defaultrepositoryselector.cs

详细讲述了数据库编程

					if (readAssemblyAttributes)
					{
						// Get the repository and type from the assembly attributes
						GetInfoForAssembly(repositoryAssembly, ref actualRepositoryName, ref actualRepositoryType);
					}

					LogLog.Debug("DefaultRepositorySelector: Assembly [" + repositoryAssembly + "] using repository [" + actualRepositoryName + "] and repository type [" + actualRepositoryType + "]");

					// Lookup the repository in the map (as this may already be defined)
					rep = m_name2repositoryMap[actualRepositoryName] as ILoggerRepository;
					if (rep == null)
					{
						// Create the repository
						rep = CreateRepository(actualRepositoryName, actualRepositoryType);

						if (readAssemblyAttributes)
						{
							try
							{
								// Look for aliasing attributes
								LoadAliases(repositoryAssembly, rep);

								// Look for plugins defined on the assembly
								LoadPlugins(repositoryAssembly, rep);

								// Configure the repository using the assembly attributes
								ConfigureRepository(repositoryAssembly, rep);
							}
							catch (Exception ex)
							{
								LogLog.Error("DefaultRepositorySelector: Failed to configure repository [" + actualRepositoryName + "] from assembly attributes.", ex);
							}
						}
					}
					else
					{
						LogLog.Debug("DefaultRepositorySelector: repository [" + actualRepositoryName + "] already exists, using repository type [" + rep.GetType().FullName + "]");

						if (readAssemblyAttributes)
						{
							try
							{
								// Look for plugins defined on the assembly
								LoadPlugins(repositoryAssembly, rep);
							}
							catch (Exception ex)
							{
								LogLog.Error("DefaultRepositorySelector: Failed to configure repository [" + actualRepositoryName + "] from assembly attributes.", ex);
							}
						}
					}
					m_assembly2repositoryMap[repositoryAssembly] = rep;
				}
				return rep;
			}
		}

		/// <summary>
		/// Creates a new repository for the specified repository.
		/// </summary>
		/// <param name="repositoryName">The repository to associate with the <see cref="ILoggerRepository"/>.</param>
		/// <param name="repositoryType">The type of repository to create, must implement <see cref="ILoggerRepository"/>.
		/// If this param is <see langword="null" /> then the default repository type is used.</param>
		/// <returns>The new repository.</returns>
		/// <remarks>
		/// <para>
		/// The <see cref="ILoggerRepository"/> created will be associated with the repository
		/// specified such that a call to <see cref="GetRepository(string)"/> with the
		/// same repository specified will return the same repository instance.
		/// </para>
		/// </remarks>
		/// <exception cref="ArgumentNullException"><paramref name="repositoryName"/> is <see langword="null" />.</exception>
		/// <exception cref="LogException"><paramref name="repositoryName"/> already exists.</exception>
		public ILoggerRepository CreateRepository(string repositoryName, Type repositoryType)
		{
			if (repositoryName == null)
			{
				throw new ArgumentNullException("repositoryName");
			}

			// If the type is not set then use the default type
			if (repositoryType == null)
			{
				repositoryType = m_defaultRepositoryType;
			}

			lock(this)
			{
				ILoggerRepository rep = null;

				// First check that the repository does not exist
				rep = m_name2repositoryMap[repositoryName] as ILoggerRepository;
				if (rep != null)
				{
					throw new LogException("Repository [" + repositoryName + "] is already defined. Repositories cannot be redefined.");
				}
				else
				{
					// Lookup an alias before trying to create the new repository
					ILoggerRepository aliasedRepository = m_alias2repositoryMap[repositoryName] as ILoggerRepository;
					if (aliasedRepository != null)
					{
						// Found an alias

						// Check repository type
						if (aliasedRepository.GetType() == repositoryType)
						{
							// Repository type is compatible
							LogLog.Debug("DefaultRepositorySelector: Aliasing repository [" + repositoryName + "] to existing repository [" + aliasedRepository.Name + "]");
							rep = aliasedRepository;

							// Store in map
							m_name2repositoryMap[repositoryName] = rep;
						}
						else
						{
							// Invalid repository type for alias
							LogLog.Error("DefaultRepositorySelector: Failed to alias repository [" + repositoryName + "] to existing repository ["+aliasedRepository.Name+"]. Requested repository type ["+repositoryType.FullName+"] is not compatible with existing type [" + aliasedRepository.GetType().FullName + "]");

							// We now drop through to create the repository without aliasing
						}
					}

					// If we could not find an alias
					if (rep == null)
					{
						LogLog.Debug("DefaultRepositorySelector: Creating repository [" + repositoryName + "] using type [" + repositoryType + "]");

						// Call the no arg constructor for the repositoryType
						rep = (ILoggerRepository)Activator.CreateInstance(repositoryType);

