mirror of https://github.com/abpframework/abp.git
albert
4 years ago
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26 changed files with 623 additions and 145 deletions
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# Background Jobs Module |
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# 后台作业模块 |
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待添加 |
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后台作业模块实现了 `IBackgroundJobStore` 接口,并且可以使用ABP框架的默认后台作业管理.如果你不想使用这个模块,那么你需要自己实现 `IBackgroundJobStore` 接口. |
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> 本文档仅介绍后台作业模块,该模块将后台作业持久化到数据库.有关后台作业系统的更多信息,请参阅[后台作业](../Background-Jobs.md)文档. |
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## 如何使用 |
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当你使用ABP框架[创建一个新的解决方案](https://abp.io/get-started)时,这个模块是（作为NuGet/NPM包）预先安装的.你可以继续将其作为软件包使用并轻松获取更新,也可以将其源代码包含到解决方案中（请参阅 `get-source` [CLI](../CLI.md)命令）以开发自定义模块. |
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### 源代码 |
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此模块的源代码可在[此处](https://github.com/abpframework/abp/tree/dev/modules/background-jobs)访问.源代码是由[MIT](https://choosealicense.com/licenses/mit/)授权的,所以你可以自由使用和定制它. |
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## 内部结构 |
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### 领域层 |
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#### 聚合 |
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- `BackgroundJobRecord` (聚合根): 表示后台工作记录. |
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#### 仓储 |
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为该模块定义了以下自定义仓储: |
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- `IBackgroundJobRepository` |
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### 数据库提供程序 |
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#### 通用 |
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##### 表/集合的前缀与架构 |
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默认情况下,所有表/集合都使用 `Abp` 前缀.如果需要更改表前缀或设置架构名称（如果数据库提供程序支持）,请在 `BackgroundJobsDbProperties` 类上设置静态属性. |
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##### 连接字符串 |
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此模块使用 `AbpBackgroundJobs` 作为连接字符串名称.如果不使用此名称定义连接字符串,它将返回 `Default` 连接字符串.有关详细信息,请参阅[连接字符串](https://docs.abp.io/en/abp/latest/Connection-Strings)文档. |
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#### Entity Framework Core |
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##### 表 |
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- **AbpBackgroundJobs** |
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#### MongoDB |
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##### 集合 |
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- **AbpBackgroundJobs** |
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## 另请参阅 |
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* [后台作业系统](../Background-Jobs.md) |
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## 规约 |
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TODO.. |
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规约模式用于为实体和其他业务对象定义 **命名、可复用、可组合和可测试的过滤器** . |
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> 规约是领域层的一部分. |
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## 安装 |
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> 这个包 **已经安装** 在启动模板中.所以,大多数时候你不需要手动去安装. |
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添加 [Volo.Abp.Specifications](https://abp.io/package-detail/Volo.Abp.Specifications) 包到你的项目. 如果当前文件夹是你的项目的根目录(`.csproj`)时,你可以在命令行终端中使用 [ABP CLI](CLI.md) *add package* 命令: |
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````bash |
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abp add-package Volo.Abp.Specifications |
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```` |
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## 定义规约 |
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假设你定义了如下的顾客实体: |
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````csharp |
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using System; |
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using Volo.Abp.Domain.Entities; |
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namespace MyProject |
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{ |
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public class Customer : AggregateRoot<Guid> |
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{ |
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public string Name { get; set; } |
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public byte Age { get; set; } |
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public long Balance { get; set; } |
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public string Location { get; set; } |
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} |
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} |
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```` |
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你可以创建一个由 `Specification<Customer>` 派生的新规约类. |
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**例如:规定选择一个18岁以上的顾客** |
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````csharp |
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using System; |
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using System.Linq.Expressions; |
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using Volo.Abp.Specifications; |
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namespace MyProject |
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{ |
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public class Age18PlusCustomerSpecification : Specification<Customer> |
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{ |
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public override Expression<Func<Customer, bool>> ToExpression() |
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{ |
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return c => c.Age >= 18; |
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} |
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} |
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} |
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```` |
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你只需通过定义一个lambda[表达式](https://docs.microsoft.com/zh-cn/dotnet/csharp/language-reference/operators/lambda-expressions)来定义规约. |
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> 你也可以直接实现`ISpecification<T>`接口,但是基类`Specification<T>`做了大量简化. |
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## 使用规约 |
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这里有两种常见的规约用例. |
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### IsSatisfiedBy |
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`IsSatisfiedBy` 方法可以用于检查单个对象是否满足规约. |
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**例如:如果顾客不满足年龄规定,则抛出异常** |
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````csharp |
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using System; |
