WebApi2官网学习记录---Attribute Routing

从WebApi 1迁移到WebAPI 2要改变配置代码如下：

WebApi 1：

protected void Application_Start()
{
    // WARNING - Not compatible with attribute routing.
    WebApiConfig.Register(GlobalConfiguration.Configuration);
}

WebAPI 2：

protected void Application_Start()
{
    // Pass a delegate to the Configure method.
    GlobalConfiguration.Configure(WebApiConfig.Register);
}

添加一个Route Attributes

public class OrdersController : ApiController
{
    [Route("customers/{customerId}/orders")]
    [HttpGet]
    public IEnumerable<Order> FindOrdersByCustomer(int customerId) { ... }
}

可以匹配一下URL：

• http://localhost/customers/1/orders
• http://localhost/customers/bob/orders
• http://localhost/customers/1234-5678/orders

匹配http post请求的CreateBook

[Route("api/books")]
[HttpPost]
public HttpResponseMessage CreateBook(Book book) { ... }

[Route("api/books")]
[AcceptVerbs("MKCOL")]
public void MakeCollection() { 

Route Prefixes

对于同一个controller路由有相同的前缀， 此时可以使用 [RoutePrefix] attribute

[RoutePrefix("api/books")]
public class BooksController : ApiController
{
    // GET api/books
    [Route("")]
    public IEnumerable<Book> Get() { ... }

    // GET api/books/5
    [Route("{id:int}")]
    public Book Get(int id) { ... }

    // POST api/books
    [Route("")]
    public HttpResponseMessage Post(Book book) { ... }
}

可以在方法的attribute中使用（~）重写路由前缀

[RoutePrefix("api/books")]
public class BooksController : ApiController
{
    // GET /api/authors/1/books
    [Route("~/api/authors/{authorId:int}/books")]
    public IEnumerable<Book> GetByAuthor(int authorId) { ... }

    // ...
}

路由前缀中可以包含参数

[RoutePrefix("customers/{customerId}")]
public class OrdersController : ApiController
{
    // GET customers/1/orders
    [Route("orders")]
    public IEnumerable<Order> Get(int customerId) { ... }
}

路由约束

  路由约束用于严格匹配路由中的参数，通用语法是{参数:约束}，如下：

[Route("users/{id:int}"]
public User GetUserById(int id) { ... }

[Route("users/{name}"]
public User GetUserByName(string name) { ... }

支持的约束如下表所示：

注意：带括号的约束，如"min"，可以对路由中的参数应用多个约束，用冒号分割约束

[Route("users/{id:int:min(1)}")]
public User GetUserById(int id) { ... }

 自定义路由约束

public class NonZeroConstraint : IHttpRouteConstraint
{
    public bool Match(HttpRequestMessage request, IHttpRoute route, string parameterName,
        IDictionary<string, object> values, HttpRouteDirection routeDirection)
    {
        object value;
        if (values.TryGetValue(parameterName, out value) && value != null)
        {
            long longValue;
            if (value is long)
            {
                longValue = (long)value;
                return longValue != 0;
            }

            string valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
            if (Int64.TryParse(valueString, NumberStyles.Integer,
                CultureInfo.InvariantCulture, out longValue))
            {
                return longValue != 0;
            }
        }
        return false;
    }
}

修改WebAPIConfig.cs
public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        var constraintResolver = new DefaultInlineConstraintResolver();
        constraintResolver.ConstraintMap.Add("nonzero", typeof(NonZeroConstraint));

        config.MapHttpAttributeRoutes(constraintResolver);
    }
}

实际应用：
[Route("{id:nonzero}")]
public HttpResponseMessage GetNonZero(int id) { ... }

可选的URI参数和默认值

第一种方式，默认值直接分配给了方法参数，因此参数获得的是精确的值

第二种方式，默认值通过model-binding进行处理，默认的model-binder将字符串类型的默认值"1033"转为int形的1033，对于model-binder可能有所不同。

 1 第一种写法
 2 public class BooksController : ApiController
 3 {
 4     [Route("api/books/locale/{lcid:int?}")]
 5     public IEnumerable<Book> GetBooksByLocale(int lcid = 1033) { ... }
 6 }
 7
 8 第二种写法
 9 public class BooksController : ApiController
10 {
11     [Route("api/books/locale/{lcid:int=1033}")]
12     public IEnumerable<Book> GetBooksByLocale(int lcid) { ... }
13 }

Route Names

web api中每个路由有一个name，Route names可以用来生成links

 1 public class BooksController : ApiController
 2 {
 3     [Route("api/books/{id}", Name="GetBookById")]
 4     public BookDto GetBook(int id)
 5     {
 6         // Implementation not shown...
 7     }
 8
 9     [Route("api/books")]
10     public HttpResponseMessage Post(Book book)
11     {
12         // Validate and add book to database (not shown)
13
14         var response = Request.CreateResponse(HttpStatusCode.Created);
15
16         // Generate a link to the new book and set the Location header in the response.
17         string uri = Url.Link("GetBookById", new { id = book.BookId });
18         response.Headers.Location = new Uri(uri);
19         return response;
20     }
21 }

Route Order

通过设置RouteOrder属性在route attribute上，可以指定Route的顺序，值越小先被计算，默认顺序对应的值是0

路由顺序的选择：

• 比较RouteOrder属性
• 对于URI部分按如下进行排序

1. URI的固定部分（literal segments）　　
2. 带约束的路由参数
3. 不带约束的路由参数
4. 带约束的通配符
5. 不带约束的通配符

• route的排序不区分大小写的

[RoutePrefix("orders")]
public class OrdersController : ApiController
{
    [Route("{id:int}")] // constrained parameter
    public HttpResponseMessage Get(int id) { ... }

    [Route("details")]  // literal
    public HttpResponseMessage GetDetails() { ... }

    [Route("pending", RouteOrder = 1)]
    public HttpResponseMessage GetPending() { ... }

    [Route("{customerName}")]  // unconstrained parameter
    public HttpResponseMessage GetByCustomer(string customerName) { ... }

    [Route("{*date:datetime}")]  // wildcard
    public HttpResponseMessage Get(DateTime date) { ... }
}

路由排序如下：

1. orders/{details}
2. orders/{id}
3. orders/{customreName}
4. orders/{*date}
5. orders/pending