一.插件简介
插件用于扩展nopCommerce的功能。nopCommerce有几种类型的插件如：支付、税率、配送方式、小部件等（接口如下图），更多插件可以访问。
我们看下后台如何配置管理插件的。
【后台管理】【商城配置】【挂件管理】用于配置小部件，【插件管理】【本地插件】管理本地所有插件
nop自带小部件：Nop.Plugin.Widgets.NivoSlider插件用于主页显示幻灯片，后续我们以此插件为例介绍nop是如何加载小部件的
本文主要介绍的是用于在网站中显示的小部件widgets（实现IWidgetPlugin接口）。
只介绍网站中是如何调用的，后续文章中再介绍如何创建IWidgetPlugin插件。
二.小部件介绍及使用
小部件也可以叫小挂件，继承IWidgetPlugin接口。
是用于在网站中显示的小插件。
自带有：Nop.Plugin.Widgets.NivoSlider插件显示幻灯片。如下图红色区域
我们先看下NivoSlider插件文档结构，每一个插件都有一个Description.txt用于插件的描述。
NivoSlider插件Description.txt内容如下图。
SystemName:系统名称唯一。
SupportedVersions: 该插件支持的nop版本号，nop版本号不对可是在插件列表里不显示的。
FileName:程序集dll文件名，一定要和插件生成的dll文件名一样，否则报错
对比后台理解更直观些
安装、卸载插件在后台管理中心进行管理，这里就不多说了。
安装成功的插件会将系统名称保存在项目文件"~/App_Data/InstalledPlugins.txt"中。
三.小部件调用原理分析
我们看网站是如显示小部件的，还是以NivoSlider插件为例.NivoSlider是在首页显示的，打开首页试图“Home\Index.chtml”
我们发现有很多像@Html.Widget("home_page_top")的节点。
@Html.Widget会调用WidgetController控制器下WidgetsByZone方法从而获取显示内容并输出到页面中
1 public static MvcHtmlString Widget(this HtmlHelper helper, string widgetZone, object additionalData = null, string area = null) 2 { 3 return helper.Action("WidgetsByZone", "Widget", new { widgetZone = widgetZone, additionalData = additionalData, area = area }); 4 } 再来看下小部件中NivoSliderPlugin类，它继承了IWidgetPlugin接口
并实现了IWidgetPlugin接口GetWidgetZones()方法返回显示位置名称集合。
我们发现NivoSlider插件包含了“home_page_top”的位置。
Index.chtml试图中也出现了@Html.Widget("home_page_top")，因此该小部件会在首页中显示。
所以试图中想要使用小部件，使用@Html.Widget("位置名称")就可以了。
ok，知道怎么使用了，我们再看看源码中涉及到哪些相关接口，之间调用关系是怎样的，先上图。
首先WidgetController控制器WidgetsByZone会返回部分视图
1 [ChildActionOnly] 2 public virtual ActionResult WidgetsByZone(string widgetZone, object additionalData = null) 3 { 4 //查找到符合要求的List 5 var model = _widgetModelFactory.GetRenderWidgetModels(widgetZone, additionalData); 6 7 //no data? 8 if (!model.Any()) 9 return Content(""); 10 11 return PartialView(model); 12 } WidgetsByZone.cshtml中代码如下，我们发现这里重新调用了插件中某个action
1 @model List2 @using Nop.Web.Models.Cms; 3 @foreach (var widget in Model) 4 { 5 @Html.Action(widget.ActionName, widget.ControllerName, widget.RouteValues) 6 }
那上边的Action信息又是哪里得到的呢？IWidgetPlugin接口GetDisplayWidgetRoute就是用来返回显示时调用的处理Action信息。
NivoSliderPlugin类实现了GetDisplayWidgetRoute代码如下。
1 ///2 /// 获取显示插件的路由 3 /// 4 /// Widget zone where it's displayed 5 /// Action name 6 /// Controller name 7 /// Route values 8 public void GetDisplayWidgetRoute(string widgetZone, out string actionName, out string controllerName, out RouteValueDictionary routeValues) 9 { 10 actionName = "PublicInfo"; 11 controllerName = "WidgetsNivoSlider"; 12 routeValues = new RouteValueDictionary 13 { 14 {"Namespaces", "Nop.Plugin.Widgets.NivoSlider.Controllers"}, 15 {"area", null}, 16 {"widgetZone", widgetZone} 17 }; 18 }
总结下：WidgetController->WidgetsByZone负责调用显示插件。
而我们开发的小部件需要实现IWidgetPlugin接口GetDisplayWidgetRoute方法告诉上层，我的显示入口是哪个controller 下的action。
下面我们分析下nop是如何找到我们开发的小部件呢？继续看图。
IWidgetModelFactory
GetRenderWidgetModels(widgetZone, additionalData)方法，
传入小部件位置widgetZone（本例中为"home_page_top"）获取List<RenderWidgetModel>
IWidgetService
LoadActiveWidgetsByWidgetZone(widgetZone, _workContext.CurrentCustomer, _storeContext.CurrentStore.Id)
负责返回符合要求的IList<IWidgetPlugin>集合，过滤条件为部件位置，用户，商城。
