Asp.NetCoreWebApi - RESTful Api

发布时间：2020-12-16 06:28:20 所属栏目：asp.Net 来源：网络整理

导读：REST 常用http动词 WebApi 在 Asp.NetCore 中的实现 3.1. 创建WebApi项目. 3.2. 集成Entity Framework Core操作Mysql 3.2.1. 安装相关的包(为Xxxx.Infrastructure项目安装) 3.2.2. 建立Entity和Context 3.2.3. ConfigureService中注入EF服务 3.2.4. 迁移数据

1. REST
1. 常用http动词
1. WebApi 在 Asp.NetCore 中的实现
- 3.1. 创建WebApi项目.
- 3.2. 集成Entity Framework Core操作Mysql
  - 3.2.1. 安装相关的包(为Xxxx.Infrastructure项目安装)
  - 3.2.2. 建立Entity和Context
  - 3.2.3. ConfigureService中注入EF服务
  - 3.2.4. 迁移数据库
  - 3.2.5. 数据库迁移结果
  - 3.2.6. 为数据库创建种子数据
1. 支持https
1. 支持HSTS
1. 使用SerilLog
- 6.1. 安装nuget包
- 6.2. 添加代码
- 6.3. 自行测试
1. Asp.NetCore配置文件
- 7.1. 默认配置文件
- 7.2. 获得配置
1. 自定义一个异常处理,ExceptionHandler
- 8.1. 弄一个类,写一个扩展方法处理异常
- 8.2. 在Configuration中使用扩展方法
1. 实现数据接口类(Resource),使用AutoMapper在Resource和Entity中映射
- 9.1. 为Entity类创建对应的Resource类
- 9.2. 使用 AutoMapper
1. 使用FluentValidation
- 10.1. 安装Nuget包
- 10.2. 为每一个Resource配置验证器
1. 实现Http Get(翻页,过滤,排序)
- 11.1. 资源命名
  - 11.1.1. 资源应该使用名词,例
  - 11.1.2. 资源命名层次结构
- 11.2. 内容协商
1. 翻页
- 12.1. 构造翻页请求参数类
- 12.2. Repository实现支持翻页请求参数的方法
- 12.3. 搜索(过滤)
- 12.4. 排序
  - 12.4.1. 排序思路
1. 资源塑形(Resource shaping)
1. HATEOAS
- 14.1. 创建供应商特定媒体类型
  - 14.1.1. 判断Media Type类型

参考 :

ASP.NET Core Web API 开发-RESTful API实现

理解HTTP幂等性

某站微软Mvp杨旭的Asp.NetCore WebApi的视频

1. REST

REST : 具象状态传输(Representational State Transfer,简称REST),是Roy Thomas Fielding博士于2000年在他的博士论文 "Architectural Styles and the Design of Network-based Software Architectures" 中提出来的一种万维网软件架构风格。
目前在三种主流的Web服务实现方案中，因为REST模式与复杂的SOAP和XML-RPC相比更加简洁，越来越多的web服务开始采用REST风格设计和实现。例如，Amazon.com提供接近REST风格的Web服务执行图书查询；

符合REST设计风格的Web API称为RESTful API。它从以下三个方面资源进行定义：

直观简短的资源地址：URI，比如：http://example.com/resources/ .
传输的资源：Web服务接受与返回的互联网媒体类型，比如：JSON，XML，YAML等...
对资源的操作：Web服务在该资源上所支持的一系列请求方法（比如：POST，GET，PUT或DELETE）.

PUT和DELETE方法是幂等方法.GET方法是安全方法（不会对服务器端有修改，因此当然也是幂等的）.

ps 关于幂等方法 :
看这篇理解HTTP幂等性.
简单说,客户端多次请求服务端返回的结果都相同,那么就说这个操作是幂等的.(个人理解,详细的看上面给的文章)

不像基于SOAP的Web服务，RESTful Web服务并没有“正式”的标准。这是因为REST是一种架构，而SOAP只是一个协议。虽然REST不是一个标准，但大部分RESTful Web服务实现会使用HTTP、URI、JSON和XML等各种标准。

2. 常用http动词

括号中是相应的SQL命令.

GET(SELECT) : 从服务器取出资源(一项或多项).
POST(CREATE) : 在服务器新建一个资源.
PUT(UPDATE) : 在服务器更新资源(客户端提供改变后的完整资源).
PATCH(UPDATE) : 在服务器更新资源(客户端提供改变的属性).
DELETE(DELETE) : 在服务器删除资源.

3. WebApi 在 Asp.NetCore 中的实现

这里以用户增删改查为例.

3.1. 创建WebApi项目.

参考ASP.NET Core WebAPI 开发-新建WebAPI项目.

注意,本文建立的Asp.NetCore WebApi项目选择.net core版本是2.2,不建议使用其他版本,2.1版本下会遇到依赖文件冲突问题!所以一定要选择2.2版本的.net core.

3.2. 集成Entity Framework Core操作Mysql

3.2.1. 安装相关的包(为Xxxx.Infrastructure项目安装)

Microsoft.EntityFrameworkCore.Design
Pomelo.EntityFrameworkCore.MySql

这里注意一下,Mysql官方的包是 MySql.Data.EntityFrameworkCore,但是这个包有bug,我在github上看到有人说有替代方案 - Pomelo.EntityFrameworkCore.MySql,经过尝试,后者比前者好用.所有这里就选择后者了.使用前者的话可能会导致数据库迁移失败(Update的时候).

PS: Mysql文档原文:

Install the MySql.Data.EntityFrameworkCore NuGet package.
For EF Core 1.1 only: If you plan to scaffold a database,install the MySql.Data.EntityFrameworkCore.Design NuGet package as well.

