.Net工作流elsa-workflows官方文档学习：简单的文件审批工作流
网页：https://elsa-workflows.github.io/elsa-core/docs/guides-document-approval
在本节中，我们将执行以下操作：
- 以编程方式定义长时间运行的工作流，在HTTP请求到达指定URL时执行，接受带有JSON负载的POST请求，该JSON负载表示要检查的文档。
- 相关活动组件：ReceiveHttpRequest，WriteHttpResponse，Fork，Join，SetVariable，Signaled，SendEmail和IfElse。
此工作流的目的是允许作者提交文档（建模为JSON对象），并允许审阅者批准或拒绝此文档。 此外，如果审阅者花费的时间太长而无法采取行动，则会定期提醒他。
我们将发布到工作流中的JSON有效负载如下所示：
{
"Id": "1",
"Author": {
"Name": "John",
"Email": "john@gmail.com"
},
"Body": "This is sample document."
}
使用访问此模型的JavaScript表达式查看活动时，请牢记此结构。
创建ASP.NET Core项目
创建一个名为Elsa.Guides.ContentApproval.WebApp的新的空ASP.NET Core项目，并添加以下程序包：
- Elsa.Core
- Elsa.Activities.Email
- Elsa.Activities.Http
- Elsa.Activities.Timers
创建工作流类
using System; using System.Dynamic; using System.Net; using System.Net.Http; using Elsa.Activities.ControlFlow; using Elsa.Activities.Email.Activities; using Elsa.Activities.Http.Activities; using Elsa.Activities.Primitives; using Elsa.Activities.Timers.Activities; using Elsa.Activities.Workflows; using Elsa.Expressions; using Elsa.Services; using Elsa.Services.Models; namespace Elsa.Guides.DocumentApproval.WebApp { public class DocumentApprovalWorkflow : IWorkflow { public void Build(IWorkflowBuilder builder) { builder .StartWith<ReceiveHttpRequest>( x => { x.Method = HttpMethod.Post.Method; x.Path = new Uri("/documents", UriKind.Relative); x.ReadContent = true; } ) .Then<SetVariable>( x => { x.VariableName = "Document"; x.ValueExpression = new JavaScriptExpression<ExpandoObject>("lastResult().Body"); } ) .Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document received from ${Document.Author.Name}`"); x.Body = new JavaScriptExpression<string>( "`Document from ${Document.Author.Name} received for review. " + "<a href=\"${signalUrl('Approve')}\">Approve</a> or <a href=\"${signalUrl('Reject')}\">Reject</a>`" ); } ) .Then<WriteHttpResponse>( x => { x.Content = new LiteralExpression( "<h1>Request for Approval Sent</h1><p>Your document has been received and will be reviewed shortly.</p>" ); x.ContentType = "text/html"; x.StatusCode = HttpStatusCode.OK; x.ResponseHeaders = new LiteralExpression("X-Powered-By=Elsa Workflows"); } ) .Then<SetVariable>( x => { x.VariableName = "Approved"; x.ValueExpression = new JavaScriptExpression<bool>("false"); } ) .Then<Fork>( x => { x.Branches = new[] { "Approve", "Reject", "Remind" }; }, fork => { fork .When("Approve") .Then<Signaled>(x => x.Signal = new LiteralExpression("Approve")) .Then("Join"); fork .When("Reject") .Then<Signaled>(x => x.Signal = new LiteralExpression("Reject")) .Then("Join"); fork .When("Remind") .Then<TimerEvent>( x => x.TimeoutExpression = new LiteralExpression<TimeSpan>("00:00:10"), name: "RemindTimer" ) .Then<IfElse>( x => x.ConditionExpression = new JavaScriptExpression<bool>("!!Approved"), ifElse => { ifElse .When(OutcomeNames.False) .Then<SendEmail>( x => { x.From = new LiteralExpression("reminder@acme.com"); x.To = new LiteralExpression("approval@acme.com"); x.Subject = new JavaScriptExpression<string>( "`${Document.Author.Name} is awaiting for your review!`" ); x.Body = new JavaScriptExpression<string>( "`Don't forget to review document ${Document.Id}.<br/>" + "<a href=\"${signalUrl('Approve')}\">Approve</a> or <a href=\"${signalUrl('Reject')}\">Reject</a>`" ); } ) .Then("RemindTimer"); } ); } ) .Then<Join>(x => x.Mode = Join.JoinMode.WaitAny, name: "Join") .Then<SetVariable>( x => { x.VariableName = "Approved"; x.ValueExpression = new JavaScriptExpression<object>("input('Signal') === 'Approve'"); } ) .Then<IfElse>( x => x.ConditionExpression = new JavaScriptExpression<bool>("!!Approved"), ifElse => { ifElse .When(OutcomeNames.True) .Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document ${Document.Id} approved!`"); x.Body = new JavaScriptExpression<string>( "`Great job ${Document.Author.Name}, that document is perfect! Keep it up.`" ); } ); ifElse .When(OutcomeNames.False) .Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document ${Document.Id} rejected`"); x.Body = new JavaScriptExpression<string>( "`Sorry ${Document.Author.Name}, that document isn't good enough. Please try again.`" ); } ); } ); } } }
