《ASP.ENT Core 与 RESTful API 开发实战》-- (第5章)-- 读书笔记(下)
2021-10-22 16:48:54


第 5 章 使用 Entity Framework Core

5.4 重构 Controller 和 Action

重构 AuthorController

构造函数重构

public IMapper Mapper { get; set; }
public IRepositoryWrapper RepositoryWrapper { get; set; }

public AuthorController(IRepositoryWrapper repositoryWrapper, IMapper mapper)
{
RepositoryWrapper = repositoryWrapper;
Mapper = mapper;
}


IRepositoryWrapper 用于操作仓储类,IMapper 用于处理对象之间的映射关系

获取作者列表重构

[HttpGet]
public async Task<ActionResult<List<AuthorDto>>> GetAuthorsAsync()
{
var authors = (await RepositoryWrapper.Author.GetAllAsync()).OrderBy(author => author.Name);
var authorDtoList = Mapper.Map<IEnumerable<AuthorDto>>(authors);

return authorDtoList.ToList();
}


在 RepositoryBase 类中使用的延迟执行会在程序运行到 Mapper.Map 时才实际去执行查询,获取单个资源的方法的重构思路类似

创建资源方法重构

[HttpPost]
public async Task<IActionResult> CreateAuthorAsync(AuthorForCreationDto authorForCreationDto)
{
var author = Mapper.Map<Author>(authorForCreationDto);

RepositoryWrapper.Author.Create(author);
var result = await RepositoryWrapper.Author.SaveAsync();
if (!result)
{
throw new Exception("创建资源 author 失败");
}

var authorCreated = Mapper.Map<AuthorDto>(author);

// 返回201 Created 状态码,并在响应消息头中包含 Location 项,它的值是新创建资源的 URL
// 第一个参数是要调用 Action 的路由名称
// 第二个参数是包含要调用 Action 所需要参数的匿名对象
// 最后一个参数是代表添加成功后的资源本身
return CreatedAtRoute(nameof(GetAuthorsAsync), new { authorId = authorCreated.Id }, authorCreated);
}


当数据发生变化时,EF Core 会将实体对象的属性及其状态修改,只有在调用 DbContext 类的 Save 或 SaveAsync 方法后,所有的修改才会存储到数据库中

删除资源方法重构

[HttpDelete("{authorId}")]
public async Task<ActionResult> DeleteAuthorAsync(Guid authorId)
{
var author = await RepositoryWrapper.Author.GetByIdAsync(authorId);
if (author == null)
{
return NotFound();
}

RepositoryWrapper.Author.Delete(author);
var result = await RepositoryWrapper.Author.SaveAsync();
if (!result)
{
throw new Exception("删除资源 author 失败");
}

return NoContent();
}


重构 BookController

由于所有 Action 操作都基于一个存在的 Author 资源,因此每个 Action 中都会包含 IsExistAsync 逻辑,因此可以放在自定义过滤器中

namespace Library.API.Filters
{
public class CheckAuthorExistFilterAttribute : ActionFilterAttribute
{
public IRepositoryWrapper RepositoryWrapper { get; set; }

public CheckAuthorExistFilterAttribute(IRepositoryWrapper repositoryWrapper)
{
RepositoryWrapper = repositoryWrapper;
}

public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
var authorIdParameter = context.ActionArguments.Single(m => m.Key == "authorId");
Guid authorId = (Guid) authorIdParameter.Value;

var isExist = await RepositoryWrapper.Author.IsExistAsync(authorId);
if (!isExist)
{
context.Result = new NotFoundResult();
}

await base.OnActionExecutionAsync(context, next);
}
}
}


如果检查结果不存在,则结束本次请求,并返回 404 Not Found 状态码;反之,则继续完成 MVC 请求

接着,在 ConfigureServices 中注入

services.AddScoped<CheckAuthorExistFilterAttribute>();


注入之后可以在 BookController 中通过特性应用

[ServiceFilter(typeof(CheckAuthorExistFilterAttribute))]
public class BookController : ControllerBase


获取指定作者的所有图书,可以这么写

var books = await RepositoryWrapper.Book.GetByConditionAsync(book => book.Id == authorId);


但是更推荐在 IBookRepository 中定义专门的接口

Task<IEnumerable<Book>> GetBooksAsync(Guid authorId);


