src/log4net/Util/PatternStringConverters/EnvironmentPatternConverter.cs

#region Apache License
//
// 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.
//
#endregion

// .NET Compact Framework 1.0 has no support for Environment.GetEnvironmentVariable()
#if !NETCF

using System;
using System.Text;
using System.IO;

using log4net.Util;
using log4net.DateFormatter;
using log4net.Core;

namespace log4net.Util.PatternStringConverters
{
	/// <summary>
	/// Write an environment variable to the output
	/// </summary>
	/// <remarks>
	/// <para>
	/// Write an environment variable to the output writer.
	/// The value of the <see cref="log4net.Util.PatternConverter.Option"/> determines 
	/// the name of the variable to output.
	/// </para>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	internal sealed class EnvironmentPatternConverter : PatternConverter
	{
		/// <summary>
		/// Write an environment variable to the output
		/// </summary>
		/// <param name="writer">the writer to write to</param>
		/// <param name="state">null, state is not set</param>
		/// <remarks>
		/// <para>
		/// Writes the environment variable to the output <paramref name="writer"/>.
		/// The name of the environment variable to output must be set
		/// using the <see cref="log4net.Util.PatternConverter.Option"/>
		/// property.
		/// </para>
		/// </remarks>
		override protected void Convert(TextWriter writer, object state) 
		{
			try 
			{
				if (this.Option != null && this.Option.Length > 0)
				{
					// Lookup the environment variable
					string envValue = Environment.GetEnvironmentVariable(this.Option);

#if NET_2_0					
                    // If we didn't see it for the process, try a user level variable.
				    if (envValue == null)
				    {
				        envValue = Environment.GetEnvironmentVariable(this.Option, EnvironmentVariableTarget.User);
				    }

                    // If we still didn't find it, try a system level one.
				    if (envValue == null)
				    {
				        envValue = Environment.GetEnvironmentVariable(this.Option, EnvironmentVariableTarget.Machine);
				    }
#endif					

					if (envValue != null && envValue.Length > 0)
					{
						writer.Write(envValue);
					}
				}
			}
			catch(System.Security.SecurityException secEx)
			{
				// This security exception will occur if the caller does not have 
				// unrestricted environment permission. If this occurs the expansion 
				// will be skipped with the following warning message.
				LogLog.Debug(declaringType, "Security exception while trying to expand environment variables. Error Ignored. No Expansion.", secEx);
			}
			catch (Exception ex) 
			{
				LogLog.Error(declaringType, "Error occurred while converting environment variable.", ex);
			}
		}

	    #region Private Static Fields

	    /// <summary>
	    /// The fully qualified type of the EnvironmentPatternConverter class.
	    /// </summary>
	    /// <remarks>
	    /// Used by the internal logger to record the Type of the
	    /// log message.
	    /// </remarks>
	    private readonly static Type declaringType = typeof(EnvironmentPatternConverter);

	    #endregion Private Static Fields
	}
}

#endif // !NETCF