利用AOP写2PC框架(二)_.NET_编程开发_程序员俱乐部

AOP的底层已经封装好了以后，我们就要开始针对应用层写具体的业务逻辑了。

也就是说我们需要有个类继承于AopProxyBase，并且重写其After，Bofore以达到我们的拦截记录的功能。代码如下：

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public class TransactionProxy : AopProxyBase
    {
        public TransactionProxy(MarshalByRefObject obj, Type type)
            : base(obj, type)
        { }

        public override void Before(System.Runtime.Remoting.Messaging.IMessage requestMsg, AopMethodAttribute[] attrs)
        {

        }

        public override void After(System.Runtime.Remoting.Messaging.IMessage requestMsg, System.Runtime.Remoting.Messaging.IMessage Respond, AopMethodAttribute[] attrs)
        {
            foreach (var attr in attrs)
            {
                if (attr is LogicRollBackTransAttribute)
                {
                    return;
                }
            }

            var args = requestMsg.Properties["__Args"] as object[];
            string methodName = requestMsg.Properties["__MethodName"] as string;
            CustomTransaction customTrans = null;
            List<object> list = new List<object>();

            customTrans = CallContext.GetData(TransKey.CustomTransKey) as CustomTransaction;
            if (customTrans != null)
            {
                list.AddRange(args);
                TransactionUnit unit = AppTransactionManage.Instance.GetRollBackInfo(methodName);
                if (unit != null)
                {
                    unit.Argments = list;
                }
                customTrans.Compensation.Add(unit);
                CallContext.SetData(TransKey.CustomTransKey, customTrans);
                
                var outArgs = Respond.Properties["__OutArgs"] as object[];
                IDbTransaction dbTrans;
                foreach (var attr in attrs)
                {
                    if (attr is DbTransAttribute || attr is LogicTransAttribute)
                    {
                        if (outArgs != null)
                        {
                            foreach (var arg in outArgs)
                            {
                                if (arg is IDbTransaction)
                                {
                                    dbTrans = arg as IDbTransaction;
                                    if (customTrans != null)
                                    {
                                        customTrans.AddDbTransaction(dbTrans);
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }

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在After的地方，我们可以看到，我们做了一次LogicRollBackTransAttribute的判定，避免在回调的时候，又再走一次拦截和记录的流程。

同时做了DbTransAttribute和LogicTransAttribute的判定。因为我把事务分为两类，一类是db本身自己控制的，可以直接rollback的，一类是logic的，需要我们去手动通过逻辑回滚的。代码如下：

[AttributeUsage(AttributeTargets.Method)]
    public class LogicTransAttribute : AopMethodAttribute
    {
        public string MethodName { get; set; }

        public LogicTransAttribute()
        {

        }

        public LogicTransAttribute(string name)
        {
            this.MethodName = name;
        }
    }

[AttributeUsage(AttributeTargets.Method)]
    public class DbTransAttribute : AopMethodAttribute
    {
        
    }

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同时可以看到，我把每一个函数的调用作为一个单元，用TransactionUnit类来保存，代码如下：

public class TransactionUnit
    {
        public object InstanceObject;
        /// <summary>
        /// 执行的方法
        /// </summary>
        public MethodInfo Forward;
        /// <summary>
        /// 失败回滚的方法
        /// </summary>
        public MethodInfo Rollback;
        /// <summary>
        /// 参数
        /// </summary>
        public IList<object> Argments;
    }

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因为，一个事务里面，可能包含了多次操作redis，或者多次操作db，为了保证线程安全，同时又需要避开锁，我用了CallContext将一个线程里面的一段事务，保存在其线程上下文中。在保存一个完整的TransactionUnit的时候，不可能每一次都去通过反射去取MethodInfo，所以又增加了一段初始化和字典来保存其MethodInfo。代码如下：

public class AppTransactionManage
    {
        private Dictionary<string, TransactionUnit> _transMaps;

        static AppTransactionManage() { }
        private AppTransactionManage()
        {
            if (this._transMaps == null)
            {
                this._transMaps = new Dictionary<string, TransactionUnit>();
            }
        }

        private static AppTransactionManage _instance;
        public static AppTransactionManage Instance
        {
            get
            {
                if (_instance == null)
                {
                    _instance = new AppTransactionManage();
                }
                return _instance;
            }
        }

        public TransactionUnit GetRollBackInfo(string methodName)
        {
            if (this._transMaps == null) throw new ArgumentNullException("not init");
            if (this._transMaps.ContainsKey(methodName))
            {
                return this._transMaps[methodName];
            }
            return null;
        }

        public void Init(params string[] assembly)
        {
            if (assembly != null)
            {
                foreach (string s in assembly)
                {
                    var ass = Assembly.Load(s);
                    if (ass != null)
                    {
                        var types = ass.GetTypes();
                        foreach (var type in types)
                        {
                            var transAttr = type.GetCustomAttribute(typeof(TransactionAttribute), false) as TransactionAttribute;
                            if (transAttr != null)
                            {
                                var methods = type.GetMethods();
                                foreach (var method in methods)
                                {
                                    var forwardTrans = method.GetCustomAttribute(typeof(LogicTransAttribute), false) as LogicTransAttribute;
                                    var rollbackTrans = method.GetCustomAttribute(typeof(LogicRollBackTransAttribute), false) as LogicRollBackTransAttribute;

                                    TransactionUnit unit;
                                    if (forwardTrans != null)
                                    {
                                        if (!this._transMaps.TryGetValue(forwardTrans.MethodName, out unit))
                                        {
                                            unit = new TransactionUnit();
                                        }
                                        unit.Forward = method;
                                        unit.InstanceObject = Activator.CreateInstance(type);
                                        this._transMaps[forwardTrans.MethodName] = unit;
                                    }

