pluginattribute.cs

精通SQL Server2005项目开发

#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

// .NET Compact Framework 1.0 has no support for reading assembly attributes
#if !NETCF

using System;
using System.Globalization;
using System.Reflection;

using log4net.Core;
using log4net.Util;
using log4net.Plugin;

namespace log4net.Config
{
	/// <summary>
	/// Assembly level attribute that specifies a plugin to attach to 
	/// the repository.
	/// </summary>
	/// <remarks>
	/// <para>
	/// Specifies the type of a plugin to create and attach to the
	/// assembly's repository. The plugin type must implement the
	/// <see cref="IPlugin"/> interface.
	/// </para>
	/// </remarks>
	/// <author>Nicko Cadell</author>
	/// <author>Gert Driesen</author>
	[AttributeUsage(AttributeTargets.Assembly,AllowMultiple=true)]
	[Serializable]
	public sealed class PluginAttribute : Attribute, IPluginFactory
	{
		#region Public Instance Constructors

		/// <summary>
		/// Initializes a new instance of the <see cref="PluginAttribute" /> class
		/// with the specified type.
		/// </summary>
		/// <param name="typeName">The type name of plugin to create.</param>
		/// <remarks>
		/// <para>
		/// Create the attribute with the plugin type specified.
		/// </para>
		/// <para>
		/// Where possible use the constructor that takes a <see cref="System.Type"/>.
		/// </para>
		/// </remarks>
		public PluginAttribute(string typeName)
		{
			m_typeName = typeName;
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="PluginAttribute" /> class
		/// with the specified type.
		/// </summary>
		/// <param name="type">The type of plugin to create.</param>
		/// <remarks>
		/// <para>
		/// Create the attribute with the plugin type specified.
		/// </para>
		/// </remarks>
		public PluginAttribute(Type type)
		{
			m_type = type;
		}

		#endregion Public Instance Constructors

		#region Public Instance Properties

		/// <summary>
		/// Gets or sets the type for the plugin.
		/// </summary>
		/// <value>
		/// The type for the plugin.
		/// </value>
		/// <remarks>
		/// <para>
		/// The type for the plugin.
		/// </para>
		/// </remarks>
		public Type Type
		{
			get { return m_type; }
			set { m_type = value ; }
		}

		/// <summary>
		/// Gets or sets the type name for the plugin.
		/// </summary>
		/// <value>
		/// The type name for the plugin.
		/// </value>
		/// <remarks>
		/// <para>
		/// The type name for the plugin.
		/// </para>
		/// <para>
		/// Where possible use the <see cref="Type"/> property instead.
		/// </para>
		/// </remarks>
		public string TypeName
		{
			get { return m_typeName; }
			set { m_typeName = value ; }
		}

		#endregion Public Instance Properties

		#region Implementation of IPluginFactory

		/// <summary>
		/// Creates the plugin object defined by this attribute.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Creates the instance of the <see cref="IPlugin"/> object as 
		/// specified by this attribute.
		/// </para>
		/// </remarks>
		/// <returns>The plugin object.</returns>
		public IPlugin CreatePlugin()
		{
			Type pluginType = m_type;
			if (m_type == null)
			{
				// Get the plugin object type from the string type name
				pluginType = SystemInfo.GetTypeFromString(m_typeName, true, true);
			}

			// Check that the type is a plugin
			if (!(typeof(IPlugin).IsAssignableFrom(pluginType)))
			{
				throw new LogException("Plugin type [" + pluginType.FullName + "] does not implement the log4net.IPlugin interface");
			}

			// Create an instance of the plugin using the default constructor
			IPlugin plugin = (IPlugin)Activator.CreateInstance(pluginType);

			return plugin;
		}

		#endregion Implementation of IPluginFactory

		#region Override implementation of Object

		/// <summary>
		/// Returns a representation of the properties of this object.
		/// </summary>
		/// <remarks>
		/// <para>
		/// Overrides base class <see cref="Object.ToString()" /> method to 
		/// return a representation of the properties of this object.
		/// </para>
		/// </remarks>
		/// <returns>A representation of the properties of this object</returns>
		override public string ToString()
		{
			if (m_type != null)
			{
				return "PluginAttribute[Type=" + m_type.FullName + "]";
			}
			return "PluginAttribute[Type=" + m_typeName + "]";
		}

		#endregion Override implementation of Object

		#region Private Instance Fields

		private string m_typeName = null;
		private Type m_type = null;

		#endregion Private Instance Fields
	}
}

#endif // !NETCF