appenderattachedimpl.cs

详细讲述了数据库编程

#region Copyright & License
//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed 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

using System;

using log4net.Core;
using log4net.Appender;

namespace log4net.Util
{
	/// <summary>
	/// A straightforward implementation of the <see cref="IAppenderAttachable"/> interface.
	/// </summary>
	/// <remarks>
	/// <para>
	/// This is the default implementation of the <see cref="IAppenderAttachable"/>
	/// interface. Implementors of the <see cref="IAppenderAttachable"/> interface
	/// should aggregate an instance of this type.
	/// </para>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	/// <author>Gert Driesen</author>
	public class AppenderAttachedImpl : IAppenderAttachable
	{
		#region Public Instance Constructors

		/// <summary>
		/// Constructor
		/// </summary>
		/// <remarks>
		/// <para>
		/// Initializes a new instance of the <see cref="AppenderAttachedImpl"/> class.
		/// </para>
		/// </remarks>
		public AppenderAttachedImpl()
		{
		}

		#endregion Public Instance Constructors

		#region Public Instance Methods

		/// <summary>
		/// Append on on all attached appenders.
		/// </summary>
		/// <param name="loggingEvent">The event being logged.</param>
		/// <returns>The number of appenders called.</returns>
		/// <remarks>
		/// <para>
		/// Calls the <see cref="IAppender.DoAppend" /> method on all 
		/// attached appenders.
		/// </para>
		/// </remarks>
		public int AppendLoopOnAppenders(LoggingEvent loggingEvent) 
		{
			if (loggingEvent == null)
			{
				throw new ArgumentNullException("loggingEvent");
			}

			// m_appenderList is null when empty
			if (m_appenderList == null) 
			{
				return 0;
			}

			if (m_appenderArray == null)
			{
				m_appenderArray = m_appenderList.ToArray();
			}

			foreach(IAppender appender in m_appenderArray)
			{
				try
				{
					appender.DoAppend(loggingEvent);
				}
				catch(Exception ex)
				{
					LogLog.Error("AppenderAttachedImpl: Failed to append to appender [" + appender.Name + "]", ex);
				}
			}
			return m_appenderList.Count;
		}

		/// <summary>
		/// Append on on all attached appenders.
		/// </summary>
		/// <param name="loggingEvents">The array of events being logged.</param>
		/// <returns>The number of appenders called.</returns>
		/// <remarks>
		/// <para>
		/// Calls the <see cref="IAppender.DoAppend" /> method on all 
		/// attached appenders.
		/// </para>
		/// </remarks>
		public int AppendLoopOnAppenders(LoggingEvent[] loggingEvents) 
		{
			if (loggingEvents == null)
			{
				throw new ArgumentNullException("loggingEvents");
			}
			if (loggingEvents.Length == 0)
			{
				throw new ArgumentException("loggingEvents array must not be empty", "loggingEvents");
			}
			if (loggingEvents.Length == 1)
			{
				// Fall back to single event path
				return AppendLoopOnAppenders(loggingEvents[0]);
			}

			// m_appenderList is null when empty
			if (m_appenderList == null) 
			{
				return 0;
			}

			if (m_appenderArray == null)
			{
				m_appenderArray = m_appenderList.ToArray();
			}

			foreach(IAppender appender in m_appenderArray)
			{
				try
				{
					CallAppend(appender, loggingEvents);
				}
				catch(Exception ex)
				{
					LogLog.Error("AppenderAttachedImpl: Failed to append to appender [" + appender.Name + "]", ex);
				}
			}
			return m_appenderList.Count;
		}

		#endregion Public Instance Methods

		/// <summary>
		/// Calls the DoAppende method on the <see cref="IAppender"/> with 
		/// the <see cref="LoggingEvent"/> objects supplied.
		/// </summary>
		/// <param name="appender">The appender</param>
		/// <param name="loggingEvents">The events</param>
		/// <remarks>
		/// <para>
		/// If the <paramref name="appender" /> supports the <see cref="IBulkAppender"/>
		/// interface then the <paramref name="loggingEvents" /> will be passed 
		/// through using that interface. Otherwise the <see cref="LoggingEvent"/>
		/// objects in the array will be passed one at a time.
		/// </para>
		/// </remarks>
		private static void CallAppend(IAppender appender, LoggingEvent[] loggingEvents)
		{
			IBulkAppender bulkAppender = appender as IBulkAppender;
			if (bulkAppender != null)
			{
				bulkAppender.DoAppend(loggingEvents);
			}
			else
			{
				foreach(LoggingEvent loggingEvent in loggingEvents)
				{
					appender.DoAppend(loggingEvent);
				}
			}
		}

