Restful几乎已算是API设计的标准,通过HTTP Method区分新增(Create)、查询(Read)、修改(Update)和删除(Delete),简称CRUD四种数据存取方式,简约又直接的风格,让人用的爱不释手。
本篇将介绍如何通过 Core实践REST-Like API。
为什么是REST-Like 而不是 REST?
本文API设计未符合HATEOAS(Hypermedia As The Engine Of Application State)原则,所以不得称为RESTful API。
RESTful API 有四个重要的原则要遵守:
Level 0
使用HTTP做为资料传输的媒介。Level 1
不要提供一个包山包海的API,而是要区分资源,每个资源都该有对应的API。Level 2
透过HTTP Method区分新增(Create)、查询(Read)、修改(Update)跟删除(Delete)。Level 3
对同资源可以用链结表达的方式,向下延伸查询或修改。
参考:HATEOAS
HTTP Method
REST-Like API 对数据的操作行为,通过HTTP Method 分为以下四种方式:
新增(Create)
用HTTPPOST
通过Body传递JSON或XML格式的数据给Server。例如:
POST http://localhost:5000/api/users{"id": 1,"name": "SnailDev"}
查询(Read)
用HTTPGET通
过URL带查询参数。通常查询单一资源会用路由参数(Routing Parameter)带上唯一值(Primary Key);多笔查询会用复数,而查询条件用Query String。例如:
# 单笔查询GET http://localhost:5000/api/users/1# 多笔查询GET http://localhost:5000/api/users# 多笔查询带条件GET http://localhost:5000/api/users?q=SnailDev
修改(Update)
修改数据如同查询跟新增的组合,用HTTPPUT通
过URL带路由参数,找到要修改的目标;再通过Body传递JSON或XML格式的数据给Server。例如:
PUT http://localhost:5000/api/users/1{"name": "SnailDev"}
删除(Delete)
删除数据同查询,用HTTPDELETE
通过URL带路由参数,找到要删除的目标。例如:
DELETE http://localhost:5000/api/users/1
HTTP Method Attribute
Core 2 学习笔记(六)MVC有提到,过去 MVC把MVC及Web API的套件分开,但在 Core中MVC及Web API用的套件是相同的。所以只要装Microsoft.AspNetCore.Mvc
套件就可以用Web API了。路由方式也跟 Core 2 学习笔记(七)路由介绍的RouteAttribute
差不多,只是改用HTTP Method Attribute。
HTTP Method Attribute 符合RESTful 原则的路由设定方式如下:
[Route("api/[controller]s")]public class UserController : Controller{[HttpGet]public List<UserModel> Get(string q){// ...}[HttpGet("{id}")]public UserModel Get(int id){// ...}[HttpPost]public int Post([FromBody]UserModel user){// ...}[HttpPut("{id}")]public void Put(int id, [FromBody]UserModel user){// ...}[HttpDelete("{id}")]public void Delete(int id){// ...}}
目前 Core 还没有像 MVC 的MapHttpAttributeRoutes 可以绑Http Method 的全局路由,都要在Action 加上HTTP Method Attribute。
SerializerSettings
用以下代码,说明SerializerSettings
:
public class UserModel{public int Id { get; set; }public string Name { get; set; }public string Email { get; set; } public string PhoneNumber { get; set; }public string Address { get; set; }}// ...[Route("api/[controller]s")]public class UserController : Controller{[HttpGet("{id}")]public UserModel Get(int id){return new UserModel {Id = 1,Name = "SnailDev"};}}
camel Case
过去 Web API 2预设是Pascal Case;而 Core预设是使用camel Case。
若想要指定用ContractResolver
,可以在Startup.cs
的ConfigureServices
加入MVC服务时,使用AddJsonOptions
设定如下:
// ...public class Startup{public void ConfigureServices(IServiceCollection services){ services.AddMvc().AddJsonOptions(options => {options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();});// 同以下写法:// services.AddMvc();}}
访问http://localhost:5000/api/users/1
会返回JSON如下:
{"id": 1,"name": "SnailDev","email": null,"phoneNumber": null,"address": null}
Pascal Case
若想保持跟 Web API 2一样使用Pascal Case,ContractResolver
则改用DefaultContractResolver
。
// ...public class Startup{public void ConfigureServices(IServiceCollection services){ services.AddMvc().AddJsonOptions(options => {options.SerializerSettings.ContractResolver = new DefaultContractResolver();});}}
DefaultContractResolver
名称是延续,虽然名称叫Default,但在 Core它不是Default。CamelCasePropertyNamesContractResolver
才是 Core的DefaultContractResolver。
访问http://localhost:5000/api/users/1
会返回JSON如下:
{"Id": 1,"Name": "SnailDev","Email": null,"PhoneNumber": null,"Address": null}
Ignore Null
上述两个JSON 回传,都带有null 的字段。在序列化的过程,找不到字段会自动转成null,传送的过程忽略掉也没错,反而可以节省到一点流量。
// ...public class Startup{public void ConfigureServices(IServiceCollection services){ services.AddMvc().AddJsonOptions(options => {options.SerializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;});}}
访问http://localhost:5000/api/users/1
会返回JSON如下:
{"id": 1,"name": "SnailDev"}
示例程序
Startup.cs
public class Startup{public void ConfigureServices(IServiceCollection services){services.AddMvc().AddJsonOptions(options => {options.SerializerSettings.NullValueHandling= Newtonsoft.Json.NullValueHandling.Ignore;});}public void Configure(IApplicationBuilder app){app.UseMvc();}}
Models\ResultModel.cs
namespace MyWebsite.Models{public class ResultModel{public bool IsSuccess { get; set; }public string Message { get; set; }public object Data { get; set; }}}
用一个ResultModel 来包装每个API 回传的内容,不论调用Web API 成功失败都用此对象包装,避免直接throw exception 到Client,产生HTTP Status 200 以外的状态。
Controllers/UserController.cs
using System.Collections.Generic;using System.Linq;using System.Text.RegularExpressions;using Microsoft.AspNetCore.Mvc;using MyWebsite.Models;namespace MyWebsite.Controllers{[Route("api/[controller]s")]public class UserController : Controller{private static List<UserModel> _users = new List<UserModel>();[HttpGet]public ResultModel Get(string q){var result = new ResultModel();result.Data = _users.Where(c => string.IsNullOrEmpty(q) || Regex.IsMatch(c.Name, q, RegexOptions.IgnoreCase));result.IsSuccess = true;return result;}[HttpGet("{id}")]public ResultModel Get(int id){var result = new ResultModel();result.Data = _users.SingleOrDefault(c => c.Id == id);result.IsSuccess = true;return result;}[HttpPost]public ResultModel Post([FromBody]UserModel user){var result = new ResultModel();user.Id = _users.Count() == 0 ? 1 : _users.Max(c => c.Id) + 1;_users.Add(user);result.Data = user.Id;result.IsSuccess = true;return result;}[HttpPut("{id}")]public ResultModel Put(int id, [FromBody]UserModel user){var result = new ResultModel();int index;if ((index = _users.FindIndex(c => c.Id == id)) != -1){_users[index] = user;result.IsSuccess = true;}return result;}[HttpDelete("{id}")]public ResultModel Delete(int id){var result = new ResultModel();int index;if ((index = _users.FindIndex(c => c.Id == id)) != -1){_users.RemoveAt(index);result.IsSuccess = true;}return result;}}}
执行结果
通过Postman 测试API。
新增(Create)查询(Read)修改(Update)删除(Delete)
参考
Routing in Core
Attribute Routing in Core
Richardson Maturity Model
HATEOAS
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