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298 lines
8.3 KiB
298 lines
8.3 KiB
## 应用服务
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应用服务实现应用程序的**用例**, 将**领域层逻辑公开给表示层**.
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从表示层(可选)调用应用服务,**DTO (数据传对象)** 作为参数. 返回(可选)DTO给表示层.
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## 示例
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### 图书实体
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假设你有一个`Book`实体(聚合根), 如下所示:
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````csharp
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public class Book : AggregateRoot<Guid>
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{
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public const int MaxNameLength = 128;
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public virtual string Name { get; protected set; }
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public virtual BookType Type { get; set; }
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public virtual float? Price { get; set; }
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protected Book()
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{
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}
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public Book(Guid id, [NotNull] string name, BookType type, float? price = 0)
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{
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Id = id;
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Name = CheckName(name);
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Type = type;
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Price = price;
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}
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public virtual void ChangeName([NotNull] string name)
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{
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Name = CheckName(name);
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}
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private static string CheckName(string name)
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{
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if (string.IsNullOrWhiteSpace(name))
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{
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throw new ArgumentException($"name can not be empty or white space!");
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}
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if (name.Length > MaxNameLength)
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{
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throw new ArgumentException($"name can not be longer than {MaxNameLength} chars!");
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}
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return name;
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}
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}
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````
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* `Book`实体中定义`MaxNameLength`限制`Name`属性的最大长度.
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* `Book`构造函数与`ChangeName`确保`Name`属性值的有效性. 请注意, `Name`的setter不是`public`.
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ABP不会强制开发者这样设计实体, 可以将所有的属性设置Public set/get. 由你来决定是否全面实施DDD.
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### IBookAppService接口
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在ABP中应用程序服务应该实现`IApplicationService接口`. 推荐每个应用程序服务创建一个接口:
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````csharp
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public interface IBookAppService : IApplicationService
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{
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Task CreateAsync(CreateBookDto input);
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}
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````
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我们将实现Create方法作为示例. CreateBookDto定义如下:
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```csharp
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public class CreateBookDto
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{
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[Required]
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[StringLength(Book.MaxNameLength)]
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public string Name { get; set; }
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public BookType Type { get; set; }
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public float? Price { get; set; }
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}
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```
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有关DTO更的教程,请参见[数据传输对象文档](Entities.md)
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### BookAppService(实现)
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````csharp
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public class BookAppService : ApplicationService, IBookAppService
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{
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private readonly IRepository<Book, Guid> _bookRepository;
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public BookAppService(IRepository<Book, Guid> bookRepository)
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{
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_bookRepository = bookRepository;
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}
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public async Task CreateAsync(CreateBookDto input)
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{
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var book = new Book(
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GuidGenerator.Create(),
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input.Name,
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input.Type,
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input.Price
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);
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await _bookRepository.InsertAsync(book);
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}
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}
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````
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* `BookAppService`继承了基类`ApplicationService`· 这不是必需的, 但是`ApplicationService`提供了应用服务常见的需求(比如本示例服务中使用的`GuidGenerator`). 如果不继承它, 我们需要在服务中手动注入`IGuidGenerator`(参见[Guid生成](Guid-Generation.md)文档)
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* `BookAppService`按照预期实现了`IBookAppService`
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* `BookAppService` 注入了 `IRepository<Book, Guid>`(请参见[仓储](Repositories.md))在CreateAsync方法内部使用仓储将新实体插入数据库.
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* `CreateAsync`使用`Book`实体的构造函数从给定的Input值创建新的`Book`对象
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### 数据传输对象
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应用服务使用并返回DTO而不是实体. ABP不会强制执行此规则. 但是将实体暴露给表示层(或远程客户端)存在重大问题, 所以不建议返回实体.
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有关更多信息, 请参见[DTO文档](Entities.md).
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### 对象到对象映射
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`CreateBook`方法使用参数`CreateBookDto`对象手动创建`Book`实体. 因为`Book`实体的构造函数强制执行(我们是这样设计的).
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但是在很多情况下使用**自动对象映射**从相似对象设置对象的属性更加方便实用. ABP提供了一个[对象到对象映射](Object-To-Object-Mapping.md)基础设施,使其变得更加容易.
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让我们创建另一种获取`Book`的方法. 首先,在`IBookAppService`接口中定义方法:
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````csharp
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public interface IBookAppService : IApplicationService
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{
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Task CreateAsync(CreateBookDto input);
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Task<BookDto> GetAsync(Guid id); //New method
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}
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````
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`BookDto`是一个简单的[DTO](Data-Transfer-Objects.md)类, 定义如下:
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````csharp
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[AutoMapFrom(typeof(Book))] //Defines the mapping
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public class BookDto
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{
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public Guid Id { get; set; }
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public string Name { get; set; }
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public BookType Type { get; set; }
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public float? Price { get; set; }
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}
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````
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* `BookDto`定义了`[AutoMapFrom(typeof(Book))]`属性来从创建对象映射Book到BookDto.
