Target definition in xs-app.json

[sergey_korolev]

I understand that everybody knows it and it's probably my personal disorder. Nevertheless: could anyone share a clue on what "$1" exactly mean in xs-app.json route definition? Something like this:

{
"source": "^/some_url/(.*)$",
"target": "$1",
"destination": "some_destination"
}

[thomas_jung · Accepted solution]

The syntax route source/target is all regular expression based. Therefore I'd suggest just searching/reading up on the general concept of regular expression (particularly in the context of JavaScript as that is what the app router is written in). For example:

https://stackoverflow.com/questions/16702924/how-to-explain-1-2-in-javascript-when-using-regular-exp...

[sergey_korolev · Accepted solution]

Thanks Thomas,

Clear. Would be much helpful to add at least similar reference to support code examples in the documentation.

[former_member602655]

Hi Sergey

Basically $1 = (.*)$ for example /some_url/abc will make $1 = abc. A part of a pattern that can be enclosed in parentheses (...) is called a “capturing group” in regex.

Here are more examples and explanation from sap/approuter module:

https://www.npmjs.com/package/@sap/approuter#example-routes

Example routes

For example, if you have a configuration with the following destination:

[ { "name" : "app-1", "url" : "http://localhost:3001"} ] 

Here are some sample route configurations:

Route with a destination and no target

{ "source": "^/app1/(.*)$", "destination": "app-1"} 

Since there is no target property for that route, no path rewriting will take place.
If we receive /app1/a/b as a path, then a request to http://localhost:3001/app1/a/b is sent.
The source path is appended to the destination URL.

Route with case-insensitive matching

{ "source": { "path": "^/app1/(.*)$", "matchCase": false }, "destination": "app-1"} 

This example is much like the previous one,
but instead of accepting only paths starting with /app1/, we accept any variation of app1's case. </br>
That means if we receive /ApP1/a/B, then a request to http://localhost:3001/ApP1/a/B is sent. </br>
Note: The property matchCase has to be of type boolean. It is optional and has a default value true.

Route with a destination and a target

{ "source": "^/app1/(.*)$", "target": "/before/$1/after", "destination": "app-1"} 

Route with a service, a target and an endpoint

{ "source": "^/odata/v2/(.*)$", "target": "$1", "service": "com.sap.appbasic.country", "endpoint": "countryservice"} 

When a request with path /app1/a/b is received, the path rewriting is done according to the rules in the target property.
The request will be forwarded to http://localhost:3001/before/a/b/after.

Note: In regular expressions there is the term capturing group. If a part of a regular expression is surrounded with parenthesis, then what has been matched can be accessed using $ + the number of the group (starting from 1).
In the last example $1 is mapped to the (.*) part of the regular expression in the source property.

Route with dynamic destination and target

{ "source": "^/destination/([^/]+)/(.*)$", "target": "$2", "destination": "$1", "authenticationType": "xsuaa"} 

If you have a another destination configured:

[ { "name" : "myDestination", "url" : "http://localhost:3002"} ] 

when a request with the path /destination/myDestination/myTarget is received, the destination will be replaced with the url from “myDestination”, the target will get “myTarget” and the request will be redirected to http://localhost:3002/myTarget

Note: You can use a dynamic value (regex) or a static string for both destination and target values

Note: The approuter first looks for the destination name in the mainfest.yaml file, and if not found, looks for it in the destination service.

Hope it will help 🙂

[sergey_korolev]

Thanks Konrad for the detailed explanation

Cheers

[kammaje_cis]

wow... why is is this not part of documentation?

[Matthias_Kolley]

Is this documented (including examples) somewhere?

[former_member602655]

I am sorry for the late answer, I am not doing in SAP anymore. As I remember the soruce was README of sap/approuter package https://www.npmjs.com/package/@sap/approuter#example-routes