zdam/clojure-clr-webserver.cs

## clojure-clr-webserver.cs
/*
 * This is a litle tech demo to demonstrate using clojureCLR in a CLR web app.
 *
 * A custom IHttpHandler (ClojureHttpHandler) handles invocation of clojure code,
 * and a custom IRouteHandler (ClojureRouteHandler) routes requests to the HttpHandler.
 *
 * See comments in the code for further detail.
 *
 * Cheers, zdam
 * http://zimpler.com/blog/clojureclr-in-an-asp-net-mvc-app
 *
 *      *** Setup instructions are at the bottom of this file ***
 *
 */
using System.IO;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using clojure.lang;
using MvcPlay;

namespace MvcPlay
{
   public class ClojureHttpHandler : IHttpHandler
   {
      private static readonly Symbol CLOJURE_MAIN = Symbol.intern("clojure.main");
      private static readonly Var REQUIRE = RT.var("clojure.core", "require");
      private static readonly Var MAIN = RT.var("clojure.main", "main");

      public void ProcessRequest(HttpContext context)
      {
         var routeValues = RouteData.Values;
         // exit if we weren't told what script to run
         if (routeValues["script"] == null) return;

         // Redirect clojure output to a writer so we can do what we like with it
         TextWriter clojureOutput = new StringWriter();
         RT.OUT.BindRoot(clojureOutput);
         REQUIRE.invoke(CLOJURE_MAIN);

         // Load a script, then execute a particular function inside the script.
         // We can pass parameters in as well.
         // This is just to demo execution of clojureCLR.
         // A real clojureCLR real web app would dispatch to clojure using
         // a more sophisticated mechanism.
         // The approach Enclojure uses could be done here too.
         var scriptToLoad = context.Server.MapPath(@"~\" + routeValues["script"]);
         var functionToExecute = routeValues["function"].ToString();
         var valueOfParam1 = routeValues["param1"].ToString();

         RT.load(scriptToLoad);
         RT.var("zdam", functionToExecute).invoke(valueOfParam1);

         // Ideally you would use clojure itself to generate the html.
         // Port the html builders in enclojure or use a templating system like enlive
         HttpResponse response = context.Response;
         response.Write("<html>");
         response.Write("<body>");
         response.Write("<h1>The result of your funky clojure script:</h1>");
         response.Write("<p>");
         response.Write(clojureOutput.ToString());
         response.Write("</body>");
         response.Write("</html>");
      }

      public bool IsReusable
      {
         get { return false; }
      }

      // Gives us access to the RouteData which we dont have in .Net 3.5
      public RouteData RouteData { get; set; }
   }

   // Route handler to route requests to our ClojureHttpHandler,
   // we also pass the RouteData along.
   public class ClojureRouteHandler : IRouteHandler
   {
      public IHttpHandler GetHttpHandler(RequestContext requestContext)
      {
         return new ClojureHttpHandler { RouteData = requestContext.RouteData };
      }
   }

   public class MvcApplication : System.Web.HttpApplication
   {
      // We wire in the ClojureRouteHandler
      public static void RegisterRoutes(RouteCollection routes)
      {
         routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
         routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });
         // Some simple routes with some defaults
         routes.Add(new Route("{script}/{function}/{param1}",
            new RouteValueDictionary
            { { "script", "first" }, { "function", "default" }, { "param1", 1 } },
            new ClojureRouteHandler()));
         routes.Add(new Route("{*url}", new ClojureRouteHandler()));
      }

      protected void Application_Start()
      {
         AreaRegistration.RegisterAllAreas();
         RegisterRoutes(RouteTable.Routes);
      }
   }
}

/*
 * Setup steps:
 *
 * 1. Ensure you have the ClojureCLR project up and running successfully.
 *    http://github.com/richhickey/clojure-clr#readme
 *
 * 2. From inside the ClojureCLR solution in VS,
 *    - add a new ASP.NET MVC 2 Empty Web Application, called MvcPlay
 *
 * 3. Ensure your project is set up to use IIS, not Cassini,
 *    - ensure your site has Anonymous access allowed.
 *
 * 4. Add project references to:
 *       Clojure
 *       Microsoft.Scripting
 *       Microsoft.Scripting.Core
 *
 * 5. Replace the contents of Global.asax.cs with this file that you are reading.
 *    (If you did not call your project MvcPlay,
 *      you will need to adjust the namespace to match the project name you chose.)
 *
 * 6. In the file yourPathTo\Clojure\Clojure\Lib\RT.cs change line 1974 from this:
 *
 *          yield return Path.GetDirectoryName(Assembly.GetEntryAssembly().Location);
 *
 *          to this:
 *
 *          var foundAssembly = Assembly.GetEntryAssembly();
 *          if (foundAssembly != null)
 *          {
 *             yield return Path.GetDirectoryName(foundAssembly.Location);
 *          }
 *
 * 7. Create a new file in the root of your project,
 *     - called first.clj, copy the following into it:
 *    (ns zdam)
 *    (defn some-math [multiplier]
 *       (pr (* multiplier (+ 1 2 3 4))))
 *
 *    (defn default [&args]
 *       (pr "Welcome to clojure-clr on MVC"))
 *
 * 8. Add a system variable called clojure.load.path,
 *    - point it to yourPathTo\Clojure\Clojure.Main\bin\Debug;
 *
 * 9. Do an IISRESET ! (to ensure the environment variable gets picked up)
 *
 * 10. Run the web project
 *
 * 11. On your browser url, append
 *    first/some-math
 *    first/some-math/8
 *    (eg mine looked like:  http://localhost:5651/first/some-math  )
 *
 *    to invoke the clojure script we created above, with and without parameters.
 *
 */
	/*
	* This is a litle tech demo to demonstrate using clojureCLR in a CLR web app.
	*
	* A custom IHttpHandler (ClojureHttpHandler) handles invocation of clojure code,
	* and a custom IRouteHandler (ClojureRouteHandler) routes requests to the HttpHandler.
	*
	* See comments in the code for further detail.
	*
	* Cheers, zdam
	* http://zimpler.com/blog/clojureclr-in-an-asp-net-mvc-app
	*
	* * Setup instructions are at the bottom of this file *
	*
	*/
	using System.IO;
	using System.Web;
	using System.Web.Mvc;
	using System.Web.Routing;
	using clojure.lang;
	using MvcPlay;