ReceiveHttpRequest
.StartWith<ReceiveHttpRequest>( x => { x.Method = HttpMethod.Post.Method; x.Path = new Uri("/documents", UriKind.Relative); x.ReadContent = true; } )
我们将其 ReadContent 设置为 true，以便读取和解析请求主体。解析内容是通过适当的 IContentFormatter 完成的，该 IContentFormatter 是根据请求体的内容类型选择的。目前，只支持 application/json 和 text/json 内容类型，但也将添加对 application/x-www-form-urlencoded 和 multipart/form-data 的支持。它将把 JSON 内容解析为 ExpandoObject。
SetVariable
.Then<SetVariable>( x => { x.VariableName = "Document"; x.ValueExpression = new JavaScriptExpression<ExpandoObject>("lastResult().Body"); } )
该表达式的工作方式如下：
- 首先，我们调用一个名为 lastResult 的函数。此函数返回工作流执行上下文的 LastResult 值。因为这是由 ReceiveHttpRequest 设置的，所以它将包含一个对象，该对象保存有关接收到的 HTTP 请求的详细信息，包括一个 Body 属性，该属性包含已解析的 JSON 对象。
正如我们将在下一个活动中看到的，我们使用 SetVariable 活动来简化从其他活动访问它的过程。
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SendEmail
.Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document received from ${Document.Author.Name}`"); x.Body = new JavaScriptExpression<string>( "`Document from ${Document.Author.Name} received for review. " + "<a href=\"${signalUrl('Approve')}\">Approve</a> or <a href=\"${signalUrl('Reject')}\">Reject</a>`" ); } )
我们要做的第二件事是通知审阅者新的文件已提交。 为此，我们使用SendEmail活动发送电子邮件。 我们使用LiteralExpression和JavaScriptExpression对象的混合配置此活动。 LiteralExpression返回传递给其构造函数的文字字符串值，如果使用泛型类型重载，则可以选择将其转换为给定类型。 在这种情况下，我们只需要指定一个文字电子邮件地址：“ approval@acme.com。
To，Subject和Body的表达式更有趣，因为它们演示了如何使用JavaScript表达式访问我们之前定义的Document变量。
Body属性表达式使用一个名为signalUrl的JavaScript函数，该函数接受一个表示信号名称的参数。 这样做是生成一个包含安全令牌的绝对URL，该令牌包含以下信息：
- 工作流实例ID
- 信号名称
当对生成的URL发出HTTP请求时（例如，在收到电子邮件时单击该请求），Elsa将识别该URL并触发与安全令牌携带的工作流实例ID相匹配的工作流实例。 更具体地说，将通过信号事件触发工作流程，如果该事件被该类型的活动阻止，则导致工作流程恢复。 我们将在短期内通知您。
首先，我们要向客户端发送HTTP响应，并说文档已成功接收。
WriteHttpResponse
.Then<WriteHttpResponse>( x => { x.Content = new LiteralExpression( "<h1>Request for Approval Sent</h1><p>Your document has been received and will be reviewed shortly.</p>" ); x.ContentType = "text/html"; x.StatusCode = HttpStatusCode.OK; x.ResponseHeaders = new LiteralExpression("X-Powered-By=Elsa Workflows"); } )
WriteHttpResponse活动只是将响应写回到客户端。 通过该活动，我们可以配置状态码，内容类型，内容主体和响应头以发送回去。
SetVariable
.Then<SetVariable>( x => { x.VariableName = "Approved"; x.ValueExpression = new LiteralExpression<bool>("false"); } )
这次，我们使用SetVariable活动来初始化另一个名为Approved的变量。 稍后将使用此变量来检查审阅者是否单击了“批准”或“拒绝”链接（触发了适当的信号）。 我们需要预先初始化此变量，因为在下一个活动中，我们会将执行分叉到3个分支中，其中一个会启动一个定期检查此变量的计时器。 如果未定义变量，则工作流程将出错。
Fork, IfElse
.Then<Fork>( x => { x.Branches = new[] { "Approve", "Reject", "Remind" }; }, fork => { fork .When("Approve") .Then<Signaled>(x => x.Signal = new LiteralExpression("Approve")) .Then("Join"); fork .When("Reject") .Then<Signaled>(x => x.Signal = new LiteralExpression("Reject")) .Then("Join"); fork .When("Remind") .Then<TimerEvent>( x => x.TimeoutExpression = new LiteralExpression<TimeSpan>("00:00:10"), name: "RemindTimer" ) .Then<IfElse>( ... ); } )
Fork活动使我们可以将工作流执行分为多个分支。 在这种情况下，我们将分支到以下分支：
- Approve
- Reject
- Remind
对于Approve和Reject分支，我们都连接到前面提到的Signaled活动。 因为我们分叉执行，所以这两个活动的工作流程都将被阻塞。 当审阅者单击电子邮件中的任一链接时，将触发这些活动之一并恢复工作流程的执行。 发生这种情况时，工作流程将继续执行“加入”活动，稍后将进行介绍。
连接活动
工作流不仅会在两个有信号的活动上被阻止，而且还会在 TimerEvent 活动上被阻止。此活动被配置为每10秒触发一次。每隔10秒，工作流的这个分支将继续执行 IfElse 活动。注意，我们为 TimerEvent 活动指定了一个 ID 值: “ RemindTimer”。指定显式 ID 允许我们引用工作流其他部分的活动。
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IfElse