						// Set the name of the repository
						rep.Name = repositoryName;

						// Store in map
						m_name2repositoryMap[repositoryName] = rep;

						// Notify listeners that the repository has been created
						OnLoggerRepositoryCreatedEvent(rep);
					}
				}

				return rep;
			}
		}

		/// <summary>
		/// Test if a named repository exists
		/// </summary>
		/// <param name="repositoryName">the named repository to check</param>
		/// <returns><c>true</c> if the repository exists</returns>
		/// <remarks>
		/// <para>
		/// Test if a named repository exists. Use <see cref="CreateRepository(string, Type)"/>
		/// to create a new repository and <see cref="GetRepository(string)"/> to retrieve 
		/// a repository.
		/// </para>
		/// </remarks>
		public bool ExistsRepository(string repositoryName)
		{
			lock(this)
			{
				return m_name2repositoryMap.ContainsKey(repositoryName);
			}
		}

		/// <summary>
		/// Gets a list of <see cref="ILoggerRepository"/> objects
		/// </summary>
		/// <returns>an array of all known <see cref="ILoggerRepository"/> objects</returns>
		/// <remarks>
		/// <para>
		/// Gets an array of all of the repositories created by this selector.
		/// </para>
		/// </remarks>
		public ILoggerRepository[] GetAllRepositories()
		{
			lock(this)
			{
				ICollection reps = m_name2repositoryMap.Values;
				ILoggerRepository[] all = new ILoggerRepository[reps.Count];
				reps.CopyTo(all, 0);
				return all;
			}
		}

		#endregion Implementation of IRepositorySelector

		#region Public Instance Methods

		/// <summary>
		/// Aliases a repository to an existing repository.
		/// </summary>
		/// <param name="repositoryAlias">The repository to alias.</param>
		/// <param name="repositoryTarget">The repository that the repository is aliased to.</param>
		/// <remarks>
		/// <para>
		/// The repository specified will be aliased to the repository when created. 
		/// The repository must not already exist.
		/// </para>
		/// <para>
		/// When the repository is created it must utilize the same repository type as 
		/// the repository it is aliased to, otherwise the aliasing will fail.
		/// </para>
		/// </remarks>
		/// <exception cref="ArgumentNullException">
		///	<para><paramref name="repositoryAlias" /> is <see langword="null" />.</para>
		///	<para>-or-</para>
		///	<para><paramref name="repositoryTarget" /> is <see langword="null" />.</para>
		/// </exception>
		public void AliasRepository(string repositoryAlias, ILoggerRepository repositoryTarget) 
		{
			if (repositoryAlias == null) 
			{
				throw new ArgumentNullException("repositoryAlias");
			}
			if (repositoryTarget == null) 
			{
				throw new ArgumentNullException("repositoryTarget");
			}

			lock(this) 
			{
				// Check if the alias is already set
				if (m_alias2repositoryMap.Contains(repositoryAlias)) 
				{
					// Check if this is a duplicate of the current alias
					if (repositoryTarget != ((ILoggerRepository)m_alias2repositoryMap[repositoryAlias])) 
					{
						// Cannot redefine existing alias
						throw new InvalidOperationException("Repository [" + repositoryAlias + "] is already aliased to repository [" + ((ILoggerRepository)m_alias2repositoryMap[repositoryAlias]).Name + "]. Aliases cannot be redefined.");
					}
				}
					// Check if the alias is already mapped to a repository
				else if (m_name2repositoryMap.Contains(repositoryAlias)) 
				{
					// Check if this is a duplicate of the current mapping
					if ( repositoryTarget != ((ILoggerRepository)m_name2repositoryMap[repositoryAlias]) ) 
					{
						// Cannot define alias for already mapped repository
						throw new InvalidOperationException("Repository [" + repositoryAlias + "] already exists and cannot be aliased to repository [" + repositoryTarget.Name + "].");
					}
				}
				else 
				{
					// Set the alias
					m_alias2repositoryMap[repositoryAlias] = repositoryTarget;
				}
			}
		}

		#endregion Public Instance Methods

		#region Protected Instance Methods

		/// <summary>
		/// Notifies the registered listeners that the repository has been created.
		/// </summary>
		/// <param name="repository">The repository that has been created.</param>
		/// <remarks>
		/// <para>
		/// Raises the <see cref="LoggerRepositoryCreatedEvent"/> event.
		/// </para>
		/// </remarks>
		protected virtual void OnLoggerRepositoryCreatedEvent(ILoggerRepository repository) 
		{
			LoggerRepositoryCreationEventHandler handler = m_loggerRepositoryCreatedEvent;
			if (handler != null) 
			{
				handler(this, new LoggerRepositoryCreationEventArgs(repository));
			}
		}

		#endregion Protected Instance Methods

		#region Private Instance Methods

		/// <summary>