How to get rid of "500 Internal Server Error" using ui5-middleware-simpleproxy

Question

I built an SAPUI5 app using UI5 Tooling and now I'm having trouble connecting it to an OData service.

---

Since the real url to the OData Service is not public, let's just call it:

http://app99.sap.domain.com/sap/opu/odata/sap/Z_DOMAIN_SRV/

and opening it in my browser, adding $metadata?sap-language=DE at the end, works - I get the XML metadata document.

---

These are the files I tried to change to connect to the OData service:

• webapp
  • manifest.json
• package.json
• ui5.yaml

Adding a "dataSources"-object and a "models"-object in manifest.json

{
  "sap.app": {
    ...
    "dataSources": {
      "oDataService": {
        "uri": "/sap/opu/odata/sap/Z_DOMAIN_SRV/",
        "type": "OData"
      }
    }
  },
  "sap.ui5": {
    ...
    "models": {
      ...
      "": {
        "dataSource": "oDataService",
        "preload": true,
        "settings": {
          "useBatch": false
        }
      }
    },
    ...
  }
}

I also tried changing the "uri" value to the real link, http://app99.sap.domain.com/sap/opu/odata/sap/Z_DOMAIN_SRV/, but then I expectedly get a Cross-Origin error:

So I tried setting up a proxy by adding this to my package.json:

{
  ...
  "devDependencies": {
    "ui5-middleware-simpleproxy": "^0.5.1"
  },
  "ui5": {
    "dependencies": [
      "ui5-middleware-simpleproxy"
    ]
  },
  ...
}

and adding this to my ui5.yaml file:

...
server:
  customMiddleware:
    - name: ui5-middleware-simpleproxy
      mountPath: /sap/opu/odata/sap/Z_DOMAIN_SRV
      afterMiddleware: compression
      configuration:
        baseUri: "http://app99.sap.domain.com/sap/opu/odata/sap/Z_DOMAIN_SRV/"

hoping that now
http://localhost:8080/sap/opu/odata/sap/Z_DOMAIN_SRV/$metadata?sap-language=DE
would turn into
http://app99.sap.domain.com/sap/opu/odata/sap/Z_DOMAIN_SRV/$metadata?sap-language=DE
and it would work, but that isn't the case - I just get the error from the screenshot on top.

Any idea what I am missing?
I really want to make it work with this ui5-middleware-simpleproxy, because I don't want to start up two servers manually (the UI5 Tooling one and another one for the proxy). Currently I just need to do ui5 serve and everything works out of the box.

Answer 1

After changing the config in ui5.yaml it worked.
I don't quite understand how the relationship between mountPath and baseUri works and why it worked this way, but some problems can be solved with try and error like in my case :D

...
server:
  customMiddleware:
    - name: ui5-middleware-simpleproxy
      mountPath: /sap/opu/odata/sap
      afterMiddleware: compression
      configuration:
        baseUri: "http://app99.sap.domain.com/sap/opu/odata/sap"