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然后你可以实现`GetAsync`方法. 如下所示:
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````csharp
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public async Task<BookDto> GetAsync(Guid id)
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{
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var book = await _bookRepository.GetAsync(id);
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return book.MapTo<BookDto>();
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}
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````
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`MapTo`扩展方法通过复制具有相同命名的所有属性将`Book`对象转换为`BookDto`对象.
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`MapTo`的另一种替代方法是使用`IObjectMapper`服务:
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````csharp
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public async Task<BookDto> GetAsync(Guid id)
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{
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var book = await _bookRepository.GetAsync(id);
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return ObjectMapper.Map<Book, BookDto>(book);
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}
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````
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虽然第二种语法编写起来有点困难,但是如果你编写单元测试,它会更好地工作.
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有关更多信息,请参阅[对象到对象映射](Object-To-Object-Mapping)文档.
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### 验证
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自动验证应用服务方法的输入(如ASP.NET Core 控制器的actions). 你可以使用标准数据注释属性或自定义验证方法来执行验证. ABP还确保输入不为空.
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请参阅[验证](Validation.md)文档了解更多信息.
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### 授权
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可以对应用程序服务方法使用声明性和命令式授权.
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请参阅[授权](Authorization.md)文档了解更多信息.
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### CRUD应用服务
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如果需要创建具有Create,Update,Delete和Get方法的简单CRUD应用服务,则可以使用ABP的基类轻松构建服务. 你可以继承CrudAppService或 AsyncCrudAppService.
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示例:
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创建继承`IAsyncCrudAppService`接口的`IBookAppService`接口.
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````csharp
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public interface IBookAppService :
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IAsyncCrudAppService< //Defines CRUD methods
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BookDto, //Used to show books
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Guid, //Primary key of the book entity
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PagedAndSortedResultRequestDto, //Used for paging/sorting on getting a list of books
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CreateUpdateBookDto, //Used to create a new book
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CreateUpdateBookDto> //Used to update a book
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{
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}
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````
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* IAsyncCrudAppService有泛型参数来获取实体的主键类型和CRUD操作的DTO类型(它不获取实体类型,因为实体类型未向客户端公开使用此接口).
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`IAsyncCrudAppService`声明以下方法:
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````csharp
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public interface IAsyncCrudAppService<
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TEntityDto,
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in TKey,
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in TGetListInput,
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in TCreateInput,
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in TUpdateInput>
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: IApplicationService
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where TEntityDto : IEntityDto<TKey>
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{
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Task<TEntityDto> GetAsync(TKey id);
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Task<PagedResultDto<TEntityDto>> GetListAsync(TGetListInput input);
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Task<TEntityDto> CreateAsync(TCreateInput input);
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Task<TEntityDto> UpdateAsync(TKey id, TUpdateInput input);
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Task DeleteAsync(TKey id);
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}
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````
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示例中使用的DTO类是`BookDto`和`CreateUpdateBookDto`:
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````csharp
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[AutoMapFrom(typeof(Book))]
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public class BookDto : AuditedEntityDto<Guid>
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{
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public string Name { get; set; }
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public BookType Type { get; set; }
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public float Price { get; set; }
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}
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[AutoMapTo(typeof(Book))]
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public class CreateUpdateBookDto
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{
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[Required]
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[StringLength(128)]
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public string Name { get; set; }
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[Required]
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public BookType Type { get; set; } = BookType.Undefined;
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[Required]
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public float Price { get; set; }
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}
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````
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* `CreateUpdateBookDto`由创建和更新操作共享,但你也可以使用单独的DTO类.
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最后`BookAppService`实现非常简单:
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````csharp
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public class BookAppService :
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AsyncCrudAppService<Book, BookDto, Guid, PagedAndSortedResultRequestDto,
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CreateUpdateBookDto, CreateUpdateBookDto>,
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IBookAppService
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{
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public BookAppService(IRepository<Book, Guid> repository)
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: base(repository)
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{
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}
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}
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````
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`AsyncCrudAppService`实现了`IAsyncCrudAppService`接口中声明的所有方法. 然后,你可以添加自己的自定义方法或覆盖和自定义实现.
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### 生命周期
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应用服务的生命周期是[transient](Dependency-Injection)的，它们会自动注册到依赖注入系统.
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