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Prerenderer.cs
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Prerenderer.cs
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using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.NodeServices;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;
namespace Microsoft.AspNetCore.SpaServices.Prerendering
{
/// <summary>
/// Performs server-side prerendering by invoking code in Node.js.
/// </summary>
public static class Prerenderer
{
private static readonly object CreateNodeScriptLock = new object();
private static StringAsTempFile NodeScript;
internal static Task<RenderToStringResult> RenderToString(
string applicationBasePath,
INodeServices nodeServices,
CancellationToken applicationStoppingToken,
JavaScriptModuleExport bootModule,
HttpContext httpContext,
object customDataParameter,
int timeoutMilliseconds)
{
// We want to pass the original, unencoded incoming URL data through to Node, so that
// server-side code has the same view of the URL as client-side code (on the client,
// location.pathname returns an unencoded string).
// The following logic handles special characters in URL paths in the same way that
// Node and client-side JS does. For example, the path "/a=b%20c" gets passed through
// unchanged (whereas other .NET APIs do change it - Path.Value will return it as
// "/a=b c" and Path.ToString() will return it as "/a%3db%20c")
var requestFeature = httpContext.Features.Get<IHttpRequestFeature>();
var unencodedPathAndQuery = requestFeature.RawTarget;
var request = httpContext.Request;
var unencodedAbsoluteUrl = $"{request.Scheme}://{request.Host}{unencodedPathAndQuery}";
return RenderToString(
applicationBasePath,
nodeServices,
applicationStoppingToken,
bootModule,
unencodedAbsoluteUrl,
unencodedPathAndQuery,
customDataParameter,
timeoutMilliseconds,
request.PathBase.ToString());
}
/// <summary>
/// Performs server-side prerendering by invoking code in Node.js.
/// </summary>
/// <param name="applicationBasePath">The root path to your application. This is used when resolving project-relative paths.</param>
/// <param name="nodeServices">The instance of <see cref="INodeServices"/> that will be used to invoke JavaScript code.</param>
/// <param name="applicationStoppingToken">A token that indicates when the host application is stopping.</param>
/// <param name="bootModule">The path to the JavaScript file containing the prerendering logic.</param>
/// <param name="requestAbsoluteUrl">The URL of the currently-executing HTTP request. This is supplied to the prerendering code.</param>
/// <param name="requestPathAndQuery">The path and query part of the URL of the currently-executing HTTP request. This is supplied to the prerendering code.</param>
/// <param name="customDataParameter">An optional JSON-serializable parameter to be supplied to the prerendering code.</param>
/// <param name="timeoutMilliseconds">The maximum duration to wait for prerendering to complete.</param>
/// <param name="requestPathBase">The PathBase for the currently-executing HTTP request.</param>
/// <returns></returns>
public static Task<RenderToStringResult> RenderToString(
string applicationBasePath,
INodeServices nodeServices,
CancellationToken applicationStoppingToken,
JavaScriptModuleExport bootModule,
string requestAbsoluteUrl,
string requestPathAndQuery,
object customDataParameter,
int timeoutMilliseconds,
string requestPathBase)
{
return nodeServices.InvokeExportAsync<RenderToStringResult>(
GetNodeScriptFilename(applicationStoppingToken),
"renderToString",
applicationBasePath,
bootModule,
requestAbsoluteUrl,
requestPathAndQuery,
customDataParameter,
timeoutMilliseconds,
requestPathBase);
}
private static string GetNodeScriptFilename(CancellationToken applicationStoppingToken)
{
lock(CreateNodeScriptLock)
{
if (NodeScript == null)
{
var script = EmbeddedResourceReader.Read(typeof(Prerenderer), "/Content/Node/prerenderer.js");
NodeScript = new StringAsTempFile(script, applicationStoppingToken); // Will be cleaned up on process exit
}
}
return NodeScript.FileName;
}
}
}