EFCore - MySql文档
Mysql版本要求:
Mysql版本要高于5.7
使用最新版本的Mysql Connector(2019 6/27 目前是8.x).

为Xxxx.Infrastructure项目安装EFCore相关的包:

为Xxxx.Api项目安装 Pomelo.EntityFrameworkCore.MySql

3.2.2. 建立Entity和Context

ApiUser

namespace ApiStudy.Core.Entities
{
    using System;

    public class ApiUser
    {
        public Guid Guid { get; set; }
        public string Name { get; set; }
        public string Passwd { get; set; }
        public DateTime RegistrationDate { get; set; }
        public DateTime Birth { get; set; }
        public string ProfilePhotoUrl { get; set; }
        public string PhoneNumber { get; set; }
        public string Email { get; set; }
    }
}

UserContext

namespace ApiStudy.Infrastructure.Database
{
    using ApiStudy.Core.Entities;
    using Microsoft.EntityFrameworkCore;

    public class UserContext:DbContext
    {
        public UserContext(DbContextOptions<UserContext> options): base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<ApiUser>().HasKey(u => u.Guid);

            base.OnModelCreating(modelBuilder);
        }

        public DbSet<ApiUser> ApiUsers { get; set; }
    }
}

3.2.3. ConfigureService中注入EF服务

services.AddDbContext<UserContext>(options =>
            {
                string connString = "Server=Xxx:xxx:xxx:xxx;Database=Xxxx;Uid=root;Pwd=Xxxxx; ";
                options.UseMySQL(connString);
            });

3.2.4. 迁移数据库

在Tools > NuGet Package Manager > Package Manager Console输入命令.
Add-Migration Xxx 添加迁移.
PS : 如果迁移不想要,使用 Remove-Migration 命令删除迁移.
Update-Database 更新到数据库.

3.2.5. 数据库迁移结果

3.2.6. 为数据库创建种子数据

写一个创建种子数据的类

UserContextSeed

namespace ApiStudy.Infrastructure.Database
{
    using ApiStudy.Core.Entities;
    using Microsoft.Extensions.Logging;
    using System;
    using System.Linq;
    using System.Threading.Tasks;

    public class UserContextSeed
    {
        public static async Task SeedAsync(UserContext context,ILoggerFactory loggerFactory)
        {
            try
            {
                if (!context.ApiUsers.Any())
                {
                    context.ApiUsers.AddRange(
                        new ApiUser
                        {
                            Guid = Guid.NewGuid(),Name = "la",Birth = new DateTime(1998,11,29),RegistrationDate = new DateTime(2019,6,28),Passwd = "123587",ProfilePhotoUrl = "https://www.laggage.top/",PhoneNumber = "10086",Email = "[email?protected]"
                        },new ApiUser
                        {
                            Guid = Guid.NewGuid(),Name = "David",Birth = new DateTime(1995,8,3,Passwd = "awt87495987",PhoneNumber = "1008611",Email = "[email?protected]"
                        },Birth = new DateTime(2001,19),4,25),Email = "[email?protected]"
                        },Name = "Linus",Birth = new DateTime(1999,10,26),RegistrationDate = new DateTime(2018,2,8),PhoneNumber = "17084759987",Email = "[email?protected]"
                        },Name = "YouYou",Birth = new DateTime(1992,1,RegistrationDate = new DateTime(2015,7,Passwd = "grwe874864987",Email = "[email?protected]"
                        },Name = "小白",Birth = new DateTime(1997,9,30),Passwd = "gewa749864",Email = "[email?protected]"
                        });

                    await context.SaveChangesAsync();
                }
            }
            catch(Exception ex)
            {
                ILogger logger = loggerFactory.CreateLogger<UserContextSeed>();
                logger.LogError(ex,"Error occurred while seeding database");
            }
        }
    }
}

修改Program.Main方法

Program.Main

IWebHost host = CreateWebHostBuilder(args).Build();

using (IServiceScope scope = host.Services.CreateScope())
{
    IServiceProvider provider = scope.ServiceProvider;
    UserContext userContext = provider.GetService<UserContext>();
    ILoggerFactory loggerFactory = provider.GetService<ILoggerFactory>();
    UserContextSeed.SeedAsync(userContext,loggerFactory).Wait();
}

host.Run();

这个时候运行程序会出现异常,打断点看一下异常信息:Data too long for column 'Guid' at row 1

可以猜到,Mysql的varbinary(16)放不下C# Guid.NewGuid()方法生成的Guid,所以配置一下数据库Guid字段类型为varchar(256)可以解决问题.

解决方案:
修改 UserContext.OnModelCreating 方法
配置一下 ApiUser.Guid 属性到Mysql数据库的映射:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<ApiUser>().Property(p => p.Guid)
        .HasColumnType("nvarchar(256)");
    modelBuilder.Entity<ApiUser>().HasKey(u => u.Guid);
    
    base.OnModelCreating(modelBuilder);
}

4. 支持https

将所有http请求全部映射到https

Startup中:
ConfigureServices方法注册,并配置端口和状态码等:
services.AddHttpsRedirection(…)

services.AddHttpsRedirection(options =>
                {
                    options.RedirectStatusCode = StatusCodes.Status307TemporaryRedirect;
                    options.HttpsPort = 5001;
                });

Configure方法使用该中间件:

app.UseHttpsRedirection()

5. 支持HSTS

ConfigureServices方法注册
看官方文档

services.AddHsts(options =>
{
    options.Preload = true;
    options.IncludeSubDomains = true;
    options.MaxAge = TimeSpan.FromDays(60);
    options.ExcludedHosts.Add("example.com");
    options.ExcludedHosts.Add("www.example.com");
});

Configure方法配置中间件管道

app.UseHsts();

注意 app.UseHsts() 方法最好放在 app.UseHttps() 方法之后.