.Then<IfElse>( x => x.ConditionExpression = new JavaScriptExpression<bool>("!!Approved"), ifElse => { ifElse .When(OutcomeNames.False) .Then<SendEmail>( x => { x.From = new LiteralExpression("reminder@acme.com"); x.To = new LiteralExpression("approval@acme.com"); x.Subject = new JavaScriptExpression<string>( "`${Document.Author.Name} is awaiting for your review!`" ); x.Body = new JavaScriptExpression<string>( "`Don't forget to review document ${Document.Id}.<br/>" + "<a href=\"${signalUrl('Approve')}\">Approve</a> or <a href=\"${signalUrl('Reject')}\">Reject</a>`" ); } ) .Then("RemindTimer"); } );
如果为 false，则使用 SendEmail 活动发送电子邮件(我们以前见过) ，并使用 Then (“ Reminder”)循环回到 TimerEvent。现在您了解了为什么我们为 TimerEvent 提供一个 ID 值。
Join
.Then<Join>(x => x.Mode = Join.JoinMode.WaitAny, name: "Join") .Then<SetVariable>( x => { x.VariableName = "Approved"; x.ValueExpression = new JavaScriptExpression<object>("input('Signal') === 'Approve'"); } )
IfElse
.Then<IfElse>( x => x.ConditionExpression = new JavaScriptExpression<bool>("!!Approved"), ifElse => { ifElse .When(OutcomeNames.True) .Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document ${Document.Id} approved!`"); x.Body = new JavaScriptExpression<string>( "`Great job ${Document.Author.Name}, that document is perfect! Keep it up.`" ); } ); ifElse .When(OutcomeNames.False) .Then<SendEmail>( x => { x.From = new LiteralExpression("approval@acme.com"); x.To = new JavaScriptExpression<string>("Document.Author.Email"); x.Subject = new JavaScriptExpression<string>("`Document ${Document.Id} rejected`"); x.Body = new JavaScriptExpression<string>( "`Sorry ${Document.Author.Name}, that document isn't good enough. Please try again.`" ); } ); } );
更新Startup文件
using Elsa.Activities.Email.Extensions; using Elsa.Activities.Http.Extensions; using Elsa.Activities.Timers.Extensions; using Elsa.Extensions; using Elsa.Services; using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; namespace Elsa.Guides.DocumentApproval.WebApp { public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services .AddElsa() .AddHttpActivities(options => options.Bind(Configuration.GetSection("Http"))) .AddEmailActivities(options => options.Bind(Configuration.GetSection("Smtp"))) .AddTimerActivities(options => options.Bind(Configuration.GetSection("BackgroundRunner"))) .AddWorkflow<DocumentApprovalWorkflow>; } public void Configure(IApplicationBuilder app) { app.UseHttpActivities(); } } }
更新Appsettings.json
{
"Logging": {
"LogLevel": {
"Default": "Warning"
}
},
"AllowedHosts": "*",
"Http": {
"BaseUrl": "http://localhost:5000"
},
"Smtp": {
"Host": "localhost",
"Port": "2525"
},
"BackgroundRunner": {
"SweepInterval": "PT01S"
}
}
运行
Docker Compose和.HTTP文件：或者，您可以选择使用随附的docker-compose文件从docker容器中运行Smtp4Dev服务，然后使用http-request.http文件触发HTTP请求。 这需要在您的计算机上安装Docker Desktop。
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首先，启动应用程序。 如果一切顺利，则Web主机将准备在http：// localhost：5000处接收传入的HTTP请求：
控制台窗口显示：
Hosting environment: Production Content root path: C:\Projects\Elsa\elsa-guides\src\Elsa.Guides.DocumentApproval.WebApp Now listening on: http://localhost:5000 Now listening on: https://localhost:5001 Application started. Press Ctrl+C to shut down.
POST /documents HTTP/1.1
Host: localhost:5000
Content-Type: application/json
{
"Id": "3",
"Author": {
"Name": "John",
"Email": "john@gmail.com"
},
"Body": "This is sample document."
}
curl --location --request POST "http://localhost:5000/documents" \
--header "Content-Type: application/json" \
--data "{
\"Id\": \"3\",
\"Author\": {
\"Name\": \"John\",
\"Email\": \"john@gmail.com\"
},
\"Body\": \"This is sample document.\"
}"
<h1>Request for Approval Sent</h1> <p>Your document has been received and will be reviewed shortly.</p>
每隔10秒左右，提醒电子邮件信息就应该出现:
这将一直继续，直到您单击“批准”或“拒绝”链接为止。
总结
源码