1 ///2 /// Load active widgets 3 /// 4 /// Widget zone 5 /// Load records allowed only to a specified customer; pass null to ignore ACL permissions 6 /// Load records allowed only in a specified store; pass 0 to load all records 7 ///Widgets 8 public virtual IListLoadActiveWidgetsByWidgetZone(string widgetZone, Customer customer = null, int storeId = 0) 9 { 10 if (String.IsNullOrWhiteSpace(widgetZone)) 11 return new List (); 12 13 return LoadActiveWidgets(customer, storeId) 14 .Where(x => x.GetWidgetZones().Contains(widgetZone, StringComparer.InvariantCultureIgnoreCase)).ToList(); 15 } 16 17 /// 18 /// Load active widgets 19 /// 20 /// Load records allowed only to a specified customer; pass null to ignore ACL permissions 21 /// Load records allowed only in a specified store; pass 0 to load all records 22 ///Widgets 23 public virtual IListLoadActiveWidgets(Customer customer = null, int storeId = 0) 24 { 25 return LoadAllWidgets(customer, storeId) 26 .Where(x => _widgetSettings.ActiveWidgetSystemNames.Contains(x.PluginDescriptor.SystemName, StringComparer.InvariantCultureIgnoreCase)).ToList(); 27 } 28 29 /// 30 /// Load all widgets 31 /// 32 /// Load records allowed only to a specified customer; pass null to ignore ACL permissions 33 /// Load records allowed only in a specified store; pass 0 to load all records 34 ///Widgets 35 public virtual IListLoadAllWidgets(Customer customer = null, int storeId = 0) 36 { 37 return _pluginFinder.GetPlugins (customer: customer, storeId: storeId).ToList(); 38 }
IPluginFinder
_pluginFinder.GetPlugins<IWidgetPlugin>(customer: customer, storeId: storeId).ToList()；
查询继承IWidgetPlugin接口的插件也就是小部件了，这里只返回IWidgetPlugin实现类。
PluginManager
1 using System; 2 using System.Collections.Generic; 3 using System.Configuration; 4 using System.Diagnostics; 5 using System.IO; 6 using System.Linq; 7 using System.Reflection; 8 using System.Threading; 9 using System.Web; 10 using System.Web.Compilation; 11 using Nop.Core.ComponentModel; 12 using Nop.Core.Plugins; 13 14 //Contributor: Umbraco (http://www.umbraco.com). Thanks a lot! 15 //SEE THIS POST for full details of what this does - http://shazwazza.com/post/Developing-a-plugin-framework-in-ASPNET-with-medium-trust.aspx 16 17 [assembly: PreApplicationStartMethod(typeof(PluginManager), "Initialize")] 18 namespace Nop.Core.Plugins 19 { 20 /// 21 /// Sets the application up for the plugin referencing 22 /// 23 public class PluginManager 24 { 25 #region Const 26 27 private const string InstalledPluginsFilePath = "~/App_Data/InstalledPlugins.txt"; 28 private const string PluginsPath = "~/Plugins"; 29 private const string ShadowCopyPath = "~/Plugins/bin"; 30 31 #endregion 32 33 #region Fields 34 35 private static readonly ReaderWriterLockSlim Locker = new ReaderWriterLockSlim(); 36 private static DirectoryInfo _shadowCopyFolder; 37 private static bool _clearShadowDirectoryOnStartup; 38 39 #endregion 40 41 #region Methods 42 43 /// 44 /// Returns a collection of all referenced plugin assemblies that have been shadow copied 45 /// 46 public static IEnumerable ReferencedPlugins { get; set; } 47 48 /// 49 /// Returns a collection of all plugin which are not compatible with the current version 50 /// 51 public static IEnumerable IncompatiblePlugins { get; set; } 52 53 /// 54 /// Initialize 55 /// 56 public static void Initialize() 57 { 58 using (new WriteLockDisposable(Locker)) 59 { 60 // TODO: Add verbose exception handling / raising here since this is happening on app startup and could 61 // prevent app from starting altogether 62 var pluginFolder = new DirectoryInfo(CommonHelper.MapPath(PluginsPath)); 63 _shadowCopyFolder = new DirectoryInfo(CommonHelper.MapPath(ShadowCopyPath)); 64 65 var referencedPlugins = new List (); 66 var incompatiblePlugins = new List (); 67 68 _clearShadowDirectoryOnStartup = !String.IsNullOrEmpty(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]) && 69 Convert.ToBoolean(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]); 70 71 try 72 { 73 var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath()); 74 75 Debug.WriteLine("Creating shadow copy folder and querying for dlls"); 76 //ensure folders are created 77 Directory.CreateDirectory(pluginFolder.FullName); 