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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