6. 使用SerilLog

有关日志的微软官方文档

SerilLog github仓库
该github仓库上有详细的使用说明.

使用方法:

6.1. 安装nuget包

Serilog.AspNetCore
Serilog.Sinks.Console

6.2. 添加代码

Program.Main方法中:

Log.Logger = new LoggerConfiguration()
            .MinimumLevel.Debug()
            .MinimumLevel.Override("Microsoft",LogEventLevel.Information)
            .Enrich.FromLogContext()
            .WriteTo.Console()
            .CreateLogger();

修改Program.CreateWebHostBuilder(...)

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .UseSerilog(); // <-- Add this line;
 }

6.3. 自行测试

7. Asp.NetCore配置文件

7.1. 默认配置文件

默认 appsettings.json
ConfigurationBuilder().AddJsonFile("appsettings.json").Build()-->IConfigurationRoot(IConfiguration)

7.2. 获得配置

IConfiguration[“Key:ChildKey”]
针对”ConnectionStrings:xxx”,可以使用IConfiguration.GetConnectionString(“xxx”)

private static IConfiguration Configuration { get; set; }

public StartupDevelopment(IConfiguration config)
{
    Configuration = config;
}

...

Configuration[“Key:ChildKey”]

8. 自定义一个异常处理,ExceptionHandler

8.1. 弄一个类,写一个扩展方法处理异常

namespace ApiStudy.Api.Extensions
{
    using Microsoft.AspNetCore.Builder;
    using Microsoft.AspNetCore.Http;
    using Microsoft.Extensions.Logging;
    using System;

    public static class ExceptionHandlingExtensions
    {
        public static void UseCustomExceptionHandler(this IApplicationBuilder app,ILoggerFactory loggerFactory)
        {
            app.UseExceptionHandler(
                builder => builder.Run(async context =>
                {
                    context.Response.StatusCode = StatusCodes.Status500InternalServerError;
                    context.Response.ContentType = "application/json";

                    Exception ex = context.Features.Get<Exception>();
                    if (!(ex is null))
                    {
                        ILogger logger = loggerFactory.CreateLogger("ApiStudy.Api.Extensions.ExceptionHandlingExtensions");
                        logger.LogError(ex,"Error occurred.");
                    }
                    await context.Response.WriteAsync(ex?.Message ?? "Error occurred,but cannot get exception message.For more detail,go to see the log.");
                }));
        }
    }
}

8.2. 在Configuration中使用扩展方法

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app,ILoggerFactory loggerFactory)
{
    app.UseCustomExceptionHandler(loggerFactory);  //modified code

    //app.UseDeveloperExceptionPage();
    app.UseHsts();
    app.UseHttpsRedirection();

    app.UseMvc(); //使用默认路由
}

9. 实现数据接口类(Resource),使用AutoMapper在Resource和Entity中映射

9.1. 为Entity类创建对应的Resource类

ApiUserResource

namespace ApiStudy.Infrastructure.Resources
{
    using System;

    public class ApiUserResource
    {
        public Guid Guid { get; set; }
        public string Name { get; set; }
        //public string Passwd { get; set; }
        public DateTime RegistrationDate { get; set; }
        public DateTime Birth { get; set; }
        public string ProfilePhotoUrl { get; set; }
        public string PhoneNumber { get; set; }
        public string Email { get; set; }
    }
}

9.2. 使用 AutoMapper

添加nuget包
AutoMapper
AutoMapper.Extensions.Microsoft.DependencyInjection

配置映射
可以创建Profile
CreateMap<TSource,TDestination>()

MappingProfile

namespace ApiStudy.Api.Extensions
{
    using ApiStudy.Core.Entities;
    using ApiStudy.Infrastructure.Resources;
    using AutoMapper;
    using System;
    using System.Text;

    public class MappingProfile : Profile
    {
        public MappingProfile()
        {
            CreateMap<ApiUser,ApiUserResource>()
                .ForMember(
                d => d.Passwd,opt => opt.AddTransform(s => Convert.ToBase64String(Encoding.Default.GetBytes(s))));

            CreateMap<ApiUserResource,ApiUser>()
                .ForMember(
                d => d.Passwd,opt => opt.AddTransform(s => Encoding.Default.GetString(Convert.FromBase64String(s))));
        }
    }
}

注入服务
services.AddAutoMapper()

10. 使用FluentValidation

FluentValidation官网

10.1. 安装Nuget包

FluentValidation
FluentValidation.AspNetCore

10.2. 为每一个Resource配置验证器

继承于AbstractValidator

ApiUserResourceValidator

namespace ApiStudy.Infrastructure.Resources
{
    using FluentValidation;

    public class ApiUserResourceValidator : AbstractValidator<ApiUserResource>
    {
        public ApiUserResourceValidator()
        {
            RuleFor(s => s.Name)
                .MaximumLength(80)
                .WithName("用户名")
                .WithMessage("{PropertyName}的最大长度为80")
                .NotEmpty()
                .WithMessage("{PropertyName}不能为空!");
        }
    }
}

注册到容器:services.AddTransient<>()
services.AddTransient<IValidator<ApiUserResource>,ApiUserResourceValidator>();

11. 实现Http Get(翻页,排序)

基本的Get实现

[HttpGet]
public async Task<IActionResult> Get()
{
    IEnumerable<ApiUser> apiUsers = await _apiUserRepository.GetAllApiUsersAsync();

    IEnumerable<ApiUserResource> apiUserResources = 
        _mapper.Map<IEnumerable<ApiUser>,IEnumerable<ApiUserResource>>(apiUsers);

    return Ok(apiUserResources);
}

[HttpGet("{guid}")]
public async Task<IActionResult> Get(string guid)
{
    ApiUser apiUser = await _apiUserRepository.GetApiUserByGuidAsync(Guid.Parse(guid));

    if (apiUser is null) return NotFound();

    ApiUserResource apiUserResource = _mapper.Map<ApiUser,ApiUserResource>(apiUser);

    return Ok(apiUserResource);
}

11.1. 资源命名

11.1.1. 资源应该使用名词,例

api/getusers就是不正确的.
GET　api/users就是正确的

11.1.2. 资源命名层次结构

例如api/department/{departmentId}/emoloyees,这就表示了 department (部门)和员工
(employee)之前是主从关系.
而api/department/{departmentId}/emoloyees/{employeeId},就表示了该部门下的某个员
工.

