幸福框架：在应用层实现触发器-白红宇

幸福框架：在应用层实现触发器

阅读量：6049 次

发布时间：2019-06-20

本文共 5413 字，大约阅读时间需要 18 分钟。

背景

企业应用开发过程中经常面对一些非功能型需求，如：自动收集和设置审计信息、索引和关系约束，有些非功能需求当然可以用数据库自带的功能，如索引约束，但是应用层视乎也有必要重复一次，因为当违背这种约束的时候我们希望提示给用户友好的信息，如：‘xxx已经存在，xxx必须唯一’，这篇文章我就介绍一个简单的方案应对这种需求。

思路

我觉得数据库的触发器是个好东西，应用层完全可以借用一下，我还认为如果我在应用层实现了触发器，像一些前置条件和后置条件验证也可以用触发器实现（这块我不是很清楚设计的是否合理，还是要引入另外一个继承体系）。

实现

核心类

核心代码

DefaultTriggerService.cs

1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Threading.Tasks; 6  7 using Microsoft.Practices.ServiceLocation; 8  9 using Happy.Domain;10 11 namespace Happy.Application.Trigger.Internal12 {13     internal sealed class DefaultTriggerService : ITriggerService14     {15         public void ExecuteBeforeInsert
     
      (TAggregateRoot aggregate)16             where TAggregateRoot : AggregateRoot17         {18             var triggers = ServiceLocator19                 .Current20                 .GetAllInstances
      
       
        >();21 22             foreach (var trigger in triggers)23             {24                 trigger.BeforeInsert(aggregate);25             }26         }27 28         public void ExecuteAfterInsert
        
         (TAggregateRoot aggregate)29             where TAggregateRoot : AggregateRoot30         {31             var triggers = ServiceLocator32                 .Current33                 .GetAllInstances
         
          
           >();34 35 foreach (var trigger in triggers)36 {37 trigger.AfterInsert(aggregate);38 }39 }40 41 public void ExecuteBeforeUpdate
           
            (TAggregateRoot aggregate)42 where TAggregateRoot : AggregateRoot43 {44 var triggers = ServiceLocator45 .Current46 .GetAllInstances
            
             
              >();47 48 foreach (var trigger in triggers)49 {50 trigger.BeforeUpdate(aggregate);51 }52 }53 54 public void ExecuteAfterUpdate
              
               (TAggregateRoot aggregate)55 where TAggregateRoot : AggregateRoot56 {57 var triggers = ServiceLocator58 .Current59 .GetAllInstances
               
                
                 >();60 61 foreach (var trigger in triggers)62 {63 trigger.AfterUpdate(aggregate);64 }65 }66 67 public void ExecuteBeforeDelete
                 
                  (TAggregateRoot aggregate)68 where TAggregateRoot : AggregateRoot69 {70 var triggers = ServiceLocator71 .Current72 .GetAllInstances
                  
                   
                    >();73 74 foreach (var trigger in triggers)75 {76 trigger.BeforeDelete(aggregate);77 }78 }79 80 public void ExecuteAfterDelete
                    
                     (TAggregateRoot aggregate)81 where TAggregateRoot : AggregateRoot82 {83 var triggers = ServiceLocator84 .Current85 .GetAllInstances
                     
                      
                       >();86 87 foreach (var trigger in triggers)88 {89 trigger.AfterDelete(aggregate);90 }91 }92 }93 }

自动管理树形节点的路径信息

代码

ITreeNode.cs

1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Threading.Tasks; 6  7 namespace Happy.Domain.Feature 8 { 9     /// 10     /// 树的节点。11     /// 
12     public interface ITreeNode13     {14         /// 15         /// 节点ID。16         /// 
17         Guid Id { get; set; }18 19         /// 20         /// 父节点ID。21         /// 
22         Guid ParentId { get; set; }23 24         /// 25         /// 节点在树中的路径，如：/A/B/C/D，包含自己。26         /// 
27         string NodePath { get; set; }28     }29 }

TreeNodeTrigger.cs

1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 using System.Threading.Tasks; 6  7 using Happy.ExtensionMethod; 8 using Happy.Domain; 9 using Happy.Domain.Feature;10 using Happy.Application.Trigger;11 12 namespace Happy.EntityFramework.Trigger13 {14     public class TreeNodeTrigger
     
       : TriggerBase
      
       15         where TUnitOfWork : UnitOfWork16         where TAgggregateRoot : AggregateRoot, ITreeNode17     {18         public override void BeforeInsert(TAgggregateRoot aggregate)19         {20             var parentNodePath = this.GetParentNodePath(aggregate);21 22             aggregate.NodePath = parentNodePath + "/" + aggregate.Id;23         }24 25         public override void BeforeUpdate(TAgggregateRoot aggregate)26         {27             var newParentNodePath = this.GetParentNodePath(aggregate);28             var newNodePath = newParentNodePath + "/" + aggregate.Id;29             var oldNodePath = aggregate.NodePath;30 31             if (oldNodePath == newNodePath)32             {33                 return;34             }35 36             aggregate.NodePath = newNodePath;37 38             var table = typeof(TAgggregateRoot).Name.ToPluralize();39             var sql = string.Format("UPDATE {0} SET NodePath = REPLACE(NodePath, {
    {0}}, {
    {1}}) WHERE NodePath LIKE {
    {2}}", table);40             this.UnitOfWork.Database.ExecuteSqlCommand(sql, oldNodePath, newNodePath, oldNodePath + "/%");41         }42 43         public override void BeforeDelete(TAgggregateRoot aggregate)44         {45             var table = typeof(TAgggregateRoot).Name.ToPluralize();46             var sql = string.Format("DELETE FROM {0} WHERE NodePath LIKE {
    {0}}", table);47             this.UnitOfWork.Database.ExecuteSqlCommand(sql, aggregate.NodePath + "/%");48         }49 50         private string GetParentNodePath(TAgggregateRoot aggregate)51         {52             var table = typeof(TAgggregateRoot).Name.ToPluralize();53             var sql = string.Format("SELECT NodePath FROM {0} WHERE Id = {
    {0}}", table);54             return this.UnitOfWork.Database.SqlQuery
       
        (sql, aggregate.ParentId).FirstOrDefault();55         }56     }57 }

运行效果

备注

这种触发器我在项目中有用过，虽然有所不足，如批量操作性能不高，但是在很多场景下，也减少了不少的重复代码。

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