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Use the SAP Cloud SDK in the Browser

The SAP Cloud SDK for JavaScript can be used both as a backend and frontend library when used in a browser. Because of the specifics of a browser environment, some features might be unavailable. To help you get up and running faster in a browser, we'll outline the main steps and caveats of using SAP Cloud SDK on the frontend. Both Angular and React applications are used to illustrate the usage.

Prerequisite​

A frontend application set up using either of the following:

  • Angular application via ng new my-app
  • React application via npx create-react-app my-app. Rewire the create-react-app project using react-app-rewired or other alternatives. This creates a config-overrides.js file in the root directory which can be used to override the settings for various webpack modules.

Include the SAP Cloud SDK​

The example below uses the business partner API. To learn how to generate an API client from a service definition, refer to this article.

//In the .html part of the component
<button (click)="callApi()">Click me!</button>

//In the .ts part of the component
import { businessPartnerService } from './generated/business-partner-service';

const { businessPartnerApi } = businessPartnerService();

async function callApi(){
  const result = await businessPartnerApi.requestBuilder().getAll().execute(myDest)
  console.log(result)
}
note

For the destination lookup, the SAP Cloud SDK relies on Node.js functionality, e.g., process.env. However, the request building, execution, and result parsing do not require any Node.js modules and can be used on the frontend. Hence, create the destination variable myDest manually.

Executing npm run build will result in compilation errors of the kind shown below:

Module not found: Error: Can't resolve 'https' in

Check out the workaround for resolving such errors.

Run Locally​

As discussed above, the myDest can not be fetched via the destination service. Create and pass the variable when running locally.

import { Destination } from '@sap-cloud-sdk/connectivity';

const myDest: Destination = {
  url: 'https://my123456.s4hana.ondemand.com',
  username: 'myUser',
  password: 'myPassowrd'
};

Executing npm run serve compiles the project and hosts the application on a local server.

info

All modern browsers block requests triggered from a browser to a remote system to ensure same origin policy. One simple way to overcome this issue locally is to disable the web security of the browser temporarily (e.g. --disable-web-security for Chrome). Alternatively, create a second localhost proxy server that adds the access-allow-origin-header to the request.

Run on SAP BTP, Cloud Foundry Environment​

For productive usage, the methods mentioned above for running locally are not needed. Configure the xs-app.json file of the approuter with an entry as shown below:

{
  "source": "/REMOTE_SYSTEM_IDENTIFIER/(.*)",
  "target": "/$1",
  "destination": "DESTINATION_NAME_ON_CF"
}

and then, in the application, define the destination as follows:

import { Destination } from '@sap-cloud-sdk/connectivity';

const myDest: Destination = {
  url: '/REMOTE_SYSTEM_IDENTIFIER'
};

The created request to /REMOTE_SYSTEM_IDENTIFIER/sap/opu/odata/sap/API_BUSINESS_PARTNER/A_BusinessPartner will be matched by the approuter and the destination with the given URL and credentials is used.

The approuter establishes a session with the client (browser) using a session cookie. This session contains elements like the redirect URL, OAuth token, OAuth scopes, etc. OAuth token is a JSON Web Token (JWT) that is fetched from the UAA and forwarded to backend services in the Authorization header. The client never gets this token.

For a detailed understanding of session handling in the application router, refer to the documentation here.

note

This approach does not support principal propagation to on-premise systems. For this, you need a JWT and need to include the proper header fields defining the user. See the documentation on on-premise systems for details.

info

With webpack, it is possible to load resources for local or productive usage. Using such a switch, you can adjust the value of the destination for the two cases.

Workaround​

Webpack version 5 removed the automatic node.js polyfills and they need to be added manually. An error message during the compilation from TS to JS provides a hint on how to achieve that.

Angular​

  • Add the corresponding library of the node.js core modules or the browserified version in devDependencies in your package.json file

  • Include @angular-builders/custom-webpack in devDependencies

  • Create a custom webpack configuration named node-webpack.config.js and list the node modules

    module.exports = {
      resolve: {
        alias: {
          process: 'process/browser',
          https: 'agent-base',
          http: 'agent-base'
        },
        fallback: {
          url: false,
          os: false,
          assert: false,
          constants: false,
          zlib: false,
          path: false,
          http: false,
          util: require.resolve('util/'),
          process: require.resolve('process/browser'),
          stream: require.resolve('stream-browserify'),
          buffer: require.resolve('buffer'),
          crypto: require.resolve('crypto-browserify'),
          https: require.resolve('https-browserify')
        }
      },
      plugins: [new ProvidePlugin({ process: 'process/browser' })]
    };

  • In the angular.json file, adjust the build target to use the custom builder and set path to the custom config node-webpack.config.js defined above

    "build": {
      "builder": "@angular-builders/custom-webpack:browser",
      "options": {
        "customWebpackConfig": {
          "path": "./node-webpack.config.js"
        }
      }

  • In the angular.json file, adjust the serve target to use the custom builder as well

    "serve": {
      "builder": "@angular-builders/custom-webpack:dev-server",

  • In the package.json file, exclude the node modules that do not exist in the browser

    "browser": {
      "fs": false,
      "net": false,
      "tls": false
    }

  • Proxy any requests to your API server in development by adding a proxy.config.json file in /src folder This avoids the CORS issues.

    {
      "/api/*": {
        "target": "REMOTE_SYSTEM_IDENTIFIER",
        "secure": true,
        "logLevel": "debug",
        "changeOrigin": true
      }
    }

    Since the base path has been set in the proxy config, change the value of the url property in myDest to /. In the angular.json file, adjust the serve options to include proxyConfig.

    "proxyConfig": "src/proxy.conf.json"

React​

  • Add the corresponding library of the core node.js modules in devDependencies in your package.json file. Add the react-app-rewired dependency and adjust the existing calls to react-scripts in npm scripts for start, build and test

    "start": "react-app-rewired start"

  • In the config-overrides.js file, list the core node modules

    module.exports = function override(config, env) {
      config.ignoreWarnings = [/Failed to parse source map/];
      config.resolve.alias = {
        https: 'agent-base',
        http: 'agent-base'
      };
      config.resolve.fallback = {
        os: false,
        url: false,
        https: false,
        http: false,
        fs: false,
        path: false,
        assert: false,
        zlib: false,
        tls: false,
        net: false,
        constants: false,
        util: require.resolve('util'),
        process: require.resolve('process/browser'),
        stream: require.resolve('stream-browserify'),
        buffer: require.resolve('buffer'),
        console: require.resolve('console-browserify'),
        crypto: require.resolve('crypto-browserify'),
        https: require.resolve('https-browserify')
      };
      config.plugins = [
        ...config.plugins,
        new ProvidePlugin({
          Buffer: ['buffer', 'Buffer']
        }),
        new ProvidePlugin({
          process: 'process/browser'
        }),
        new NormalModuleReplacementPlugin(/^node:/, resource => {
          resource.request = resource.request.replace(/^node:/, '');
        })
      ];

      return config;
    };

  • Proxy any requests to your API server in development by adding a proxy field to the package.json file. This avoids the CORS issues.

    "proxy": "REMOTE_SYSTEM_IDENTIFIER",

    Since the base path has been set in the proxy, change the value of the url property in myDest to /

    caution

    This proxy is only for development. You need to ensure that API URLs point to the right target in production.

Now, the project should build and run locally.