11.2. 内容协商

ASP.NET Core支持输出和输入两种格式化器.

用于输出的media type放在Accept Header里,表示客户端接受这种格式的输出.
用于输入的media type放Content-Type Header里,表示客户端传进来的数据是这种格式.
ReturnHttpNotAcceptable设为true,如果客户端请求不支持的数据格式,就会返回406.
```
services.AddMvc(options =>
{
    options.ReturnHttpNotAcceptable = true;
});
```
支持输出XML格式:options.OutputFormatters.Add(newXmlDataContractSerializerOutputFormatter());

12. 翻页

12.1. 构造翻页请求参数类

QueryParameters

namespace ApiStudy.Core.Entities
{
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Runtime.CompilerServices;

    public abstract class QueryParameters : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        private const int DefaultPageSize = 10;
        private const int DefaultMaxPageSize = 100;

        private int _pageIndex = 1;
        public virtual int PageIndex
        {
            get => _pageIndex;
            set => SetField(ref _pageIndex,value);
        }

        private int _pageSize = DefaultPageSize;
        public virtual int PageSize
        {
            get => _pageSize;
            set => SetField(ref _pageSize,value);
        }

        private int _maxPageSize = DefaultMaxPageSize;
        public virtual int MaxPageSize
        {
            get => _maxPageSize;
            set => SetField(ref _maxPageSize,value);
        }

        public string OrderBy { get; set; }
        public string Fields { get; set; }

        protected void SetField<TField>(
            ref TField field,in TField newValue,[CallerMemberName] string propertyName = null)
        {
            if (EqualityComparer<TField>.Default.Equals(field,newValue))
                return;
            field = newValue;
            if (propertyName == nameof(PageSize) || propertyName == nameof(MaxPageSize)) SetPageSize();
            
            PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(propertyName));
            
        }

        private void SetPageSize()
        {
            if (_maxPageSize <= 0) _maxPageSize = DefaultMaxPageSize;
            if (_pageSize <= 0) _pageSize = DefaultPageSize;
            _pageSize = _pageSize > _maxPageSize ? _maxPageSize : _pageSize;
        }
    }
}

ApiUserParameters

namespace ApiStudy.Core.Entities
{
    public class ApiUserParameters:QueryParameters
    {
        public string UserName { get; set; }
    }
}

12.2. Repository实现支持翻页请求参数的方法

Repository相关代码

/*----- ApiUserRepository -----*/
public PaginatedList<ApiUser> GetAllApiUsers(ApiUserParameters parameters)
{
    return new PaginatedList<ApiUser>(
        parameters.PageIndex,parameters.PageSize,_context.ApiUsers.Count(),_context.ApiUsers.Skip(parameters.PageIndex * parameters.PageSize)
        .Take(parameters.PageSize));
}

public Task<PaginatedList<ApiUser>> GetAllApiUsersAsync(ApiUserParameters parameters)
{
    return Task.Run(() => GetAllApiUsers(parameters));
}

/*----- IApiUserRepository -----*/
PaginatedList<ApiUser> GetAllApiUsers(ApiUserParameters parameters);
Task<PaginatedList<ApiUser>> GetAllApiUsersAsync(ApiUserParameters parameters);

UserController部分代码

...

[HttpGet(Name = "GetAllApiUsers")]
public async Task<IActionResult> GetAllApiUsers(ApiUserParameters parameters)
{
    PaginatedList<ApiUser> apiUsers = await _apiUserRepository.GetAllApiUsersAsync(parameters);

    IEnumerable<ApiUserResource> apiUserResources = 
        _mapper.Map<IEnumerable<ApiUser>,IEnumerable<ApiUserResource>>(apiUsers);

    var meta = new
    {
        PageIndex = apiUsers.PageIndex,PageSize = apiUsers.PageSize,PageCount = apiUsers.PageCount,TotalItemsCount = apiUsers.TotalItemsCount,NextPageUrl = CreateApiUserUrl(parameters,ResourceUriType.NextPage),PreviousPageUrl = CreateApiUserUrl(parameters,ResourceUriType.PreviousPage)
    };
    Response.Headers.Add(
        "X-Pagination",JsonConvert.SerializeObject(
            meta,new JsonSerializerSettings
            { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
    return Ok(apiUserResources);
}

...

private string CreateApiUserUrl(ApiUserParameters parameters,ResourceUriType uriType)
{
    var param = new ApiUserParameters
    {
        PageIndex = parameters.PageIndex,PageSize = parameters.PageSize
    };
    switch (uriType)
    {
        case ResourceUriType.PreviousPage:
            param.PageIndex--;
            break;
        case ResourceUriType.NextPage:
            param.PageIndex++;
            break;
        case ResourceUriType.CurrentPage:
            break;
        default:break;
    }
    return Url.Link("GetAllApiUsers",parameters);
}

PS注意,为HttpGet方法添加参数的话,在.net core2.2版本下,去掉那个ApiUserController上的 [ApiController());] 特性,否则参数传不进来..net core3.0中据说已经修复这个问题.