                                    if (rollbackTrans != null)
                                    {
                                        if (!this._transMaps.TryGetValue(rollbackTrans.MethodName, out unit))
                                        {
                                            unit = new TransactionUnit();
                                        }
                                        unit.Rollback = method;
                                        unit.InstanceObject = Activator.CreateInstance(type);
                                        this._transMaps[rollbackTrans.MethodName] = unit;
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }

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为了友好开发者的调用，可以让其像使用SqlTransaction一样来使用，我又对外公开了一个CustomTranstion，将调用方式封装在这个类里面，代码如下：

public class CustomTransaction : IDisposable
    {
        private List<IDbTransaction> _dbTransactions;

        private bool _isRollBack = true;

        /// <summary>
        /// 补偿机制
        /// </summary>
        public List<TransactionUnit> Compensation;
        
        public void Commit()
        {
            if (this._dbTransactions != null)
            {
                this._dbTransactions.ForEach((t) => t.Commit());
            }
            this._isRollBack = false;
        }

        public void RollBack()
        {
            if (this.Compensation != null)
            {
                this.Compensation.ForEach((t) => 
                {
                    object[] paramsArray = t.Argments == null ? null : t.Argments.ToArray();
                    t.Rollback.Invoke(t.InstanceObject, paramsArray);
                });
            }
            if (this._dbTransactions != null)
            {
                this._dbTransactions.ForEach((t) => t.Rollback());
            }
        }

        private bool _isRetry = true;

        public CustomTransaction(bool isRetry = true)
        {
            this._isRetry = isRetry;
            if (this._dbTransactions == null)
            {
                this._dbTransactions = new List<IDbTransaction>();
            }
            if (this.Compensation == null)
            {
                this.Compensation = new List<TransactionUnit>();
            }
            CallContext.SetData(TransKey.CustomTransKey, this);
        }


        public void AddDbTransaction(IDbTransaction transaction)
        {
            this._dbTransactions.Add(transaction);
        }

        public void Dispose()
        {
            if (this._isRollBack)
            {
                this.RollBack();
            }
            CallContext.FreeNamedDataSlot(TransKey.CustomTransKey);
        }
    }

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 这个时候，你就可以像是用SqlTransaction一样去Using(var trans = new CustomTranstion()){}然后在using里面去写trans.Commit();来提交所有的事务操作，如果不做Commit操作的话，在CustomTranstion里面，会自动去调用其rollback()操作。

但是这并没有完，所有的只是记录下来了，但是并没有保存到DB去做持久化。这个时候就需要增加一个队列，来不断的去将TransactionUnit来保存到db，同时又需要把队列去做持久化，避免一些意外原因，导致队列数据丢失，而缺失了这部分的日志记录(虽然我个人认为这一部分可以省略)。代码如下：

[Serializable]
    public class TransQueue : IDisposable
    {
        public Queue<Action> _transQueue;
        private Thread _thread;
        private bool _isDispose;

        public delegate void PersistenceHandler(Action[] actions);

        PersistenceHandler persistenceHandler;
        private readonly object _syncObject = new object();
        public TransQueue()
        {
            if (_transQueue == null)
            {
                _transQueue = new Queue<Action>();
            }
            if (persistenceHandler == null)
            {
                persistenceHandler = PersistenceToDisk;
            }

            if (_thread == null)
            {
                _thread = new Thread(Thread_Work)
                {
                    IsBackground = true
                };
            }
            _thread.Start();
        }

        public void Push(Action action)
        {
            if (_transQueue == null) throw new ArgumentNullException("transQueue is not init");

            lock (_syncObject)
            {
                _transQueue.Enqueue(action);
            }
        }

        public void Thread_Work()
        {
            while (!_isDispose)
            {
                Action[] items = null;
                if (_transQueue != null && _transQueue.Count > 0)
                {
                    lock (_syncObject)
                    {
                        items = new Action[_transQueue.Count];
                        _transQueue.CopyTo(items, 0);
                    }
                }

                if (items != null && items.Length > 0)
                {
                    persistenceHandler.BeginInvoke(items, PersistenceHandlerCallBack, persistenceHandler);
                    foreach (var item in items)
                    {
                        item.Invoke();
                    }
                }
            }
        }

        public void PersistenceHandlerCallBack(IAsyncResult result)
        {
            try
            {
                (result.AsyncState as PersistenceHandler).EndInvoke(result);
            }
            catch (Exception e)
            {
            }
        }

        public void PersistenceToDisk(Action[] items)
        {
            BinaryHelper.SaveToFile(items);
        }

        public void Dispose()
        {
            _isDispose = true;
            _thread.Join();
        }

    }




 public class TransQueueManage
    {
        private int _threadNumber = 2;
        private TransQueue[] _transQueue;
        Random random = new Random();
        private TransQueueManage()
        {
            if(_transQueue == null)
            {
                _transQueue = new TransQueue[_threadNumber];
                for (var i = 0; i < _threadNumber; i++)
                {
                    _transQueue[i] = new TransQueue();
                }
            }
        }

        static TransQueueManage()
        {
            
        }


        private static readonly object _syncObject = new object();
        private static TransQueueManage _instance;
        public static TransQueueManage Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (_syncObject)
                    {
                        if (_instance == null)
                        {
                            _instance = new TransQueueManage();
                        }
                    }
                }
                return _instance;
            }
        }

        public void Push(Action action)
        {
            var index = GetRandomThreadIndex();
            _transQueue[index].Push(action);
        }

        public int GetRandomThreadIndex()
        {
            return random.Next(0, _threadNumber);
        }
    }

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