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using System.Threading.Tasks; |
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using Volo.Abp.DependencyInjection; |
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namespace MyProject |
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{ |
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public class CustomerService : ITransientDependency |
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{ |
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public async Task BuyAlcohol(Customer customer) |
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{ |
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if (!new Age18PlusCustomerSpecification().IsSatisfiedBy(customer)) |
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{ |
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throw new Exception( |
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"这位顾客不满足年龄规定!" |
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); |
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} |
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//TODO... |
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} |
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} |
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} |
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```` |
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### ToExpression & Repositories |
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`ToExpression()` 方法可用于将规约转化为表达式.通过这种方式,你可以使用规约在**数据库查询时过滤实体**. |
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````csharp |
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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using System.Threading.Tasks; |
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using Volo.Abp.DependencyInjection; |
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using Volo.Abp.Domain.Repositories; |
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using Volo.Abp.Domain.Services; |
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namespace MyProject |
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{ |
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public class CustomerManager : DomainService, ITransientDependency |
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{ |
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private readonly IRepository<Customer, Guid> _customerRepository; |
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public CustomerManager(IRepository<Customer, Guid> customerRepository) |
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{ |
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_customerRepository = customerRepository; |
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} |
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public async Task<List<Customer>> GetCustomersCanBuyAlcohol() |
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{ |
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var queryable = await _customerRepository.GetQueryableAsync(); |
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var query = queryable.Where( |
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new Age18PlusCustomerSpecification().ToExpression() |
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); |
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return await AsyncExecuter.ToListAsync(query); |
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} |
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} |
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} |
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```` |
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> 规约被正确地转换为SQL/数据库查询语句,并且在DBMS端高效执行.虽然它与规约无关,但如果你想了解有关 `AsyncExecuter` 的更多信息,请参阅[仓储](Repositories.md)文档. |
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实际上,没有必要使用 `ToExpression()` 方法,因为规约会自动转换为表达式.这也会起作用: |
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````csharp |
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var queryable = await _customerRepository.GetQueryableAsync(); |
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var query = queryable.Where( |
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new Age18PlusCustomerSpecification() |
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); |
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```` |
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## 编写规约 |
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规约有一个强大的功能是,它们可以与`And`、`Or`、`Not`以及`AndNot`扩展方法组合使用. |
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假设你有另一个规约,定义如下: |
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```csharp |
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using System; |
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using System.Linq.Expressions; |
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using Volo.Abp.Specifications; |
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namespace MyProject |
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{ |
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public class PremiumCustomerSpecification : Specification<Customer> |
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{ |
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public override Expression<Func<Customer, bool>> ToExpression() |
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{ |
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return (customer) => (customer.Balance >= 100000); |
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} |
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} |
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} |
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``` |
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你可以将 `PremiumCustomerSpecification` 和 `Age18PlusCustomerSpecification` 结合起来,查询优质成人顾客的数量,如下所示: |
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````csharp |
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using System; |
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using System.Threading.Tasks; |
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using Volo.Abp.DependencyInjection; |
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using Volo.Abp.Domain.Repositories; |
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using Volo.Abp.Domain.Services; |
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using Volo.Abp.Specifications; |
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namespace MyProject |
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{ |
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public class CustomerManager : DomainService, ITransientDependency |
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{ |
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private readonly IRepository<Customer, Guid> _customerRepository; |
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public CustomerManager(IRepository<Customer, Guid> customerRepository) |