12.3. 搜索(过滤)

修改Repository代码:

public PaginatedList<ApiUser> GetAllApiUsers(ApiUserParameters parameters)
{
    IQueryable<ApiUser> query = _context.ApiUsers.AsQueryable();
    query = query.Skip(parameters.PageIndex * parameters.PageSize)
            .Take(parameters.PageSize);

    if (!string.IsNullOrEmpty(parameters.UserName))
        query = _context.ApiUsers.Where(
            x => StringComparer.OrdinalIgnoreCase.Compare(x.Name,parameters.UserName) == 0);

    return new PaginatedList<ApiUser>(
        parameters.PageIndex,query.Count(),query);
}

12.4. 排序

12.4.1. 排序思路

需要安装System.Linq.Dynamic.Core

思路:

PropertyMappingContainer
- PropertyMapping(ApiUserPropertyMapping)
  - MappedProperty

MappedProperty

namespace ApiStudy.Infrastructure.Services
{
    public struct MappedProperty
    {
        public MappedProperty(string name,bool revert = false)
        {
            Name = name;
            Revert = revert;
        }

        public string Name { get; set; }
        public bool Revert { get; set; }
    }
}

IPropertyMapping

namespace ApiStudy.Infrastructure.Services
{
    using System.Collections.Generic;

    public interface IPropertyMapping
    {
        Dictionary<string,List<MappedProperty>> MappingDictionary { get; }
    }
}

PropertyMapping

namespace ApiStudy.Infrastructure.Services
{
    using System.Collections.Generic;

    public abstract class PropertyMapping<TSource,TDestination> : IPropertyMapping
    {
        public Dictionary<string,List<MappedProperty>> MappingDictionary { get; }

        public PropertyMapping(Dictionary<string,List<MappedProperty>> MappingDict)
        {
            MappingDictionary = MappingDict;
        }
    }
}

IPropertyMappingContainer

namespace ApiStudy.Infrastructure.Services
{
    public interface IPropertyMappingContainer
    {
        void Register<T>() where T : IPropertyMapping,new();
        IPropertyMapping Resolve<TSource,TDestination>();
        bool ValidateMappingExistsFor<TSource,TDestination>(string fields);
    }
}

PropertyMappingContainer

namespace ApiStudy.Infrastructure.Services
{
    using System;
    using System.Linq;
    using System.Collections.Generic;

    public class PropertyMappingContainer : IPropertyMappingContainer
    {
        protected internal readonly IList<IPropertyMapping> PropertyMappings = new List<IPropertyMapping>();

        public void Register<T>() where T : IPropertyMapping,new()
        {
            if (PropertyMappings.Any(x => x.GetType() == typeof(T))) return;
            PropertyMappings.Add(new T());
        }

        public IPropertyMapping Resolve<TSource,TDestination>()
        {
            IEnumerable<PropertyMapping<TSource,TDestination>> result = PropertyMappings.OfType<PropertyMapping<TSource,TDestination>>();
            if (result.Count() > 0)
                return result.First();
            throw new InvalidCastException(
               string.Format( "Cannot find property mapping instance for {0},{1}",typeof(TSource),typeof(TDestination)));
        }

        public bool ValidateMappingExistsFor<TSource,TDestination>(string fields)
        {
            if (string.IsNullOrEmpty(fields)) return true;

            IPropertyMapping propertyMapping = Resolve<TSource,TDestination>();

            string[] splitFields = fields.Split(',');

            foreach(string property in splitFields)
            {
                string trimmedProperty = property.Trim();
                int indexOfFirstWhiteSpace = trimmedProperty.IndexOf(' ');
                string propertyName = indexOfFirstWhiteSpace <= 0 ? trimmedProperty : trimmedProperty.Remove(indexOfFirstWhiteSpace);
                
                if (!propertyMapping.MappingDictionary.Keys.Any(x => string.Equals(propertyName,x,StringComparison.OrdinalIgnoreCase))) return false;
            }
            return true;
        }
    }
}

QueryExtensions

namespace ApiStudy.Infrastructure.Extensions
{
    using ApiStudy.Infrastructure.Services;
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Linq.Dynamic.Core;

    public static class QueryExtensions
    {
        public static IQueryable<T> ApplySort<T>(
           this IQueryable<T> data,in string orderBy,in IPropertyMapping propertyMapping)
        {
            if (data == null) throw new ArgumentNullException(nameof(data));
            if (string.IsNullOrEmpty(orderBy)) return data;

            string[] splitOrderBy = orderBy.Split(',');
            foreach(string property in splitOrderBy)
            {
                string trimmedProperty = property.Trim();
                int indexOfFirstSpace = trimmedProperty.IndexOf(' ');
                bool desc = trimmedProperty.EndsWith(" desc");
                string propertyName = indexOfFirstSpace > 0 ? trimmedProperty.Remove(indexOfFirstSpace) : trimmedProperty;
                propertyName = propertyMapping.MappingDictionary.Keys.FirstOrDefault(
                    x => string.Equals(x,propertyName,StringComparison.OrdinalIgnoreCase)); //ignore case of sort property

                if (!propertyMapping.MappingDictionary.TryGetValue(
                    propertyName,out List<MappedProperty> mappedProperties))
                    throw new InvalidCastException($"key mapping for {propertyName} is missing");

                mappedProperties.Reverse();
                foreach(MappedProperty mappedProperty in mappedProperties)
                {
                    if (mappedProperty.Revert) desc = !desc;
                    data = data.OrderBy($"{mappedProperty.Name} {(desc ? "descending" : "ascending")} ");
                }
            }
            return data;
        }
    }
}

