一文了解.Net Core 3.1 Web API基础知识
一、前言
随着近几年前后端分离、微服务等模式的兴起，.Net Core也似有如火如荼之势 ，自16年发布第一个版本到19年底的3.1 LTS版本，以及将发布的.NET 5，.NET Core一路更迭，在部署和开发工具上也都支持了跨平台应用。一直对.Net Core有所关注，但未涉及太多实际应用，经过一番学习和了解后，于是分享出来。本文主要以.Net Core Web API为例，讲述.Net Core的基本应用及注意事项，对于想通过WebAPI搭建接口应用的开发者，应该能提供一个系统的轮廓和认识，同时和更多的.Net Core开发者交流互动，探本勘误，加强对知识的理解，并帮助更多的人。本文以贴近基本的实际操作为主，部分概念或基础步骤不再赘述，文中如有疏漏，还望不吝斧正。
二、Swagger调试Web API
开发环境：Visual Studio 2019
为解决前后端苦于接口文档与实际不一致、维护和更新文档的耗时费力等问题，swagger应运而生，同时也解决了接口测试问题。话不多说，直接说明应用步骤。
- 新建一个ASP.NET Core Web API应用程序，版本选择.ASP.NET Core 3.1；
- 通过Nuget安装包：Swashbuckle.AspNetCore，当前示例版本5.5.0；
- 在Startup类的ConfigureServices方法内添加以下注入代码：
services.AddSwaggerGen(c => { c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1", Description = "API文档描述", Contact = new OpenApiContact { Email = "5007032@qq.com", Name = "测试项目", //Url = new Uri("") }, License = new OpenApiLicense { Name = "BROOKE许可证", //Url = new Uri("") } }); });Startup类的Configure方法添加如下代码：
//配置Swagger app.UseSwagger(); app.UseSwaggerUI(c => { c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1"); c.RoutePrefix = "api";// 如果设为空，访问路径就是根域名/index.html，设置为空，表示直接在根域名访问；想换一个路径，直接写名字即可，比如直接写c.RoutePrefix = "swagger"; 则访问路径为 根域名/swagger/index.html });Ctrl+F5进入浏览，按上述配置修改路径为 src="https://img2020.cnblogs.com/blog/23487/202009/23487-20200926103609678-1602760898.jpg" alt="" loading="lazy">
然而到这里还没完，相关接口的注释说明我们看不到，通过配置services.AddSwaggerGen(c => { c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1", Description = "API文档描述", Contact = new OpenApiContact { Email = "5007032@qq.com", Name = "测试项目", //Url = new Uri("") }, License = new OpenApiLicense { Name = "BROOKE许可证", //Url = new Uri("") } }); var "{Assembly.GetExecutingAssembly().GetName().Name}."; var Path.Combine(AppContext.BaseDirectory, });上述代码通过反射生成与Web API项目相匹配的然后右键Web API项目、属性、生成，配置
这样，我们以三斜杠（///）方式给类方法属性等相关代码添加注释后，刷新Swagger页面，即可看到注释说明。
如果不想将var basePath = Path.GetDirectoryName(typeof(Program).Assembly.Location);//获取应用程序所在目录var "CoreAPI_Demo.");c.Includetrue);
同时，调整项目生成的
- 隐藏相关接口
对于不想暴漏给Swagger展示的接口，我们可以给相关Controller或Action头加上：[ApiExplorerSettings(IgnoreApi = true)] - 调整系统默认输出路径
项目启动后，默认会访问自带的weatherforecast，如果想调整为其他路径，譬如打开后直接访问Swagger文档，那么调整Properties目录下的launchSettings.json文件，修改launchUrl值为api（前述配置的RoutePrefix值）：{ "$schema": "", "iisSettings": { "windowsAuthentication": false, "anonymousAuthentication": true, "iisExpress": { "applicationUrl": "", "sslPort": 0 } }, "profiles": { "IIS Express": { "commandName": "IISExpress", "launchBrowser": true, "launchUrl": "api", "environmentVariables": { "ASPNETCORE_ENVIRONMENT": "Development" } }, "CoreApi_Demo": { "commandName": "Project", "launchBrowser": true, "launchUrl": "api", "applicationUrl": "", "environmentVariables": { "ASPNETCORE_ENVIRONMENT": "Development" } } }}
三、配置文件
以读取appsettings.json文件为例，当然你也定义其他名称的.json文件进行读取，读取方式一致，该文件类似于Web.config文件。为方便示例，定义appsettings.json文件内容如下：
{ "ConnString": "Data Source=(local);Initial Catalog=Demo;Persist Security Info=True;User ID=DemoUser;Password=123456;MultipleActiveResultSets=True;", "ConnectionStrings": { "MySQLConnection": "server=127.0.0.1;database=mydemo;uid=root;pwd=123456;charset=utf8;SslMode=None;" }, "SystemConfig": { "UploadFile": "/Files", "Domain": "" }, "JwtTokenConfig": { "Secret": "fcbfc8df1ee52ba127ab", "Issuer": "abc.com", "Audience": "Brooke.WebApi", "AccessExpiration": 30, "RefreshExpiration": 60 }, "Logging": { "LogLevel": { "Default": "Information", "Microsoft": "Warning", "Microsoft.Hosting.Lifetime": "Information" } }, "AllowedHosts": "*"}
1、配置文件的基本读取