	namespace MvcPlay
	{
	public class ClojureHttpHandler : IHttpHandler
	{
	private static readonly Symbol CLOJURE_MAIN = Symbol.intern("clojure.main");
	private static readonly Var REQUIRE = RT.var("clojure.core", "require");
	private static readonly Var MAIN = RT.var("clojure.main", "main");

	public void ProcessRequest(HttpContext context)
	{
	var routeValues = RouteData.Values;
	// exit if we weren't told what script to run
	if (routeValues["script"] == null) return;

	// Redirect clojure output to a writer so we can do what we like with it
	TextWriter clojureOutput = new StringWriter();
	RT.OUT.BindRoot(clojureOutput);
	REQUIRE.invoke(CLOJURE_MAIN);

	// Load a script, then execute a particular function inside the script.
	// We can pass parameters in as well.
	// This is just to demo execution of clojureCLR.
	// A real clojureCLR real web app would dispatch to clojure using
	// a more sophisticated mechanism.
	// The approach Enclojure uses could be done here too.
	var scriptToLoad = context.Server.MapPath(@"~\" + routeValues["script"]);
	var functionToExecute = routeValues["function"].ToString();
	var valueOfParam1 = routeValues["param1"].ToString();

	RT.load(scriptToLoad);
	RT.var("zdam", functionToExecute).invoke(valueOfParam1);

	// Ideally you would use clojure itself to generate the html.
	// Port the html builders in enclojure or use a templating system like enlive
	HttpResponse response = context.Response;
	response.Write("<html>");
	response.Write("<body>");
	response.Write("<h1>The result of your funky clojure script:</h1>");
	response.Write("<p>");
	response.Write(clojureOutput.ToString());
	response.Write("</body>");
	response.Write("</html>");
	}

	public bool IsReusable
	{
	get { return false; }
	}

	// Gives us access to the RouteData which we dont have in .Net 3.5
	public RouteData RouteData { get; set; }
	}

	// Route handler to route requests to our ClojureHttpHandler,
	// we also pass the RouteData along.
	public class ClojureRouteHandler : IRouteHandler
	{
	public IHttpHandler GetHttpHandler(RequestContext requestContext)
	{
	return new ClojureHttpHandler { RouteData = requestContext.RouteData };
	}
	}

	public class MvcApplication : System.Web.HttpApplication
	{
	// We wire in the ClojureRouteHandler
	public static void RegisterRoutes(RouteCollection routes)
	{
	routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
	routes.IgnoreRoute("{favicon}", new { favicon = @"(./)?favicon.ico(/.*)?" });
	// Some simple routes with some defaults
	routes.Add(new Route("{script}/{function}/{param1}",
	new RouteValueDictionary
	{ { "script", "first" }, { "function", "default" }, { "param1", 1 } },
	new ClojureRouteHandler()));
	routes.Add(new Route("{*url}", new ClojureRouteHandler()));
	}

	protected void Application_Start()
	{
	AreaRegistration.RegisterAllAreas();
	RegisterRoutes(RouteTable.Routes);
	}
	}
	}

	/*
	* Setup steps:
	*
	* 1. Ensure you have the ClojureCLR project up and running successfully.
	* http://github.com/richhickey/clojure-clr#readme
	*
	* 2. From inside the ClojureCLR solution in VS,
	* - add a new ASP.NET MVC 2 Empty Web Application, called MvcPlay
	*
	* 3. Ensure your project is set up to use IIS, not Cassini,
	* - ensure your site has Anonymous access allowed.
	*
	* 4. Add project references to:
	* Clojure
	* Microsoft.Scripting
	* Microsoft.Scripting.Core
	*
	* 5. Replace the contents of Global.asax.cs with this file that you are reading.
	* (If you did not call your project MvcPlay,
	* you will need to adjust the namespace to match the project name you chose.)
	*
	* 6. In the file yourPathTo\Clojure\Clojure\Lib\RT.cs change line 1974 from this:
	*
	* yield return Path.GetDirectoryName(Assembly.GetEntryAssembly().Location);
	*
	* to this:
	*
	* var foundAssembly = Assembly.GetEntryAssembly();
	* if (foundAssembly != null)
	* {
	* yield return Path.GetDirectoryName(foundAssembly.Location);
	* }
	*
	* 7. Create a new file in the root of your project,
	* - called first.clj, copy the following into it:
	* (ns zdam)
	* (defn some-math [multiplier]
	* (pr (* multiplier (+ 1 2 3 4))))
	*
	* (defn default [&args]
	* (pr "Welcome to clojure-clr on MVC"))
	*
	* 8. Add a system variable called clojure.load.path,
	* - point it to yourPathTo\Clojure\Clojure.Main\bin\Debug;
	*
	* 9. Do an IISRESET ! (to ensure the environment variable gets picked up)
	*
	* 10. Run the web project
	*
	* 11. On your browser url, append
	* first/some-math
	* first/some-math/8
	* (eg mine looked like: http://localhost:5651/first/some-math )
	*
	* to invoke the clojure script we created above, with and without parameters.
	*
	*/