		#region Implementation of IAppenderAttachable

		/// <summary>
		/// Attaches an appender.
		/// </summary>
		/// <param name="newAppender">The appender to add.</param>
		/// <remarks>
		/// <para>
		/// If the appender is already in the list it won't be added again.
		/// </para>
		/// </remarks>
		public void AddAppender(IAppender newAppender) 
		{
			// Null values for newAppender parameter are strictly forbidden.
			if (newAppender == null)
			{
				throw new ArgumentNullException("newAppender");
			}
	
			m_appenderArray = null;
			if (m_appenderList == null) 
			{
				m_appenderList = new AppenderCollection(1);
			}
			if (!m_appenderList.Contains(newAppender))
			{
				m_appenderList.Add(newAppender);
			}
		}

		/// <summary>
		/// Gets all attached appenders.
		/// </summary>
		/// <returns>
		/// A collection of attached appenders, or <c>null</c> if there
		/// are no attached appenders.
		/// </returns>
		/// <remarks>
		/// <para>
		/// The read only collection of all currently attached appenders.
		/// </para>
		/// </remarks>
		public AppenderCollection Appenders 
		{
			get
			{
				if (m_appenderList == null)
				{
					// We must always return a valid collection
					return AppenderCollection.EmptyCollection;
				}
				else 
				{
					return AppenderCollection.ReadOnly(m_appenderList);
				}
			}
		}

		/// <summary>
		/// Gets an attached appender with the specified name.
		/// </summary>
		/// <param name="name">The name of the appender to get.</param>
		/// <returns>
		/// The appender with the name specified, or <c>null</c> if no appender with the
		/// specified name is found.
		/// </returns>
		/// <remarks>
		/// <para>
		/// Lookup an attached appender by name.
		/// </para>
		/// </remarks>
		public IAppender GetAppender(string name) 
		{
			if (m_appenderList != null && name != null)
			{
				foreach(IAppender appender in m_appenderList)
				{
					if (name == appender.Name)
					{
						return appender;
					}
				}
			}
			return null;   
		}

		/// <summary>
		/// Removes all attached appenders.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Removes and closes all attached appenders
		/// </para>
		/// </remarks>
		public void RemoveAllAppenders() 
		{
			if (m_appenderList != null) 
			{
				foreach(IAppender appender in m_appenderList)
				{
					try
					{
						appender.Close();
					}
					catch(Exception ex)
					{
						LogLog.Error("AppenderAttachedImpl: Failed to Close appender ["+appender.Name+"]", ex);
					}
				}
				m_appenderList = null;	  
				m_appenderArray = null;
			}
		}

		/// <summary>
		/// Removes the specified appender from the list of attached appenders.
		/// </summary>
		/// <param name="appender">The appender to remove.</param>
		/// <returns>The appender removed from the list</returns>
		/// <remarks>
		/// <para>
		/// The appender removed is not closed.
		/// If you are discarding the appender you must call
		/// <see cref="IAppender.Close"/> on the appender removed.
		/// </para>
		/// </remarks>
		public IAppender RemoveAppender(IAppender appender) 
		{
			if (appender != null && m_appenderList != null) 
			{
				m_appenderList.Remove(appender);
				if (m_appenderList.Count == 0)
				{
					m_appenderList = null;
				}
				m_appenderArray = null;
			}
			return appender;
		}

		/// <summary>
		/// Removes the appender with the specified name from the list of appenders.
		/// </summary>
		/// <param name="name">The name of the appender to remove.</param>
		/// <returns>The appender removed from the list</returns>
		/// <remarks>
		/// <para>
		/// The appender removed is not closed.
		/// If you are discarding the appender you must call
		/// <see cref="IAppender.Close"/> on the appender removed.
		/// </para>
		/// </remarks>
		public IAppender RemoveAppender(string name) 
		{
			return RemoveAppender(GetAppender(name));
		}

		#endregion

		#region Private Instance Fields

		/// <summary>
		/// List of appenders
		/// </summary>
		private AppenderCollection m_appenderList;

		/// <summary>
		/// Array of appenders, used to cache the m_appenderList
		/// </summary>
		private IAppender[] m_appenderArray;

		#endregion Private Instance Fields
	}
}