public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } // This method gets called by the runtime. Use this method to add services to the container. public void ConfigureServices(IServiceCollection services) { services.AddControllers(); //读取方式一 var ConnString = Configuration["ConnString"]; var MySQLConnection = Configuration.GetSection("ConnectionStrings")["MySQLConnection"]; var UploadPath = Configuration.GetSection("SystemConfig")["UploadPath"]; var LogDefault = Configuration.GetSection("Logging").GetSection("LogLevel")["Default"]; //读取方式二 var ConnString2 = Configuration["ConnString"]; var MySQLConnection2 = Configuration["ConnectionStrings:MySQLConnection"]; var UploadPath2 = Configuration["SystemConfig:UploadPath"]; var LogDefault2 = Configuration["Logging:LogLevel:Default"]; } }以上介绍了2种读取配置信息的方式，如果要在Controller内使用，类似地，进行注入并调用如下：
public class ValuesController : ControllerBase { private IConfiguration _configuration; public ValuesController(IConfiguration configuration) { _configuration = configuration; } // GET: api/<ValuesController> [HttpGet] public IEnumerable<string> Get() { var ConnString = _configuration["ConnString"]; var MySQLConnection = _configuration.GetSection("ConnectionStrings")["MySQLConnection"]; var UploadPath = _configuration.GetSection("SystemConfig")["UploadPath"]; var LogDefault = _configuration.GetSection("Logging").GetSection("LogLevel")["Default"]; return new string[] { "value1", "value2" }; } }
2、读取配置文件到自定义对象
以SystemConfig节点为例，定义类如下：
public class SystemConfig { public string UploadPath { get; set; } public string Domain { get; set; } }调整代码如下：
public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } // This method gets called by the runtime. Use this method to add services to the container. public void ConfigureServices(IServiceCollection services) { services.AddControllers(); services.Configure<SystemConfig>(Configuration.GetSection("SystemConfig")); } }然后Controller内进行注入调用：
[Route("api/[controller]/[action]")] [ApiController] public class ValuesController : ControllerBase { private SystemConfig _sysConfig; public ValuesController(IOptions<SystemConfig> sysConfig) { _sysConfig = sysConfig.Value; } [HttpGet] public IEnumerable<string> GetSetting() { var UploadPath = _sysConfig.UploadPath; var Domain = _sysConfig.Domain; return new string[] { "value1", "value2" }; } }3、绑定到静态类方式读取
定义相关静态类如下：
public static class MySettings { public static SystemConfig Setting { get; set; } = new SystemConfig(); }
调整Startup类构造函数如下：
public Startup(IConfiguration configuration, IWebHostEnvironment env) { var builder = new ConfigurationBuilder() .SetBasePath(env.ContentRootPath) .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true); Configuration = builder.Build(); //Configuration = configuration; configuration.GetSection("SystemConfig").Bind(MySettings.Setting);//绑定静态配置类 } 接下来，诸如直接使用：MySettings.Setting.UploadPath 即可调用。
四、文件上传
接口一般少不了文件上传，相比.net framework框架下webapi通过byte数组对象等复杂方式进行文件上传，.Net Core WebApi有了很大变化，其定义了新的IFormFile对象来接收上传文件，直接上Controller代码：
后端代码
[Route("api/[controller]/[action]")] [ApiController] public class UploadController : ControllerBase { private readonly IWebHostEnvironment _env; public UploadController(IWebHostEnvironment env) { _env = env; } public ApiResult UploadFile(List<IFormFile> files) { ApiResult result = new ApiResult();
//注：参数files对象去也可以通过换成： var files = Request.Form.Files;来获取
if (files.Count <= 0) { result.Message = "上传文件不能为空"; return result; } #region 上传 List<string> filenames = new List<string>(); var webRootPath = _env.WebRootPath; var rootFolder = MySettings.Setting.UploadPath; var physicalPath = $"{webRootPath}/{rootFolder}/"; if (!Directory.Exists(physicalPath)) { Directory.CreateDirectory(physicalPath); } foreach (var file in files) { var fileExtension = Path.GetExtension(file.FileName);//获取文件格式，拓展名 var saveName = $"{rootFolder}/{Path.GetRandomFileName()}{fileExtension}"; filenames.Add(saveName);//相对路径 var fileName = webRootPath + saveName; using FileStream fs = System.IO.File.Create(fileName); file.CopyTo(fs); fs.Flush(); }
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