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{ |
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_customerRepository = customerRepository; |
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} |
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public async Task<int> GetAdultPremiumCustomerCountAsync() |
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{ |
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return await _customerRepository.CountAsync( |
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new Age18PlusCustomerSpecification() |
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.And(new PremiumCustomerSpecification()).ToExpression() |
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); |
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} |
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} |
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} |
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```` |
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如果你想让这个组合成为一个可复用的规约,你可以创建这样一个组合的规约类,它派生自`AndSpecification`: |
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````csharp |
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using Volo.Abp.Specifications; |
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namespace MyProject |
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{ |
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public class AdultPremiumCustomerSpecification : AndSpecification<Customer> |
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{ |
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public AdultPremiumCustomerSpecification() |
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: base(new Age18PlusCustomerSpecification(), |
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new PremiumCustomerSpecification()) |
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{ |
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} |
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} |
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} |
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```` |
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现在,你就可以向下面一样重新编写 `GetAdultPremiumCustomerCountAsync` 方法: |
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````csharp |
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public async Task<int> GetAdultPremiumCustomerCountAsync() |
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{ |
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return await _customerRepository.CountAsync( |
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new AdultPremiumCustomerSpecification() |
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); |
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} |
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```` |
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> 你可以从这些例子中看到规约的强大之处.如果你之后想要更改 `PremiumCustomerSpecification` ,比如将余额从 `100.000` 修改为 `200.000` ,所有查询语句和合并的规约都将受到本次更改的影响.这是减少代码重复的好方法！ |
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## 讨论 |
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虽然规约模式通常与C#的lambda表达式相比较,算是一种更老的方式.一些开发人员可能认为不再需要它,我们可以直接将表达式传入到仓储或领域服务中,如下所示: |
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````csharp |
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var count = await _customerRepository.CountAsync(c => c.Balance > 100000 && c.Age => 18); |
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```` |
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自从ABP的[仓储](Repositories.md)支持表达式,这是一个完全有效的用法.你不必在应用程序中定义或使用任何规约,可以直接使用表达式. |
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所以,规约的意义是什么?为什么或者应该在什么时候考虑去使用它? |
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### 何时使用? |
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使用规约的一些好处: |
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- **可复用**:假设你在代码库的许多地方都需要用到优质顾客过滤器.如果使用表达式而不创建规约,那么如果以后更改“优质顾客”的定义会发生什么?假设你想将最低余额从100000美元更改为250000美元,并添加另一个条件,成为顾客超过3年.如果使用了规约,只需修改一个类.如果在任何其他地方重复（复制/粘贴）相同的表达式,则需要更改所有的表达式. |
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- **可组合**:可以组合多个规约来创建新规约.这是另一种可复用性. |
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- **命名**:`PremiumCustomerSpecification` 更好地解释了为什么使用规约,而不是复杂的表达式.因此,如果在你的业务中使用了一个有意义的表达式,请考虑使用规约. |
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- **可测试**:规约是一个单独（且易于）测试的对象. |
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### 什么时侯不要使用? |
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- **没有业务含义的表达式**:不要对与业务无关的表达式和操作使用规约. |
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- **报表**:如果只是创建报表,不要创建规约,而是直接使用 `IQueryable` 和LINQ表达式.你甚至可以使用普通SQL、视图或其他工具生成报表.DDD不关心报表,因此从性能角度来看,查询底层数据存储的方式可能很重要. |
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@ -1,5 +1,8 @@ |
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module.exports = { |
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mappings: { |
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"@node_modules/codemirror/lib/*.*": "@libs/codemirror/" |
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"@node_modules/codemirror/lib/*.*": "@libs/codemirror/", |
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"@node_modules/codemirror/mode/**/*.*": "@libs/codemirror/mode/", |
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"@node_modules/codemirror/theme/**/*.*": "@libs/codemirror/theme/", |
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"@node_modules/codemirror/addon/**/*.*": "@libs/codemirror/addon/" |
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} |
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} |
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@ -0,0 +1,13 @@ |
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@using System.Net.Http |
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@using Microsoft.AspNetCore.Authorization |
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@using Microsoft.AspNetCore.Components.Authorization |
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@using Microsoft.AspNetCore.Components.Forms |
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@using Microsoft.AspNetCore.Components.Routing |
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@using Microsoft.AspNetCore.Components.Web |
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@using Microsoft.AspNetCore.Components.Web.Virtualization |
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@using Microsoft.JSInterop |
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@using MyCompanyName.MyProjectName.Blazor.Server |
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@using Blazorise |
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@using Blazorise.DataGrid |
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@using Volo.Abp.BlazoriseUI |
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@using Volo.Abp.BlazoriseUI.Components |
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