使用.Net Core编写命令行工具(CLI)的方法

命令行工具(CLI)

命令行工具(CLI)是在图形用户界面得到普及之前使用最为广泛的用户界面，它通常不支持鼠标，用户通过键盘输入指令，计算机接收到指令后，予以执行。

通常认为，命令行工具(CLI)没有图形用户界面(GUI)那么方便用户操作。因为，命令行工具的软件通常需要用户记忆操作的命令，但是，由于其本身的特点，命令行工具要较图形用户界面节约计算机系统的资源。在熟记命令的前提下，使用命令行工具往往要较使用图形用户界面的操作速度要快。所以，图形用户界面的操作系统中，都保留着可选的命令行工具。

另外，命令行工具(CLI)应该是一个开箱即用的工具，不需要安装任何依赖。

一些熟悉的CLI工具如下：

1. dotnet cli

2. vue cli

3.angular cli

4. aws cli

5.azure cli

指令设计

本文将使用.Net Core(版本3.1.102)编写一个CLI工具，实现配置管理以及条目(item)管理(调用WebApi实现)，详情如下：

框架说明

编写CLI使用的主要框架是CommandLineUtils，它主要有以下优势：

1. 良好的语法设计

2. 支持依赖注入

3. 支持generic host

WebApi

提供api让cli调用，实现条目(item)的增删改查：

[Route("api/items")]
[ApiController]
public class ItemsController : ControllerBase
{
  private readonly IMemoryCache _cache;
  private readonly string _key = "items";

  public ItemsController(IMemoryCache memoryCache)
  {
    _cache = memoryCache;
  }

  [HttpGet]
  public IActionResult List()
  {
    var items = _cache.Get<List<Item>>(_key);
    return Ok(items);
  }

  [HttpGet("{id}")]
  public IActionResult Get(string id)
  {
    var item = _cache.Get<List<Item>>(_key).FirstOrDefault(n => n.Id == id);
    return Ok(item);
  }

  [HttpPost]
  public IActionResult Create(ItemForm form)
  {
    var items = _cache.Get<List<Item>>(_key) ?? new List<Item>();

    var item = new Item
    {
      Id = Guid.NewGuid().ToString("N"),
      Name = form.Name,
      Age = form.Age
    };

    items.Add(item);

    _cache.Set(_key, items);
    
    return Ok(item);
  }

  [HttpDelete("{id}")]
  public IActionResult Delete(string id)
  {
    var items = _cache.Get<List<Item>>(_key);

    var item = items?.SingleOrDefault(n => n.Id == id);
    if (item == null)
    {
      return NotFound();
    }

    items.Remove(item);
    _cache.Set(_key, items);

    return Ok();
  }
}

CLI

1. Program - 函数入口

[HelpOption(Inherited = true)] //显示指令帮助，并且让子指令也继承此设置
[Command(Description = "A tool to communicate with web api"), //指令描述
 Subcommand(typeof(ConfigCommand), typeof(ItemCommand))] //子指令
class Program
{
  public static int Main(string[] args)
  {
    //配置依赖注入
    var serviceCollection = new ServiceCollection();

    serviceCollection.AddSingleton(PhysicalConsole.Singleton);
    serviceCollection.AddSingleton<IConfigService, ConfigService>();
    serviceCollection.AddHttpClient<IItemClient, ItemClient>();

    var services = serviceCollection.BuildServiceProvider();

    var app = new CommandLineApplication<Program>();
    app.Conventions
      .UseDefaultConventions()
      .UseConstructorInjection(services);

    var console = (IConsole)services.GetService(typeof(IConsole));

    try
    {
      return app.Execute(args);
    }
    catch (UnrecognizedCommandParsingException ex) //处理未定义指令
    {
      console.WriteLine(ex.Message);
      return -1;
    }
  }

  //指令逻辑
  private int OnExecute(CommandLineApplication app, IConsole console)
  {
    console.WriteLine("Please specify a command.");
    app.ShowHelp();
    return 1;
  }
}

2. ConfigCommand和ItemCommand - 实现的功能比较简单，主要是指令描述以及指定对应的子指令

[Command("config", Description = "Manage config"),
 Subcommand(typeof(GetCommand), typeof(SetCommand))]
public class ConfigCommand
{
  private int OnExecute(CommandLineApplication app, IConsole console)
  {
    console.Error.WriteLine("Please submit a sub command.");
    app.ShowHelp();
    return 1;
  }
}

[Command("item", Description = "Manage item"),
 Subcommand(typeof(CreateCommand), typeof(GetCommand), typeof(ListCommand), typeof(DeleteCommand))]
public class ItemCommand
{
  private int OnExecute(CommandLineApplication app, IConsole console)
  {
    console.Error.WriteLine("Please submit a sub command.");
    app.ShowHelp();
    return 1;
  }
}

3.ConfigService - 配置管理的具体实现，主要是文件读写

public interface IConfigService
{
  void Set();

