@sap-ux/backend-proxy-middleware

@sap-ux/backend-proxy-middleware

The @sap-ux/backend-proxy-middleware is a Custom UI5 Server Middleware for proxying requests to backend servers. The middleware is agnostic to running in local environments and SAP Business Application Studio. Additionally, if credentials are maintained with the SAP Fiori tools then these will be used.

It can be used either with the ui5 serve or the fiori run commands.

Configuration Options

backend

Option	Type	Description
url	string mandatory (local)	URL pointing to the backend system is mandatory, unless a destination is provided and the proxy is running on SAP Business Application Studio. Developers can append additional URL parameters if necessary
destination	string mandatory (if no url)	Required if the backend system is available as destination in SAP Business Application Studio.
destinationInstance	string optional	If a destination needs to be read by a specific instance of a destination service then you need to provide the id of the service as optional property destinationInstance.
path	string mandatory	Path that is to be proxied
pathReplace	string optional	If provided then the path will be replaced with this value before forwarding
client	string optional	sap-client parameter
scp	boolean optional	If set to true the proxy will execute the required OAuth routine for the ABAP environment on SAP BTP
apiHub	boolean optional	If set to true then the proxy will connect to the SAP API Business Hub
proxy	string optional	If set then it will override the proxy settings from node.
authenticationType	string optional	Authentication mechanism to be used in VSCode. Currently supported: "ReentranceTicket"

Additional optional experimental property bsp (type string): The BSP property is only needed for the FLP Embedded Flow. The property refers to the BSP Application Name. In that case, we need to redirect the manifest.appdescr request to the local manifest.json in order to overwrite the deployed application with the local one.

options

Optional object that can be used to directly set options of the used http-proxy-middleware modules (https://www.npmjs.com/package/http-proxy-middleware#http-proxy-middleware-options). Note: only declarative options (i.e. no functions) are supported.

Configuration Examples

Connecting to a backend system

Executing ui5 serve in your project with the configuration below in the ui5.yaml file would forward any request starting with the path parameter to the provided backend url.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /sap
      url: https://my.backend.example:1234

Connecting to a backend system with destination

If working in SAP Business Application Studio and the backend is configured as destination then you can also provide the destination in the configuration. If a destination needs to be read by a specific instance of a destination service then you need to provide the id of the service as optional property destinationInstance.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /sap
      destination: my_example_destination

Connecting to a backend system with destination and principal propagation

If the backend destination is configured to use principal propagation, then in some cases the requests might fail. If this occurs then you will need to set the optional property xfwd to true. This will add the x-forwared headers to the proxy requests.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /sap
      destination: my_example_destination
    options:
      xfwd: true

Connecting to the SAP Business Technology Platform

If you want to connect to an ABAP Environment on SAP Business Technology Platform then you will need to set the optional property scp to true. For any other target, remove this property or set it to false.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /sap
      url: https://my.steampunk.example:1234
      scp: true

Connecting to the SAP API Business Hub

If you want to connect to the SAP API Business Hub then you will need to set the optional property apiHub to true, and set the corresponding path and url, e.g.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /s4hanacloud
      url: https://api.sap.com
      apiHub: true

Proxying WebSockets

If you want the proxy to handle also WebSockets, then you need to set the optional property ws to true, e.g.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /sap
      url: https://my.backend.example:1234
    options:
      ws: true

Changing the path to which a request is proxied

If you want to configure the proxy to send requests from a certain path /services/odata to your backend (local url or destination) with a specified entry path /my/entry/path. Then you need to do the following:

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /services/odata
      pathReplace: /my/entry/path
      url: https://my.backend.example:1234
      destination: my_example_destination

Providing Proxy Configuration

By default the backend-proxy-middleware will read the proxy configuration from the OS environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY or from the Node.js environment variables proxy, https-proxy and noproxy. If those variables are not set, then you can also provide the proxy configuration in the ui5.yaml file.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    proxy: https://myproxy.example:8443
    backend:
      path: /sap
      url: https://my.backend.example:1234

Please note: if you want to exclude any domains from the proxy then you will need to set the noproxy variable. E.g. if you want to exclude the https://my.backend.example:1234 from the proxy you will need to set noproxy to npm config set noproxy ".backend.example". Note the leading ., if you provide only backend.example, then it will not work.

Proxying Multiple Paths Backends

To connect to multiple backend or multiple paths of a backend, use multiple instances of the middleware.

- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /my/path
      url: https://my.backend.example:1234
- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /my/other/path
      url: https://my.backend.example:1234
- name: backend-proxy-middleware
  afterMiddleware: compression
  configuration:
    backend:
      path: /my/path
      url: https://other.backend.example:1234

Programmatic Usage

Alternatively you can only use the underlying proxy function, e.g. for the case when you want to use the backend-proxy-middleware functionality in your express server.

import { createProxy } from '@sap-ux/backend-proxy-middleware';
const proxy = createProxy(backend, options);

• config - The backend configuration
• options - Options of the http-proxy-middleware

Keywords

• Backend Proxy Middleware
• Fiori tools
• Fiori elements
• SAP UI5