UserController 部分代码

[HttpGet(Name = "GetAllApiUsers")]
public async Task<IActionResult> GetAllApiUsers(ApiUserParameters parameters)
{
    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>(parameters.OrderBy))
        return BadRequest("can't find fields for sorting.");

    PaginatedList<ApiUser> apiUsers = await _apiUserRepository.GetAllApiUsersAsync(parameters);

    IEnumerable<ApiUserResource> apiUserResources =
        _mapper.Map<IEnumerable<ApiUser>,IEnumerable<ApiUserResource>>(apiUsers);

    IEnumerable<ApiUserResource> sortedApiUserResources =
        apiUserResources.AsQueryable().ApplySort(
            parameters.OrderBy,_propertyMappingContainer.Resolve<ApiUserResource,ApiUser>());

    var meta = new
    {
        apiUsers.PageIndex,apiUsers.PageSize,apiUsers.PageCount,apiUsers.TotalItemsCount,PreviousPageUrl = apiUsers.HasPreviousPage ? CreateApiUserUrl(parameters,ResourceUriType.PreviousPage) : string.Empty,NextPageUrl = apiUsers.HasNextPage ? CreateApiUserUrl(parameters,ResourceUriType.NextPage) : string.Empty,};
    Response.Headers.Add(
        "X-Pagination",new JsonSerializerSettings
            { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
    return Ok(sortedApiUserResources);
}

private string CreateApiUserUrl(ApiUserParameters parameters,ResourceUriType uriType)
{
    var param = new {
        parameters.PageIndex,parameters.PageSize
    };
    switch (uriType)
    {
        case ResourceUriType.PreviousPage:
            param = new
            {
                PageIndex = parameters.PageIndex - 1,parameters.PageSize
            };
            break;
        case ResourceUriType.NextPage:
            param = new
            {
                PageIndex = parameters.PageIndex + 1,parameters.PageSize
            };
            break;
        case ResourceUriType.CurrentPage:
            break;
        default: break;
    }
    return Url.Link("GetAllApiUsers",param);
}

13. 资源塑形(Resource shaping)

返回资源的指定字段

ApiStudy.Infrastructure.Extensions.TypeExtensions

namespace ApiStudy.Infrastructure.Extensions
{
    using System;
    using System.Collections.Generic;
    using System.Reflection;

    public static class TypeExtensions
    {
        public static IEnumerable<PropertyInfo> GetProeprties(this Type source,string fields = null)
        {
            List<PropertyInfo> propertyInfoList = new List<PropertyInfo>();
            if (string.IsNullOrEmpty(fields))
            {
                propertyInfoList.AddRange(source.GetProperties(BindingFlags.Public | BindingFlags.Instance));
            }
            else
            {
                string[] properties = fields.Trim().Split(',');
                foreach (string propertyName in properties)
                {
                    propertyInfoList.Add(
                        source.GetProperty(
                        propertyName.Trim(),BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase));
                }
            }
            return propertyInfoList;
        }
    }
}

ApiStudy.Infrastructure.Extensions.ObjectExtensions

namespace ApiStudy.Infrastructure.Extensions
{
    using System.Collections.Generic;
    using System.Dynamic;
    using System.Linq;
    using System.Reflection;

    public static class ObjectExtensions
    {
        public static ExpandoObject ToDynamicObject(this object source,in string fields = null)
        {
            List<PropertyInfo> propertyInfoList = source.GetType().GetProeprties(fields).ToList();

            ExpandoObject expandoObject = new ExpandoObject();
            foreach (PropertyInfo propertyInfo in propertyInfoList)
            {
                try
                {
                    (expandoObject as IDictionary<string,object>).Add(
                    propertyInfo.Name,propertyInfo.GetValue(source));
                }
                catch { continue; }
            }
            return expandoObject;
        }

        internal static ExpandoObject ToDynamicObject(this object source,in IEnumerable<PropertyInfo> propertyInfos,in string fields = null)
        {
            ExpandoObject expandoObject = new ExpandoObject();
            foreach (PropertyInfo propertyInfo in propertyInfos)
            {
                try
                {
                    (expandoObject as IDictionary<string,propertyInfo.GetValue(source));
                }
                catch { continue; }
            }
            return expandoObject;
        }
    }
}

ApiStudy.Infrastructure.Extensions.IEnumerableExtensions

namespace ApiStudy.Infrastructure.Extensions
{
    using System;
    using System.Collections.Generic;
    using System.Dynamic;
    using System.Linq;
    using System.Reflection;

    public static class IEnumerableExtensions
    {
        public static IEnumerable<ExpandoObject> ToDynamicObject<T>(
            this IEnumerable<T> source,in string fields = null)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));

            List<ExpandoObject> expandoObejctList = new List<ExpandoObject>();
            List<PropertyInfo> propertyInfoList = typeof(T).GetProeprties(fields).ToList();
            foreach(T x in source)
            {
                expandoObejctList.Add(x.ToDynamicObject(propertyInfoList,fields));
            }
            return expandoObejctList;
        }
    }
}

ApiStudy.Infrastructure.Services.TypeHelperServices

namespace ApiStudy.Infrastructure.Services
{
    using System.Reflection;

    public class TypeHelperServices : ITypeHelperServices
    {
        public bool HasProperties<T>(string fields)
        {
            if (string.IsNullOrEmpty(fields)) return true;

            string[] splitFields = fields.Split(',');
            foreach(string splitField in splitFields)
            {
                string proeprtyName = splitField.Trim();
                PropertyInfo propertyInfo = typeof(T).GetProperty(
                    proeprtyName,BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase);
                if (propertyInfo == null) return false;
            }
            return true;
        }
    }
}

