URL Aliases and Redirects

Introduction

With HTTP handlers, it is possible to express URL transformations such as aliases and redirects.

Alias

An alias is a GET handle that returns the result of an Self.GET call.

For web apps, the URL displayed in the browser address bar does not get changed to the destination value.

Example:

Handle.GET("/pmail", () =>
{
  return Self.GET("/pmail/inbox");
});

Starcounter gateway has support for aliases which is described in Network Gateway section.

Redirect

An HTTP redirect is a server response that guides the client to access the resource using a different URL. It is achieved by an appropriate HTTP status code and value of the Location header.

For web apps, the URL displayed in the browser address bar gets changed to the destination value.

Example:

Handle.GET("/villains/anakin-skywalker", () =>
{
  var resp = new Response()
  {
    StatusCode = 302,
    StatusDescription = "Moved Permanently"
  };
  resp.Headers["Location"] = "/villains/darth-vader";
  return resp;
});

API for Redirection

To redirect your app's URL handler to another handler, call GET /sc/redirect/{PortNumber}{FromUri};{ToUri} on system port (by default 8181).

For example, to create redirection of / to /myapp on port 8080, the following handler should be called: GET /sc/redirect/8080/;/myapp on system port (by default 8181).

To create redirection on the startup of your application, you may call Http.GET(8181, "/sc/redirect/8080/;/myapp");. Keep in mind, that any other app can overwrite this redirect because there can only be one app handling the host root.

Uri Aliasing

URI Aliasing in Network Gateway

The classical example is to alias root URI to some other URI in your application. URI aliases are configured in scnetworkgateway.xml in your server directory. The following section is an excerpt from gateway configuration:

<UriAliases>
    <UriAlias>
        <HttpMethod>GET</HttpMethod>
        <FromUri>/</FromUri>
        <ToUri>/index.html</ToUri>
        <Port>8181</Port>
    </UriAlias>

    <UriAlias>
        <HttpMethod>GET</HttpMethod>
        <FromUri>/</FromUri>
        <ToUri>/launcher</ToUri>
        <Port>8080</Port>
    </UriAlias>
</UriAliases>

• HttpMethod: for which HTTP method the alias is created.

• FromUri: URI that should be aliased.

• ToUri: URI to which the aliased URI should be changed.

• Port: port on which this rule should apply.

In the example above we have declared two URI aliases: 1. On port 8181 from URI "/" to "/index.html". This is often used to display application initial "index" page when user just specifies the DNS name of the Web-server in the browser. 2. On port 8080 from URI "/" to "/launcher". Used to display a dynamic launcher page for the same purposes.

API for URI Aliasing

Starcounter allows adding, modifying, listing, and deleting URI aliases using the following REST API (should be called on system port (by default 8181)):

• Adding and modifying a specific URI alias is done using PUT /sc/alias. The URI alias info should be in HTTP body with the following format:

{
  "HttpMethod": "",
  "FromUri": "",
  "ToUri": "",
  "Port": 0
}

for example, {"HttpMethod":"GET","FromUri":"/","ToUri":"/launcher","Port":8080}

• Listing all URI aliases is done using GET /sc/alias:

{  
  "Items":[  
    {  
      "HttpMethod": "GET",
      "FromUri": "/",
      "ToUri": "/launcher",
      "Port": 8080
    },
    {  
      "HttpMethod": "GET",
      "FromUri": "/myapp",
      "ToUri": "/myappalias",
      "Port": 8080
    }
  ]
}

Retrieving info about specific URI alias is done using GET /sc/alias/{?}/{?}/{?} where parameters are string httpMethod, long dbport, string fromUri. For example, http://127.0.0.1:8181/sc/alias/GET/8080//SomeFromUri

Deleting specific URI alias is done using DELETE /sc/alias/{?}/{?}/{?} where parameters are string httpMethod, long dbport, string fromUri. For example, http://127.0.0.1:8181/sc/alias/GET/8080//SomeFromUri

In comparison with redirects, URI aliasing API adds entries to network gateway configuration and preserved upon gateway/code-host restart.