Does any one success add express middleware in theia?

#1

I’m building a web app for multy users with one or more theia-backend behind reverse proxy.
The use case is that user open theia app from web app A, before thiea app loads in browser, I want to intercept the request and make some authentication.I searched the community as well as github, find that BackendApplicationContribution provide hook to acheive this.
When I add my own middleware, the browser apps goes to 404.
Below is my code

import {BackendApplicationContribution} from "@theia/core/lib/node";
import {MaybePromise} from "@theia/core";
import express = require('express');
import {injectable} from "inversify";

@injectable()
export class ThiauuobaAuthContribution implements BackendApplicationContribution {

    configure(app: express.Application): MaybePromise<void> {
        console.log("ThiauuobaAuthContribution.configure");
        const middleware = this.expressMiddleware.bind(this);
        app.use(middleware);
        console.log("after app.use")
        const routerStack = app._router.stack as any[];
        const layer = routerStack.splice(routerStack.findIndex(r => r.handler === middleware), 1);
        routerStack.splice(routerStack.findIndex(r => r.name === "expressInit") + 1, 0, ...layer);
    }

    protected expressMiddleware(req: express.Request, res: express.Response, next: express.NextFunction): void {
        console.log("ThiauuobaAuthContribution.expressMiddleware");
        if (this.validateToken()) {
            next()
        } else {
            console.log("ThiauuobaAuthContribution.expressMiddleware: invalid token");
            res.sendStatus(403);
        }
    }

    validateToken(): boolean {
        return true;
    }
}

I see https://github.com/eclipse-theia/theia/blob/master/packages/core/src/electron-node/token/electron-token-backend-contribution.ts use this hook, but my apps failed on this.
I also read this and this and this, none of them work.
Anyone helps? Thanks.

#2

Hi,

I’ve done something similar, and this worked for me (I simplified the code):

async configure(app: Application): Promise<void> {
  // Checks that the request has a valid access token
  // to access a secured path
  app.use(this.handleSecuredPaths);
  
  // This moves the middleware above to the sweet spot in the stack
  // where it can validate all the secured paths
  const stack = app._router.stack as any[];
  const item = stack.splice(stack.length - 1, 1)[0];
  stack.splice(4, 0, item);

  // register a bunch of paths to handle oauth
}

handleSecuredPaths = async (req: Request, res: Response, next: NextFunction) => {
  // check req has valid access token
  if(valid) {
   next();
  }
  else {
   res.redirect(loginUrl);
   return next("router");
  }
}

I also bind a WsRequestValidatorContribution to allow the web socket upgrade and connection.

Hope it helps!

#3

Hi, Hanksha
Appriciate for your reply, it helps.
My middleware works now, the root cause is that the contribition is not bind correctly.

    bind(ThiauuobaAuthContribution).toSelf().inSingletonScope();
    rebinbind(BackendApplicationContribution).toService(ThiauuobaAuthContribution);

Change the last line rebind to bind just fix this.

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