UserContext.GetAllApiUsers(),UserContext.Get()

[HttpGet(Name = "GetAllApiUsers")]
public async Task<IActionResult> GetAllApiUsers(ApiUserParameters parameters)
{
    //added code
    if (!_typeHelper.HasProperties<ApiUserResource>(parameters.Fields))
        return BadRequest("fields not exist.");

    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>());

    //modified code
    IEnumerable<ExpandoObject> sharpedApiUserResources =
        sortedApiUserResources.ToDynamicObject(parameters.Fields);

    var meta = new
    {
        apiUsers.PageIndex,new JsonSerializerSettings
            { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
    //modified code
    return Ok(sharpedApiUserResources);
}

配置返回的json名称风格为CamelCase

StartupDevelopment.ConfigureServices

services.AddMvc(options =>
    {
        options.ReturnHttpNotAcceptable = true;
        options.OutputFormatters.Add(new XmlDataContractSerializerOutputFormatter());
    })
        .AddJsonOptions(options =>
        {
            //added code
            options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
        });

14. HATEOAS

REST里最复杂的约束,构建成熟RESTAPI的核心

可进化性,自我描述
超媒体(Hypermedia,例如超链接)驱动如何消
费和使用API

UserContext

private IEnumerable<LinkResource> CreateLinksForApiUser(string guid,string fields = null)
{
    List<LinkResource> linkResources = new List<LinkResource>();
    if (string.IsNullOrEmpty(fields))
    {
        linkResources.Add(
            new LinkResource(Url.Link("GetApiUser",new { guid }),"self","get"));
    }
    else
    {
        linkResources.Add(
            new LinkResource(Url.Link("GetApiUser",new { guid,fields }),"get"));
    }

    linkResources.Add(
            new LinkResource(Url.Link("DeleteApiUser","Get"));
    return linkResources;
}

private IEnumerable<LinkResource> CreateLinksForApiUsers(ApiUserParameters parameters,bool hasPrevious,bool hasNext)
{
    List<LinkResource> resources = new List<LinkResource>();

    resources.Add(
            new LinkResource(
                CreateApiUserUrl(parameters,ResourceUriType.CurrentPage),"current_page","get"));
    if (hasPrevious)
        resources.Add(
            new LinkResource(
                CreateApiUserUrl(parameters,ResourceUriType.PreviousPage),"previous_page","get"));
    if (hasNext)
        resources.Add(
            new LinkResource(
                CreateApiUserUrl(parameters,"next_page","get"));

    return resources;
}

[HttpGet(Name = "GetAllApiUsers")]
public async Task<IActionResult> GetAllApiUsers(ApiUserParameters parameters)
{
    if (!_typeHelper.HasProperties<ApiUserResource>(parameters.Fields))
        return BadRequest("fields not exist.");

    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>());

    IEnumerable<ExpandoObject> shapedApiUserResources =
        sortedApiUserResources.ToDynamicObject(parameters.Fields);

    IEnumerable<ExpandoObject> shapedApiUserResourcesWithLinks = shapedApiUserResources.Select(
        x =>
        {
            IDictionary<string,object> dict = x as IDictionary<string,object>;
            if(dict.Keys.Contains("guid"))
                dict.Add("links",CreateLinksForApiUser(dict["guid"] as string));
            return dict as ExpandoObject;
        });

    var result = new
    {
        value = shapedApiUserResourcesWithLinks,links = CreateLinksForApiUsers(parameters,apiUsers.HasPreviousPage,apiUsers.HasNextPage)
    };

    var meta = new
    {
        apiUsers.PageIndex,//PreviousPageUrl = apiUsers.HasPreviousPage ? CreateApiUserUrl(parameters,//NextPageUrl = apiUsers.HasNextPage ? CreateApiUserUrl(parameters,new JsonSerializerSettings
            { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
    return Ok(result);
}

14.1. 创建供应商特定媒体类型

application/vnd.mycompany.hateoas+json
- vnd是vendor的缩写，这一条是mime type的原则，表示这个媒体类型是供应商特定的
- 自定义的标识，也可能还包括额外的值，这里我是用的是公司名，随后是hateoas表示返回的响应里面要
  包含链接
- “+json”
在Startup里注册.

14.1.1. 判断Media Type类型

[FromHeader(Name = "Accept")] stringmediaType

//Startup.ConfigureServices 中注册媒体类型
services.AddMvc(options =>
    {
        options.ReturnHttpNotAcceptable = true;
        //options.OutputFormatters.Add(new XmlDataContractSerializerOutputFormatter());
        JsonOutputFormatter formatter = options.OutputFormatters.OfType<JsonOutputFormatter>().FirstOrDefault();
        formatter.SupportedMediaTypes.Add("application/vnd.laggage.hateoas+json");
    })

// get方法中判断媒体类型
if (mediaType == "application/json") 
    return Ok(shapedApiUserResources);
else if (mediaType == "application/vnd.laggage.hateoas+json")
{
    ...
    return;
}

注意,要是的 Action 认识 application/vnd.laggage.hateoss+json,需要在Startup.ConfigureServices中注册这个媒体类型,上面的代码给出了具体操作.