78 Directory.CreateDirectory(_shadowCopyFolder.FullName); 79 80 //get list of all files in bin 81 var binFiles = _shadowCopyFolder.GetFiles("*", SearchOption.AllDirectories); 82 if (_clearShadowDirectoryOnStartup) 83 { 84 //clear out shadow copied plugins 85 foreach (var f in binFiles) 86 { 87 Debug.WriteLine("Deleting " + f.Name); 88 try 89 { 90 File.Delete(f.FullName); 91 } 92 catch (Exception exc) 93 { 94 Debug.WriteLine("Error deleting file " + f.Name + ". Exception: " + exc); 95 } 96 } 97 } 98 99 //load description files100 foreach (var dfd in GetDescriptionFilesAndDescriptors(pluginFolder))101 {102 var descriptionFile = dfd.Key;103 var pluginDescriptor = dfd.Value;104 105 //ensure that version of plugin is valid106 if (!pluginDescriptor.SupportedVersions.Contains(NopVersion.CurrentVersion, StringComparer.InvariantCultureIgnoreCase))107 {108 incompatiblePlugins.Add(pluginDescriptor.SystemName);109 continue;110 }111 112 //some validation113 if (String.IsNullOrWhiteSpace(pluginDescriptor.SystemName))114 throw new Exception(string.Format("A plugin '{0}' has no system name. Try assigning the plugin a unique name and recompiling.", descriptionFile.FullName));115 if (referencedPlugins.Contains(pluginDescriptor))116 throw new Exception(string.Format("A plugin with '{0}' system name is already defined", pluginDescriptor.SystemName));117 118 //set 'Installed' property119 pluginDescriptor.Installed = installedPluginSystemNames120 .FirstOrDefault(x => x.Equals(pluginDescriptor.SystemName, StringComparison.InvariantCultureIgnoreCase)) != null;121 122 try123 {124 if (descriptionFile.Directory == null)125 throw new Exception(string.Format("Directory cannot be resolved for '{0}' description file", descriptionFile.Name));126 //get list of all DLLs in plugins (not in bin!)127 var pluginFiles = descriptionFile.Directory.GetFiles("*.dll", SearchOption.AllDirectories)128 //just make sure we're not registering shadow copied plugins129 .Where(x => !binFiles.Select(q => q.FullName).Contains(x.FullName))130 .Where(x => IsPackagePluginFolder(x.Directory))131 .ToList();132 133 //other plugin description info134 var mainPluginFile = pluginFiles135 .FirstOrDefault(x => x.Name.Equals(pluginDescriptor.PluginFileName, StringComparison.InvariantCultureIgnoreCase));136 pluginDescriptor.OriginalAssemblyFile = mainPluginFile;137 138 //shadow copy main plugin file139 pluginDescriptor.ReferencedAssembly = PerformFileDeploy(mainPluginFile);140 141 //load all other referenced assemblies now142 foreach (var plugin in pluginFiles143 .Where(x => !x.Name.Equals(mainPluginFile.Name, StringComparison.InvariantCultureIgnoreCase))144 .Where(x => !IsAlreadyLoaded(x)))145 PerformFileDeploy(plugin);146 147 //init plugin type (only one plugin per assembly is allowed)148 foreach (var t in pluginDescriptor.ReferencedAssembly.GetTypes())149 if (typeof(IPlugin).IsAssignableFrom(t))150 if (!t.IsInterface)151 if (t.IsClass && !t.IsAbstract)152 {153 pluginDescriptor.PluginType = t;154 break;155 }156 157 referencedPlugins.Add(pluginDescriptor);158 }159 catch (ReflectionTypeLoadException ex)160 {161 //add a plugin name. this way we can easily identify a problematic plugin162 var msg = string.Format("Plugin '{0}'. ", pluginDescriptor.FriendlyName);163 foreach (var e in ex.LoaderExceptions)164 msg += e.Message + Environment.NewLine;165 166 var fail = new Exception(msg, ex);167 throw fail;168 }169 catch (Exception ex)170 {171 //add a plugin name. this way we can easily identify a problematic plugin172 var msg = string.Format("Plugin '{0}'. {1}", pluginDescriptor.FriendlyName, ex.Message);173 174 var fail = new Exception(msg, ex);175 throw