并在 BookRepository 中实现

public Task<IEnumerable<Book>> GetBooksAsync(Guid authorId)
{
return Task.FromResult(DbContext.Set<Book>().Where(book => book.AuthorId == authorId).AsEnumerable());
}


在 BookController 中重构 GetBooks

[HttpGet]
public async Task<ActionResult<List<BookDto>>> GetBooksAsync(Guid authorId)
{
var books = await RepositoryWrapper.Book.GetBooksAsync(authorId);
var bookDtoList = Mapper.Map<IEnumerable<BookDto>>(books);

return bookDtoList.ToList();
}


重构 GetBook 方法与此类似

Task<Book> GetBookAsync(Guid authorId, Guid bookId);

public async Task<Book> GetBookAsync(Guid authorId, Guid bookId)
{
return await DbContext.Set<Book>()
.SingleOrDefaultAsync(book => book.AuthorId == authorId && book.Id == bookId);
}

[HttpGet("{bookId}", Name = nameof(GetBookAsync))]
public async Task<ActionResult<BookDto>> GetBookAsync(Guid authorId, Guid bookId)
{
var book = await RepositoryWrapper.Book.GetBookAsync(authorId, bookId);
if (book == null)
{
return NotFound();
}

var bookDto = Mapper.Map<BookDto>(book);
return bookDto;
}


当添加一个子级资源,将 BookForCreationDto 对象映射为 Book 后,还需要为其 AuthorId 属性设置值,否则创建失败

[HttpPost]
public async Task<IActionResult> AddBookAsync(Guid authorId, BookForCreationDto bookForCreationDto)
{
var book = Mapper.Map<Book>(bookForCreationDto);
book.AuthorId = authorId;
RepositoryWrapper.Book.Create(book);
if (!await RepositoryWrapper.Book.SaveAsync())
{
throw new Exception("创建资源 Book 失败");
}

var bookDto = Mapper.Map<BookDto>(book);
return CreatedAtRoute(nameof(GetBookAsync), new {bookId = bookDto.Id}, bookDto);
}


对于更新子级资源或部分更新子级资源,处了检查父级、子级资源是否存在外,还应该使用 IMapper 接口中的 Map 方法的另一个重载

object Map(object source, object destination, Type sourceType, Type destinationType);


它能将源映射到一个已经存在的对象,重载是为了将 BookForUpdateDto 映射到已经从数据库中获取到的 Book 实体

[HttpPut("{bookId}")]
public async Task<IActionResult> UpdateBookAsync(Guid authorId, Guid bookId, BookForUpdateDto updateBook)
{
var book = await RepositoryWrapper.Book.GetBookAsync(authorId, bookId);
if (book == null)
{
return NotFound();
}

Mapper.Map(updateBook, book, typeof(BookForUpdateDto), typeof(Book));
RepositoryWrapper.Book.Update(book);
if (!await RepositoryWrapper.Book.SaveAsync())
{
throw new Exception("更新资源 Book 失败");
}

return NoContent();
}


部分更新的实现逻辑与此类似,不同的是获取需要部分更新的 Book 实体后,首先将它映射为 BookForUpdateDto 类型的对象,其次使用 JsonPatchDocument 的 ApplyTo 方法将更新信息应用到映射后的 BookForUpdateDto 对象,接着再将它映射到 Book 实体得到更新后的值

[HttpPatch("{bookId}")]
public async Task<IActionResult> PartiallyUpdateBookAsync(Guid authorId, Guid bookId, JsonPatchDocument<BookForUpdateDto> patchDocument)
{
var book = await RepositoryWrapper.Book.GetBookAsync(authorId, bookId);
if (book == null)
{
return NotFound();
}

var bookUpdateDto = Mapper.Map<BookForUpdateDto>(book);
patchDocument.ApplyTo(bookUpdateDto, ModelState);
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}

Mapper.Map(bookUpdateDto, book, typeof(BookForUpdateDto), typeof(Book));

RepositoryWrapper.Book.Update(book);
if (!await RepositoryWrapper.Book.SaveAsync())
{
throw new Exception("更新资源 Book 失败");
}

return NoContent();
}


《ASP.ENT Core 与 RESTful API 开发实战》-- (第5章)-- 读书笔记(下)_构造函数


本文摘自 :https://blog.51cto.com/u


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