AbpVnext 本地事件匯流排

補充知識

發佈訂閱

概念

應用場景

本地事件匯流排允許服務發佈和訂閱進程內事件，這意味著如果兩個服務>(發佈者和訂閱者)在同一個進程中運行，那麼它是合適的

完整示例
DDD開發規範: 先定義好介面層、後實現層、暴露介面

對於要更新的實體

//領域層的實體
public class Book : FullAuditedEntity<Guid>, IHasExtraProperties, IMultiTenant
{
   public string Name{get;set;}

   public string Author {get;set;}

   public long Price {get;set}
   
   public string Title {get;set;}

   public string Classify{get;set;}

   //條形碼
   public string BarCode {get;set;}
   // 出版商
   public string Issue{get;set;}
   // 頁數
   public string PageTotal{get;set;}
  
   public string BuyerId{get;set;}

   public DateTime? ModifyTime{get;set}
}

//這個實體是必須有的
public class BookRecordEto{

    public string Name{get;set;}

    public string Author {get;set;}

    public long Price {get;set}

    public DateTime? ModifyTime{get;set}
}

//發佈事件
public class BookService: ITransientDependency
{
    //Abp使用了字典來保存對實例的引用
    public IAbpLazyServiceProvider LazyServiceProvider { get; set; }

    //按需註入
    protected ILocalEventBus  LocalEventBus => LazyServiceProvider.LazyGetRequiredService<ILocalEventBus >(); 

    //倉儲--對應Book的資料庫表
    protected IBookRepository BookRepository => LazyGetRequiredService<IBookRepository>();

    public async Task UpdateData(Guid id)
    {
        var book =  await BookRepository.FindAsync(x=>x.Id = id);
        if (book == null){//不存在實體}
        var updateEntity = await BookRepository.UpdateAsync(book);
        if (updateEntity == null){//更新失敗}
        
        //實體數據發生變更，發佈事件
        await LocalEventBus.PublishAsync(new BookEto(){
            Name = book.Name;
            Author = book.Author;
            Price = book.Price;
            ModifyTime = DateTime.Now;
        });
    } 
}

//訂閱事件
using Volo.Abp.DependencyInjection;
using Volo.Abp.EventBus;
public class EventBusHandler: ApplicationService,
      , ILocalEventHandler<BookRecordEto> 
      , ITransientDependency
{
    // 進行業務數據更新，比如要更新購買這邊書讀者記錄
    public IAbpLazyServiceProvider LazyServiceProvider{get;set;}
 
    protected IBookBoughtRecordRepository BoughtRecordRepository => LazyServiceProvider.LazyGetRequiredService<IBookBoughtRecordRepository>();

    [UnitOfWork]//這個特性以及方法頭裡面的virtual很重要
    public async virtual Task HandleEventAsync(BookRecordEto eventData)
    {
        //獲取購買記錄
        var record =  await  BoughtRecordRepository.GetQueryableAsync();

        var recordList = await AsyncExecuter.ToListAsync(record);
        
        if(recordList.Count() != 0){

            var boughtRecord  = ObjectMapper.Map(eventData, new BoughtRecord());
            //插入一條數據
            await BoughtRecordRepository.InsertAsync(boughtRecord);
        }
    }
}

總結