初始化入口
在AbpKernelModule类中,通过UnitOfWorkRegistrar.Initialize(IocManager) 方法去初始化
1 /// <summary> 2 /// This class is used to register interceptor for needed classes for Unit Of Work mechanism. 3 /// </summary> 4 internal static class UnitOfWorkRegistrar 5 { 6 /// <summary> 7 /// Initializes the registerer. 8 /// </summary> 9 /// <param name="iocManager">IOC manager</param> 10 public static void Initialize(IIocManager iocManager) 11 { 12 iocManager.IocContainer.Kernel.ComponentRegistered += ComponentRegistered; 13 } 14 15 private static void ComponentRegistered(string key, IHandler handler) 16 { 17 if (UnitOfWorkHelper.IsConventionalUowClass(handler.ComponentModel.Implementation)) 18 { 19 //Intercept all methods of all repositories. 20 handler.ComponentModel.Interceptors.Add(new InterceptorReference(typeof(UnitOfWorkInterceptor))); 21 } 22 else if (handler.ComponentModel.Implementation.GetMethods(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).Any(UnitOfWorkHelper.HasUnitOfWorkAttribute)) 23 { 24 //Intercept all methods of classes those have at least one method that has UnitOfWork attribute. 25 //TODO: Intecept only UnitOfWork methods, not other methods! 26 handler.ComponentModel.Interceptors.Add(new InterceptorReference(typeof(UnitOfWorkInterceptor))); 27 } 28 } 29 }
UnitOfWorkInterceptor 拦截器
基于Castle.Core的AOP动态拦截
区分同步异步,通过UowManager开启事务
1 private void PerformUow(IInvocation invocation, UnitOfWorkOptions options) 2 { 3 if (AsyncHelper.IsAsyncMethod(invocation.Method)) 4 { 5 PerformAsyncUow(invocation, options); 6 } 7 else 8 { 9 PerformSyncUow(invocation, options); 10 } 11 } 12 13 private void PerformSyncUow(IInvocation invocation, UnitOfWorkOptions options) 14 { 15 using (var uow = _unitOfWorkManager.Begin(options)) 16 { 17 invocation.Proceed(); 18 uow.Complete(); 19 } 20 }
invocation.Proceed();会嵌套执行,将Uow嵌套包含,嵌套的Uow不会单独再开启事务,通过InnerUnitOfWorkCompleteHandle标识,全部完成后complete,提交事务(UnitOfWorkDefaultOptions默认开启事务)
UnitOfWorkManager
UnitOfWorkManager 继承IUnitOfWorkManager
1 /// <summary> 2 /// Unit of work manager. 3 /// Used to begin and control a unit of work. 4 /// </summary> 5 public interface IUnitOfWorkManager 6 { 7 /// <summary> 8 /// Gets currently active unit of work (or null if not exists). 9 /// </summary> 10 IActiveUnitOfWork Current { get; } 11 12 /// <summary> 13 /// Begins a new unit of work. 14 /// </summary> 15 /// <returns>A handle to be able to complete the unit of work</returns> 16 IUnitOfWorkCompleteHandle Begin(); 17 18 /// <summary> 19 /// Begins a new unit of work. 20 /// </summary> 21 /// <returns>A handle to be able to complete the unit of work</returns> 22 IUnitOfWorkCompleteHandle Begin(TransactionScopeOption scope); 23 24 /// <summary> 25 /// Begins a new unit of work. 26 /// </summary> 27 /// <returns>A handle to be able to complete the unit of work</returns> 28 IUnitOfWorkCompleteHandle Begin(UnitOfWorkOptions options); 29 }
在Begin方法中根据option的设置,创建了一个新的Uow,并设置了Uow相应的Completed,Failed,Disposed的方法。
CallContextCurrentUnitOfWorkProvider
这里有必要提一下CallContextCurrentUnitOfWorkProvider 的对象,他继承ICurrentUnitOfWorkProvider
CallContextCurrentUnitOfWorkProvider的主要功能其实只有一个:通过current返回当前UOW环境下的UOW实例。
一般思路是:将IUnitOfWork对象定义为实例变量或者是类变量。 但是两者事实上都不可行。
如果定义为类变量,那就会面临线程安全的问题,解决方式无非加锁,但会导致并发能力下降,ABP是web框架,因为锁导致并发能力下降是不能接受的。
如果定义为实例变量,在同一线程其他地方resolve CallContextCurrentUnitOfWorkProvider这个实例的时候都会得到一个新的实例,新的实例下current自然是NULL.
