassPresent = false;
}
}
/**
* @see LogService#log(int, String)
*/
public void log(int level, String message)
{
log(level, message, null);
}
/**
* @see LogService#log(int, String, Throwable)
*/
public void log(int level, String message, Throwable exception)
{
if (!m_isLogClassPresent || !_log(level, message, exception))
{
final PrintStream stream = getStream(level);
stream.println(message);
if (exception != null)
{
exception.printStackTrace(stream);
}
}
}
/**
* Lookup the OSGi LogService and if available use it.
*/
private boolean _log(int level, String message, Throwable exception)
{
try
{
ServiceReference reference = null;
reference = m_context.getServiceReference(LogService.class.getName());
if (reference != null)
{
final LogService logService = (LogService) m_context.getService(reference);
if (logService != null)
{
logService.log(level, message, exception);
m_context.ungetService(reference);
return true;
}
}
}
catch (NoClassDefFoundError e)
{
//ignore
}
return false;
}
/**
* Return the standard print streams to use depending on log level.
*
* @param level log level
* @return print stream corresponding to log level
*/
private PrintStream getStream(int level)
{
switch (level)
{
case LOG_ERROR:
System.err.print("ERROR: ");
return System.err;
case LOG_WARNING:
System.err.print("WARNING: ");
return System.err;
case LOG_INFO:
System.out.print("INFO: ");
return System.out;
case LOG_DEBUG:
System.out.print("DEBUG: ");
return System.out;
default:
System.out.print("UNKNOWN: ");
return System.out;
}
}
}