一个适合于.NET Core的超轻量级工作流引擎：Workflow-Core
最近想做一个OA相关的网站开发，一直都听说有workflow的东西，之前也断断续续学习过 Workflow Foundation 4.0，还是没有搞明白到底能够用它做什么
但还是觉得workflow在某种情形下应该可以适用，虽然还没有答案，网上搜楼了一通，发现一个workflow-core的东西，觉得挺有意思，遂停下来，琢磨一下，现分享与大家。
* 简介
workflow core的GitHub主页
https://github.com/danielgerlag/workflow-core
如主页上介绍的，workflow core作为一个轻量级workflow引擎，可以嵌入到项目中，其底层是用.NET standard 2.0开发，可以用来追踪长时间运行的任务状态，功能也比较强大，支持插件形式持久化，和多节点并行处理，貌似很牛。并且目前有给一个 Conductor 项目，就是使用workflow core作为内核的workflow服务器（原来运行workflow，需要单独的一个服务器啊），Conductor这里就不展开了。workflow core支持fluent语法，写起来也非常美观，虽然没有WF那样有图形化的操作界面，但感觉代码比较干净。
* 示例1
新建一个项目，指明使用.net framework 4.6.1以上，新建项目后，在Package Manager Console中，安装workflow core：Install-Package WorkflowCore，安装这个包会默认安装一系列的依赖包
可能由于版本的关系，还需要另外安装两个包：Microsoft.Extensions.Logging 和 Microsoft.Extensions.Logging.Debug。这样就可以按照Sample 01开始编写代码了
Sample01是一个helloworld，包含了几部分内容：
1. 构建StepBody，就是workflow中需要执行的内容，每个类继承自StepBody这个虚拟类，重载ExecutionResult Run(IStepExecutionContext context)，这个函数中完成所需的工作
public class HelloWorld : StepBody { private ILogger logger; public HelloWorld(ILoggerFactory loggerFactory) { logger = loggerFactory.CreateLogger<HelloWorld>(); } public override ExecutionResult Run(IStepExecutionContext context) { Console.WriteLine("Hello world, workflow"); logger.LogInformation("Helloworld workflow"); return ExecutionResult.Next(); } } public class GoodbyeWorld : StepBody { private ILogger logger; public GoodbyeWorld(ILoggerFactory loggerFactory) { logger = loggerFactory.CreateLogger<GoodbyeWorld>(); } public override ExecutionResult Run(IStepExecutionContext context) { Console.WriteLine("Workflow, Goodbye"); logger.LogInformation("Goodbye workflow"); return ExecutionResult.Next(); } } public class SleepStep : StepBody { private ILogger logger; public SleepStep(ILoggerFactory loggerFactory) { logger = loggerFactory.CreateLogger("SleepStep"); } public override ExecutionResult Run(IStepExecutionContext context) { Thread.Sleep(1000); logger.LogInformation("Sleeped"); return ExecutionResult.Next(); } }
2. 构建workflow，实现IWorkflow接口，每个workflow有一个Id和一个Version，标明这个workflow的身份，这里通过两种方法构建了HelloWorkflow
public class HelloWorkflow : IWorkflow { public string Id => "HelloWorkflow"; public int Version => 1; public void Build(IWorkflowBuilder<object> builder) { builder.StartWith(context => { Console.WriteLine("Hello world"); return ExecutionResult.Next(); }) .Then(context => { Thread.Sleep(500); Console.WriteLine("sleeped"); return ExecutionResult.Next(); }) .Then(context => { Console.WriteLine("Goodbye world"); return ExecutionResult.Next(); }); } } public class HelloWorkflow2 : IWorkflow { public string Id => "HelloWorkflow"; public int Version => 2; public void Build(IWorkflowBuilder<object> builder) { builder.StartWith<HelloWorld>() .Then<SleepStep>() .Then<GoodbyeWorld>(); } }
3. 万事俱备，准备让workflow运行起来。第一步当然是需要搭建service，Workflow Core通过Injection命名空间的ServiceCollection添加了Workflow相关的服务，对于有参数的StepBody，需要先通过service的AddTransient函数注册，这样才能正确的构造对象
/// <summary> /// 配置workflow /// </summary> /// <returns></returns> private IServiceProvider ConfigureServices() { //setup dependency injection IServiceCollection services = new ServiceCollection(); services.AddLogging(); services.AddWorkflow(); //services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow")); // 这些个构造函数带参数的，需要添加到transient中 services.AddTransient<HelloWorld>(); services.AddTransient<GoodbyeWorld>(); services.AddTransient<SleepStep>(); var serviceProvider = services.BuildServiceProvider(); //config logging var loggerFactory = serviceProvider.GetService<ILoggerFactory>(); loggerFactory.AddProvider(new DebugLoggerProvider()); return serviceProvider; }
接下来，启动workflow 主机，并启动一次workflow，将整个窗体代码贴一下，这样比较清晰
using Microsoft.Extensions.DependencyInjection;using Microsoft.Extensions.Logging;using Microsoft.Extensions.Logging.Console;using Microsoft.Extensions.Logging.Debug;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;using WorkflowCore.Interface;using WorkflowCore.Services;using WorkFlowCoreTest.MyWorkflow;namespace WorkFlowCoreTest{ /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { IServiceProvider serviceProvider = null; bool serviceStarted = false; public MainWindow() { InitializeComponent(); } private void StartWorkflow() { if (serviceProvider == null) { serviceProvider = ConfigureServices(); var host1 = serviceProvider.GetService<IWorkflowHost>(); host1.RegisterWorkflow<HelloWorkflow>(); host1.RegisterWorkflow<HelloWorkflow2>(); } var host = serviceProvider.GetService<IWorkflowHost>(); var wd = host.Registry.GetDefinition("HelloWorkflow"); // 如果host启动了，不能再次启动，但没有判断方法 if (!serviceStarted) { host.Start(); serviceStarted = true; } // 启动workflow工作流 host.StartWorkflow("HelloWorkflow", 1, data: null); // //host.StartWorkflow("HelloWorkflow");//, 2, data: null, 默认会启用版本高的 } private void StopWorkflow() { var host = serviceProvider.GetService<IWorkflowHost>(); host.Stop(); serviceStarted = false; } /// <summary> /// 配置workflow /// </summary> /// <returns></returns> private IServiceProvider ConfigureServices() { //setup dependency injection IServiceCollection services = new ServiceCollection(); services.AddLogging(); services.AddWorkflow(); //services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow")); // 这些个构造函数带参数的，需要添加到transient中 services.AddTransient<HelloWorld>(); services.AddTransient<GoodbyeWorld>(); services.AddTransient<SleepStep>(); var serviceProvider = services.BuildServiceProvider(); //config logging var loggerFactory = serviceProvider.GetService<ILoggerFactory>(); loggerFactory.AddProvider(new DebugLoggerProvider()); return serviceProvider; } private void startButton_Click(object sender, RoutedEventArgs e) { StartWorkflow(); } private void stopButton_Click(object sender, RoutedEventArgs e) { StopWorkflow(); } }}
就这样一个简单的Workflow Core例子就完成了，总体来说，还是很简单，清晰的。
出处：
https://www.cnblogs.com/keep-study-to-die/p/12001408.html
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