  Config Get();
}

public class ConfigService: IConfigService
{
  private readonly IConsole _console;
  private readonly string _directoryName;
  private readonly string _fileName;

  public ConfigService(IConsole console)
  {
    _console = console;
    _directoryName = ".api-cli";
    _fileName = "config.json";
  }

  public void Set()
  {
    var directory = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), _directoryName);
    if (!Directory.Exists(directory))
    {
      Directory.CreateDirectory(directory);
    }

    var config = new Config
    {
      //弹出交互框，让用户输入，设置默认值为http://localhost:5000/
      Endpoint = Prompt.GetString("Specify the endpoint:", "http://localhost:5000/")
    };

    if (!config.Endpoint.EndsWith("/"))
    {
      config.Endpoint += "/";
    }

    var filePath = Path.Combine(directory, _fileName);

    using (var outputFile = new StreamWriter(filePath, false, Encoding.UTF8))
    {
      outputFile.WriteLine(JsonConvert.SerializeObject(config, Formatting.Indented));
    }
    _console.WriteLine($"Config saved in {filePath}.");
  }

  public Config Get()
  {
    var filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), _directoryName, _fileName);

    if (File.Exists(filePath))
    {
      var content = File.ReadAllText(filePath);
      try
      {
        var config = JsonConvert.DeserializeObject<Config>(content);
        return config;
      }
      catch
      {
        _console.WriteLine("The config is invalid, please use 'config set' command to reset one.");
      }
    }
    else
    {
      _console.WriteLine("Config is not existed, please use 'config set' command to set one.");
    }

    return null;
  }
}

4.ItemClient - 调用Web Api的具体实现，使用HttpClientFactory的方式

public interface IItemClient
{
  Task<string> Create(ItemForm form);

  Task<string> Get(string id);

  Task<string> List();

  Task<string> Delete(string id);
}

public class ItemClient : IItemClient
{
  public HttpClient Client { get; }

  public ItemClient(HttpClient client, IConfigService configService)
  {
    var config = configService.Get();
    if (config == null)
    {
      return;
    }

    client.BaseAddress = new Uri(config.Endpoint);

    Client = client;
  }

  public async Task<string> Create(ItemForm form)
  {
    var content = new StringContent(JsonConvert.SerializeObject(form), Encoding.UTF8, "application/json");
    var result = await Client.PostAsync("/api/items", content);

    if (result.IsSuccessStatusCode)
    {
      var stream = await result.Content.ReadAsStreamAsync();
      var item = Deserialize<Item>(stream);
      return $"Item created, info:{item}";
    }

    return "Error occur, please again later.";
  }

  public async Task<string> Get(string id)
  {
    var result = await Client.GetAsync($"/api/items/{id}");

    if (result.IsSuccessStatusCode)
    {
      var stream = await result.Content.ReadAsStreamAsync();
      var item = Deserialize<Item>(stream);

      var response = new StringBuilder();
      response.AppendLine($"{"Id".PadRight(40, ' ')}{"Name".PadRight(20, ' ')}Age");
      response.AppendLine($"{item.Id.PadRight(40, ' ')}{item.Name.PadRight(20, ' ')}{item.Age}");
      return response.ToString();
    }

    return "Error occur, please again later.";
  }

  public async Task<string> List()
  {
    var result = await Client.GetAsync($"/api/items");

    if (result.IsSuccessStatusCode)
    {
      var stream = await result.Content.ReadAsStreamAsync();
      var items = Deserialize<List<Item>>(stream);

      var response = new StringBuilder();
      response.AppendLine($"{"Id".PadRight(40, ' ')}{"Name".PadRight(20, ' ')}Age");

      if (items != null && items.Count > 0)
      {
        foreach (var item in items)
        {
          response.AppendLine($"{item.Id.PadRight(40, ' ')}{item.Name.PadRight(20, ' ')}{item.Age}");
        }
      }
      
      return response.ToString();
    }

    return "Error occur, please again later.";
  }

  public async Task<string> Delete(string id)
  {
    var result = await Client.DeleteAsync($"/api/items/{id}");

    if (result.IsSuccessStatusCode)
    {
      return $"Item {id} deleted.";
    }

    if (result.StatusCode == HttpStatusCode.NotFound)
    {
      return $"Item {id} not found.";
    }

    return "Error occur, please again later.";
  }

  private static T Deserialize<T>(Stream stream)
  {
    using var reader = new JsonTextReader(new StreamReader(stream));
    var serializer = new JsonSerializer();
    return (T)serializer.Deserialize(reader, typeof(T));
  }
}

如何发布

在项目文件中设置发布程序的名称(AssemblyName)：

　<PropertyGroup>
　　 <OutputType>Exe</OutputType>
　　 <TargetFramework>netcoreapp3.1</TargetFramework>
　　 <AssemblyName>api-cli</AssemblyName>
　　</PropertyGroup>

进入控制台程序目录：

cd src/NetCoreCLI

发布Linux使用版本：

　dotnet publish -c Release -r linux-x64 /p:PublishSingleFile=true

发布Windows使用版本：

dotnet publish -c Release -r win-x64 /p:PublishSingleFile=true

发布MAC使用版本：

dotnet publish -c Release -r osx-x64 /p:PublishSingleFile=true

使用示例

这里使用Linux作为示例环境。

1. 以docker的方式启动web api

2. 虚拟机上没有安装.net core的环境

3. 把编译好的CLI工具拷贝到虚拟机上，授权并移动到PATH中（如果不移动，可以通过./api-cli的方式调用）

sudo chmod +x api-cli #授权
sudo mv ./api-cli /usr/local/bin/api-cli #移动到PATH

4. 设置配置文件：api-cli config set

5. 查看配置文件：api-cli config get

6. 创建条目：api-cli item create

7. 条目列表：api-cli item list

8. 获取条目：api-cli item get

9. 删除条目：api-cli item delete

10. 指令帮助：api-cli -h， api-cli config -h， api-cli item -h

11. 错误指令：api-cli xxx

源码地址

https://github.com/ErikXu/NetCoreCLI

参考资料

https://docs.microsoft.com/en-us/dotnet/core/rid-catalog

https://medium.com/swlh/build-a-command-line-interface-cli-program-with-net-core-428c4c85221