概述
NopCommerce源码架构详解-自定义系统启动时执行任务Task相关源码分析。
内容
看过我之前写的AutoMapper在nop中的运用：NopCommerce源码架构详解-AutoMapper对象关联映射相关源码分析，对于Nop的任务Task并不陌生，因为之前就提到过IStartupTask接口和AutoMapperStartupTask。今天单独写篇文章来分析一下Nop中的自定义系统启动时执行任务Task相关源码。
相关功能主要用到的类或接口：
1、IStartupTask
2、AutoMapperStartupTask、EfStartUpTask
3、IEngine
4、NopEngine
5、EngineContext
6、Global.asax
1、IStartupTask
namespace Nop.Core.Infrastructure
{
/// <summary>
/// Interface which should be implemented by tasks run on startup
/// </summary>
public interface IStartupTask
{
/// <summary>
/// Execute task
/// </summary>
void Execute();
/// <summary>
/// Order
/// </summary>
int Order { get; }
}
}
IStartupTask接口是所有的启动任务的抽象接口，所有的自定义启动任务都要实现这个接口。
2、AutoMapperStartupTask、EfStartUpTask
AutoMapperStartupTask和EfStartUpTask接口IStartupTask的真正实现，所有的逻辑都可以写在里面。如EfStartUpTask.cs：
using Nop.Core;
using Nop.Core.Data;
using Nop.Core.Infrastructure;
namespace Nop.Data
{
public class EfStartUpTask : IStartupTask
{
public void Execute()
{
var settings = EngineContext.Current.Resolve<DataSettings>();
if (settings != null && settings.IsValid())
{
var provider = EngineContext.Current.Resolve<IDataProvider>();
if (provider == null)
throw new NopException("No IDataProvider found");
provider.SetDatabaseInitializer();
}
}
public int Order
{
//ensure that this task is run first
get { return -1000; }
}
}
}
EfStartUpTask是初始化EF相关的数据库的操作。
3、IEngine
using System;
using Nop.Core.Configuration;
using Nop.Core.Infrastructure.DependencyManagement;
namespace Nop.Core.Infrastructure
{
/// <summary>
/// Classes implementing this interface can serve as a portal for the
/// various services composing the Nop engine. Edit functionality, modules
/// and implementations access most Nop functionality through this
/// interface.
/// </summary>
public interface IEngine
{
/// <summary>
/// Container manager
/// </summary>
ContainerManager ContainerManager { get; }
/// <summary>
/// Initialize components and plugins in the nop environment.
/// </summary>
/// <param name="config">Config</param>
void Initialize(NopConfig config);
/// <summary>
/// Resolve dependency
/// </summary>
/// <typeparam name="T">T</typeparam>
/// <returns></returns>
T Resolve<T>() where T : class;
/// <summary>
/// Resolve dependency
/// </summary>
/// <param name="type">Type</param>
/// <returns></returns>
object Resolve(Type type);
/// <summary>
/// Resolve dependencies
/// </summary>
/// <typeparam name="T">T</typeparam>
/// <returns></returns>
T[] ResolveAll<T>();
}
}
IEngine是Nop的引擎的抽象接口，抽象提出了一些公共方法，如：设置IoC容器，从IoC容器中获取组件，以及初始化组件、插件到Nop环境。
4、NopEngine
NopEngine类实现了接口IEngine，真正的实现了接口的方法。我们可以在里面看到有两个相关于StartupTask的方法：
// <summary>
/// Run startup tasks
/// </summary>
protected virtual void RunStartupTasks()
{
var typeFinder = _containerManager.Resolve<ITypeFinder>();
var startUpTaskTypes = typeFinder.FindClassesOfType<IStartupTask>();
var startUpTasks = new List<IStartupTask>();
foreach (var startUpTaskType in startUpTaskTypes)
startUpTasks.Add((IStartupTask)Activator.CreateInstance(startUpTaskType));
//sort
startUpTasks = startUpTasks.AsQueryable().OrderBy(st => st.Order).ToList();
foreach (var startUpTask in startUpTasks)
startUpTask.Execute();
}
/// <summary>
/// Initialize components and plugins in the nop environment.
/// </summary>
/// <param name="config">Config</param>
public void Initialize(NopConfig config)
{
//register dependencies
RegisterDependencies(config);
//startup tasks
if (!config.IgnoreStartupTasks)
{
RunStartupTasks();
}
}
可以看到上面通过typeFinder找到所有实现接口IStartupTask的组件，然后通过排序，最后依次调用其Execute()方法。
5、EngineContext
EngineContext提供了访问Nop engine的单例入口。
/// <summary>
/// Creates a factory instance and adds a http application injecting facility.
/// </summary>
/// <param name="config">Config</param>
/// <returns>New engine instance</returns>
protected static IEngine CreateEngineInstance(NopConfig config)
{
if (config != null && !string.IsNullOrEmpty(config.EngineType))
{
var engineType = Type.GetType(config.EngineType);
if (engineType == null)
throw new ConfigurationErrorsException("The type '" + config.EngineType + "' could not be found. Please check the configuration at /configuration/nop/engine[@engineType] or check for missing assemblies.");
if (!typeof(IEngine).IsAssignableFrom(engineType))
throw new ConfigurationErrorsException("The type '" + engineType + "' doesn't implement 'Nop.Core.Infrastructure.IEngine' and cannot be configured in /configuration/nop/engine[@engineType] for that purpose.");
return Activator.CreateInstance(engineType) as IEngine;
}
return new NopEngine();
}
/// <summary>
/// Initializes a static instance of the Nop factory.
/// </summary>
/// <param name="forceRecreate">Creates a new factory instance even though the factory has been previously initialized.</param>
[MethodImpl(MethodImplOptions.Synchronized)]
public static IEngine Initialize(bool forceRecreate)
{
if (Singleton<IEngine>.Instance == null || forceRecreate)
{
var config = ConfigurationManager.GetSection("NopConfig") as NopConfig;
Singleton<IEngine>.Instance = CreateEngineInstance(config);
Singleton<IEngine>.Instance.Initialize(config);
}
return Singleton<IEngine>.Instance;
}
将方法Initialize用 [MethodImpl(MethodImplOptions.Synchronized)] 标识，表示该方法一次只能由一个线程执行，避免多线程创建多个IEngine实例。创建IEngine实例时调用方法CreateEngineInstance，根据Web.config的配置创建相应的IEngine实例。如果在Web.config没有指定Engine的类型，就创建默认的Engine，即NopEngine。由于Nop默认在配置文件中是没有指定Engine的类型的。如下图：
从上图可以看到Engine结点属性Type的值为空，所以EngineContext的CreateEngineInstance会创建一个NopEngine的实例。当然你也可以自己定义一个类并实现接口IEngine，然后在Web.config中在Engine结点中为属性Type填上相应的值。
在创建了相应IEngine的实例之后，最后会调用其Initialize方法（Singleton.Instance.Initialize(config);），也就会执行到任务的startUpTask.Execute()；
6、Global.asax
在程序启动时Global.asax的Application_Start方法会运行，我们可以看到在Application_Start中会有一行代码：
//initialize engine context EngineContext.Initialize(false);
这行代码是启动时执行任务Task的最开始的地方，会一层层地往下执行，直到执行到AutoMapperStartupTask和EfStartUpTask的Execute()方法。
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