ABP的做法是:线程逻辑上下文+线程安全的Dictinoray容器。
线程逻辑上下文用于存储UOW实例的key, 而线程逻辑上下文对于本线程是全局可访问的,而同时具有天然的隔离性。这就确保了当前线程的各个地方都可以得到current的UOW的key
线程安全的Dictinoray容器是一个类实例,用于存放UOW的实例,通过UOW的key就可以取到UOW的实例。(引用: http://www.cnblogs.com/1zhk/p/5309043.html)
这里有两篇CallContext的博文,推荐看一下
如何实现对上下文(Context)数据的统一管理 [提供源代码下载]
CallContext和多线程
UnitOfWork
1.UnitOfWorkBase
接下来,分析下UnitOfWork是如何封装事务的。
基于接口隔离原则的考量,ABP作者将UnitOfWork的方法分到了三个不同的接口中,如下图。
IUnitOfWorkCompleteHandle:定义了UOW同步和异步的complete方法。实现UOW完成时候的逻辑。
IActiveUnitOfWork:一个UOW除了以上两个接口中定义的方法和属性外,其他的属性和方法都在这个接口定义的。比如Completed,Disposed,Failed事件代理,Filter的enable和disable,以及同步、异步的SaveChanges方法。
IUnitOfWork:继承了上面两个接口。定义了外层的IUnitOfWork的引用和UOW的begin方法。 ABP是通过构建一个UnitOfWork的链,将不同的方法纳入到一个事务中。
UnitOfWorkBase:这个抽象类实现了上面三个接口中定义的方法,而真正实现事务控制的方法是由这个抽象类的子类实现的(比如,真正创建TransactionScope的操作是在EfUnitOfWork,NhUnitOfWork这样的之类中实现的)。UOW中除了事务控制逻辑以外的逻辑都是由UnitOfWorkBase抽象类实现的。
1 /// <summary> 2 /// Defines a unit of work. 3 /// This interface is internally used by ABP. 4 /// Use <see cref="IUnitOfWorkManager.Begin()"/> to start a new unit of work. 5 /// </summary> 6 public interface IUnitOfWork : IActiveUnitOfWork, IUnitOfWorkCompleteHandle 7 { 8 /// <summary> 9 /// Unique id of this UOW. 10 /// </summary> 11 string Id { get; } 12 13 /// <summary> 14 /// Reference to the outer UOW if exists. 15 /// </summary> 16 IUnitOfWork Outer { get; set; } 17 18 /// <summary> 19 /// Begins the unit of work with given options. 20 /// </summary> 21 /// <param name="options">Unit of work options</param> 22 void Begin(UnitOfWorkOptions options); 23 }
UnitOfWorkBase中的Begin实现如下:
1 public void Begin(UnitOfWorkOptions options) 2 { 3 if (options == null) 4 { 5 throw new ArgumentNullException("options"); 6 } 7 8 PreventMultipleBegin(); //通过_isBeginCalledBefore 字段bool判断是否已经begin 9 Options = options; //TODO: Do not set options like that, instead make a copy? 10 11 SetFilters(options.FilterOverrides); //通过设置过滤器达到全局数据过滤的效果,在ef的实现中,通过引用EntityFramework.DynamicFilter实现 12 13 BeginUow(); 14 }
2.开始UnitOfWork
CompleteUow和BeginUow 在UowBase中为抽象方法,具体实现在efUow中,稍后分析
/// <summary>/// Should be implemented by derived classes to complete UOW./// </summary>protected abstract void CompleteUow();
3.Complete
Complete方法在UnitOfWorkInterceptor拦截中,PerformSyncUow方法内,执行完invocation.Proceed();会调用Complete方法。
1 /// <inheritdoc/> 2 public void Complete() 3 { 4 PreventMultipleComplete(); //通过_isCompleteCalledBefore字段Bool判断是否已经Complete,保证只执行一次 5 try 6 { 7 CompleteUow(); 8 _succeed = true; 9 OnCompleted(); //调用完成的事件,在UnitOfWorkManager中设置,当前的UnitOfWork为null 10 } 11 catch (Exception ex) 12 { 13 _exception = ex; 14 throw; 15 } 16 }
4.Dispose
1 /// <inheritdoc/> 2 public void Dispose() 3 { 4 if (IsDisposed) 5 { 6 return; 7 } 8 9 IsDisposed = true; 10 11 if (!_succeed) //在Complete是会设置_succeed,没有成功则执行Faild事件,会将当前的UnitOfWord设为null 12 { 13 OnFailed(_exception); 14 } 15 16 DisposeUow(); //为抽象方法,在子类中实现 17 OnDisposed(); //OnFailed和OnDisposed均在UnitOfWordManage中设置 18 }
EfUnitOfWork
1.BeginUow
1 protected override void BeginUow() 2 { 3 if (Options.IsTransactional == true) 4 { 5 var transactionOptions = new TransactionOptions 6 { 7 IsolationLevel = Options.IsolationLevel.GetValueOrDefault(IsolationLevel.ReadUncommitted), 8 }; 9 10 if (Options.Timeout.HasValue) 11 { 12 transactionOptions.Timeout = Options.Timeout.Value; 13 } 14 15 CurrentTransaction = new TransactionScope( //开启事务,并给定默认为Required 16 Options.Scope.GetValueOrDefault(TransactionScopeOption.Required), 17 transactionOptions, 18 Options.AsyncFlowOption.GetValueOrDefault(TransactionScopeAsyncFlowOption.Enabled) 19 ); 20 } 21 }
2.CompleteUow
1 protected override void CompleteUow() 2 { 3 SaveChanges(); //遍历EfContent,调用SaveChange方法 4 if (CurrentTransaction != null) //如果存在事务则执行 5 { 6 CurrentTransaction.Complete(); 7 } 8 }