fail;176 }177 }178 }179 catch (Exception ex)180 {181 var msg = string.Empty;182 for (var e = ex; e != null; e = e.InnerException)183 msg += e.Message + Environment.NewLine;184 185 var fail = new Exception(msg, ex);186 throw fail;187 }188 189 190 ReferencedPlugins = referencedPlugins;191 IncompatiblePlugins = incompatiblePlugins;192 193 }194 }195 196 /// 197 /// Mark plugin as installed198 /// 199 /// Plugin system name200 public static void MarkPluginAsInstalled(string systemName)201 {202 if (String.IsNullOrEmpty(systemName))203 throw new ArgumentNullException("systemName");204 205 var filePath = CommonHelper.MapPath(InstalledPluginsFilePath);206 if (!File.Exists(filePath))207 using (File.Create(filePath))208 {209 //we use 'using' to close the file after it's created210 }211 212 213 var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());214 bool alreadyMarkedAsInstalled = installedPluginSystemNames215 .FirstOrDefault(x => x.Equals(systemName, StringComparison.InvariantCultureIgnoreCase)) != null;216 if (!alreadyMarkedAsInstalled)217 installedPluginSystemNames.Add(systemName);218 PluginFileParser.SaveInstalledPluginsFile(installedPluginSystemNames,filePath);219 }220 221 /// 222 /// Mark plugin as uninstalled223 /// 224 /// Plugin system name225 public static void MarkPluginAsUninstalled(string systemName)226 {227 if (String.IsNullOrEmpty(systemName))228 throw new ArgumentNullException("systemName");229 230 var filePath = CommonHelper.MapPath(InstalledPluginsFilePath);231 if (!File.Exists(filePath))232 using (File.Create(filePath))233 {234 //we use 'using' to close the file after it's created235 }236 237 238 var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());239 bool alreadyMarkedAsInstalled = installedPluginSystemNames240 .FirstOrDefault(x => x.Equals(systemName, StringComparison.InvariantCultureIgnoreCase)) != null;241 if (alreadyMarkedAsInstalled)242 installedPluginSystemNames.Remove(systemName);243 PluginFileParser.SaveInstalledPluginsFile(installedPluginSystemNames,filePath);244 }245 246 /// 247 /// Mark plugin as uninstalled248 /// 249 public static void MarkAllPluginsAsUninstalled()250 {251 var filePath = CommonHelper.MapPath(InstalledPluginsFilePath);252 if (File.Exists(filePath))253 File.Delete(filePath);254 }255 256 #endregion257 258 #region Utilities259 260 /// 261 /// Get description files262 /// 263 /// Plugin directory info264 /// Original and parsed description files 265 private static IEnumerable > GetDescriptionFilesAndDescriptors(DirectoryInfo pluginFolder)266 {267 if (pluginFolder == null)268 throw new ArgumentNullException("pluginFolder");269 270 //create list ( )271 var result = new List >();272 //add display order and path to list273 foreach (var descriptionFile in pluginFolder.GetFiles("Description.txt", SearchOption.AllDirectories))274 {275 if (!IsPackagePluginFolder(descriptionFile.Directory))276 continue;277 278 //parse file279 var pluginDescriptor = PluginFileParser.ParsePluginDescriptionFile(descriptionFile.FullName);280 281 //populate list282 result.Add(new KeyValuePair (descriptionFile, pluginDescriptor));283 }284 285 //sort list by display order. NOTE: Lowest DisplayOrder will be first i.e 0 , 1, 1, 1, 5, 10286 //it's required: http://www.nopcommerce.com/boards/t/17455/load-plugins-based-on-their-displayorder-on-startup.aspx287 result.Sort((firstPair, nextPair) => firstPair.Value.DisplayOrder.CompareTo(nextPair.Value.DisplayOrder));288 return result;289 }290 291 /// 292 /// Indicates whether assembly file is already loaded293 /// 294 /// File info295 /// Result 296 private static bool IsAlreadyLoaded(FileInfo fileInfo)297 {298 //compare full assembly name299 //var fileAssemblyName = AssemblyName.GetAssemblyName(fileInfo.FullName);300 //foreach (var a in AppDomain.CurrentDomain.GetAssemblies())301 //{ 302 // if (a.FullName.Equals(fileAssemblyName.FullName, StringComparison.InvariantCultureIgnoreCase))303 // return true;304 //}305 //return false;306 307 //do not compare the full assembly name, just filename308 try309 {310 string fileNameWithoutExt = Path.GetFileNameWithoutExtension(fileInfo.FullName);311 if (fileNameWithoutExt == null)312 throw new Exception(string.Format("Cannot get file extension for {0}", fileInfo.Name));313 foreach (var a in AppDomain.CurrentDomain.GetAssemblies())314 {315 string assemblyName = a.FullName.Split(new[] { ',' }).FirstOrDefault();316 if (fileNameWithoutExt.Equals(assemblyName, StringComparison.InvariantCultureIgnoreCase))317 return true;318 }319 }320 catch (Exception exc)321 {322 Debug.WriteLine("Cannot validate whether an assembly is already loaded. " + exc);323 }324 return false;325 }326 327 /// 328 /// Perform file deply329 /// 330 /// Plugin file info331 /// Assembly 332 private static Assembly PerformFileDeploy(FileInfo plug)333 {334 if (plug.Directory == null || plug.Directory.Parent == null)335 throw new InvalidOperationException("The plugin directory for the " + plug.Name + " file exists in a folder outside of the allowed nopCommerce folder hierarchy");336 337 FileInfo shadowCopiedPlug;338 339 if (CommonHelper.GetTrustLevel() != AspNetHostingPermissionLevel.Unrestricted)340 {341 //all plugins will need to be copied to ~/Plugins/bin/342 //this is absolutely required because all of this relies on probingPaths being set statically in the web.config343 344 //were running in med trust, so copy to custom bin folder345 var shadowCopyPlugFolder = Directory.CreateDirectory(_shadowCopyFolder.FullName);346 shadowCopiedPlug = InitializeMediumTrust(plug, shadowCopyPlugFolder);347 }348 else349 {350 var directory = AppDomain.CurrentDomain.DynamicDirectory;351 Debug.WriteLine(plug.FullName + " to " + directory);352 //were running in full trust so copy to standard dynamic folder353 shadowCopiedPlug = InitializeFullTrust(plug, new DirectoryInfo(directory));354 }355 356 //we can now register the plugin definition357 var shadowCopiedAssembly = Assembly.Load(AssemblyName.GetAssemblyName(shadowCopiedPlug.FullName));358 359 //add the reference to the build manager360 Debug.WriteLine("Adding to BuildManager: '{0}'", shadowCopiedAssembly.FullName);361 BuildManager.AddReferencedAssembly(shadowCopiedAssembly);362 363 return shadowCopiedAssembly;364 }365 366 /// 367 /// Used to initialize plugins when running in Full Trust368 /// 369 /// 370 /// 371 /// 401 /// Used to initialize plugins when running in Medium Trust402 /// 403 /// 404 /// 405 /// 462 /// Determines if the folder is a bin plugin folder for a package463 /// 464 /// 465 /// 475 /// Gets the full path of InstalledPlugins.txt file476 /// 477 /// PluginManager.ReferencedPlugins获取到所有的插件。
PluginManager类用于管理插件，我们发现[assembly: PreApplicationStartMethod(typeof(PluginManager), "Initialize")]表示应用程序启动就调用PluginManager类下边的Initialize方法进行初始化。初始化过程中会把所有插件保存到ReferencedPlugins变量中。
经过上边一层层的过滤查找，终于找到了符合要求的插件了并保存在IList<IWidgetPlugin>集合中。最后经过IWidgetModelFactory接口GetRenderWidgetModels(widgetZone, additionalData)方法处理保存为List<RenderWidgetModel>最后为WidgetsByZone试图使用。
ps： 调用关系描述的不是很清晰，请见谅，大家还是看图，结合代码理解吧。
四.总结
1.nop支持各种插件，不同插件继承接口不一样
2.小部件继承IWidgetPlugin，用于在网页中显示。
3.IWidgetPlugin接口 IList<string> GetWidgetZones()返回显示部件的位置名称集合。GetDisplayWidgetRoute方法返回显示插件时的路由。
4.网站视图中用@Html.Widget("位置名称")来显示插件。”位置名称”包含在插件GetWidgetZones()返回的集合中。
文中有错误的理解和不正确的观点请指正、留言、一起交流共同进步。
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