UserContext

[HttpGet(Name = "GetAllApiUsers")]
public async Task<IActionResult> GetAllApiUsers(ApiUserParameters parameters,[FromHeader(Name = "Accept")] string mediaType)
{
    if (!_typeHelper.HasProperties<ApiUserResource>(parameters.Fields))
        return BadRequest("fields not exist.");

    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>());

    IEnumerable<ExpandoObject> shapedApiUserResources =
        sortedApiUserResources.ToDynamicObject(parameters.Fields);

    if (mediaType == "application/json") return Ok(shapedApiUserResources);
    else if (mediaType == "application/vnd.laggage.hateoas+json")
    {
        IEnumerable<ExpandoObject> shapedApiUserResourcesWithLinks = shapedApiUserResources.Select(
            x =>
            {
                IDictionary<string,object>;
                if (dict.Keys.Contains("guid"))
                    dict.Add("links",CreateLinksForApiUser(dict["guid"] as string));
                return dict as ExpandoObject;
            });

        var result = new
        {
            value = shapedApiUserResourcesWithLinks,apiUsers.HasNextPage)
        };

        var meta = new
        {
            apiUsers.PageIndex,};
        Response.Headers.Add(
            "X-Pagination",JsonConvert.SerializeObject(
                meta,new JsonSerializerSettings
                { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
        return Ok(result);
    }
    return NotFound($"Can't find resources for the given media type: [{mediaType}].");
}

[HttpGet("{guid}",Name = "GetApiUser")]
public async Task<IActionResult> Get(string guid,[FromHeader(Name = "Accept")] string mediaType,string fields = null)
{
    if (!_typeHelper.HasProperties<ApiUserResource>(fields))
        return BadRequest("fields not exist.");

    ApiUser apiUser = await _apiUserRepository.GetApiUserByGuidAsync(Guid.Parse(guid));

    if (apiUser is null) return NotFound();
    ApiUserResource apiUserResource = _mapper.Map<ApiUser,ApiUserResource>(apiUser);

    ExpandoObject shapedApiUserResource = apiUserResource.ToDynamicObject(fields);
    if (mediaType == "application/json") return Ok(shapedApiUserResource);

    else if(mediaType == "application/vnd.laggage.hateoas+json")
    {

    
    IDictionary<string,object> shapedApiUserResourceWithLink = shapedApiUserResource as IDictionary<string,object>;
    shapedApiUserResourceWithLink.Add("links",CreateLinksForApiUser(guid,fields));

    return Ok(shapedApiUserResourceWithLink);
    }
    return NotFound(@"Can't find resource for the given media type: [{mediaType}].");
}

自定义Action约束.

RequestHeaderMatchingMediaTypeAttribute

[AttributeUsage(AttributeTargets.All,Inherited = true,AllowMultiple = true)]
public class RequestHeaderMatchingMediaTypeAttribute : Attribute,IActionConstraint
{
    private readonly string _requestHeaderToMatch;
    private readonly string[] _mediaTypes;

    public RequestHeaderMatchingMediaTypeAttribute(string requestHeaderToMatch,string[] mediaTypes)
    {
        _requestHeaderToMatch = requestHeaderToMatch;
        _mediaTypes = mediaTypes;
    }

    public bool Accept(ActionConstraintContext context)
    {
        var requestHeaders = context.RouteContext.HttpContext.Request.Headers;
        if (!requestHeaders.ContainsKey(_requestHeaderToMatch))
        {
            return false;
        }

        foreach (var mediaType in _mediaTypes)
        {
            var mediaTypeMatches = string.Equals(requestHeaders[_requestHeaderToMatch].ToString(),mediaType,StringComparison.OrdinalIgnoreCase);
            if (mediaTypeMatches)
            {
                return true;
            }
        }

        return false;
    }

    public int Order { get; } = 0;
}

UserContext

[HttpGet(Name = "GetAllApiUsers")]
[RequestHeaderMatchingMediaType("Accept",new string[] { "application/vnd.laggage.hateoas+json" })]
public async Task<IActionResult> GetHateoas(ApiUserParameters parameters)
{
    if (!_typeHelper.HasProperties<ApiUserResource>(parameters.Fields))
        return BadRequest("fields not exist.");

    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>());

    IEnumerable<ExpandoObject> shapedApiUserResources =
        sortedApiUserResources.ToDynamicObject(parameters.Fields);

    IEnumerable<ExpandoObject> shapedApiUserResourcesWithLinks = shapedApiUserResources.Select(
            x =>
            {
                IDictionary<string,CreateLinksForApiUser(dict["guid"] as string));
                return dict as ExpandoObject;
            });

    var result = new
    {
        value = shapedApiUserResourcesWithLinks,new JsonSerializerSettings
            { ContractResolver = new CamelCasePropertyNamesContractResolver() }));
    return Ok(result);
}

[HttpGet(Name = "GetAllApiUsers")]
[RequestHeaderMatchingMediaType("Accept",new string[] { "application/json" })]
public async Task<IActionResult> Get(ApiUserParameters parameters)
{
    if (!_typeHelper.HasProperties<ApiUserResource>(parameters.Fields))
        return BadRequest("fields not exist.");

    if (!_propertyMappingContainer.ValidateMappingExistsFor<ApiUserResource,ApiUser>());

    IEnumerable<ExpandoObject> shapedApiUserResources =
        sortedApiUserResources.ToDynamicObject(parameters.Fields);

    return Ok(shapedApiUserResources);
}

[HttpGet("{guid}",Name = "GetApiUser")]
[RequestHeaderMatchingMediaType("Accept",new string[] { "application/vnd.laggage.hateoas+json" })]
public async Task<IActionResult> GetHateoas(string guid,ApiUserResource>(apiUser);

    ExpandoObject shapedApiUserResource = apiUserResource.ToDynamicObject(fields);

    IDictionary<string,fields));

    return Ok(shapedApiUserResourceWithLink);
}

[HttpGet("{guid}",new string[] { "application/json" })]
public async Task<IActionResult> Get(string guid,ApiUserResource>(apiUser);

    ExpandoObject shapedApiUserResource = apiUserResource.ToDynamicObject(fields);

    return Ok(shapedApiUserResource);
}

（编辑：李大同）

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