APP
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();
}
本文摘自 ：https://blog.51cto.com/u
