Server servlet context path omitted when run with X-Forwarded-Prefix

[joaonatalio]

Describe the bug

The server servlet context path is omitted when Springdoc is running behind a reverse proxy and an X-Forwarded-Prefix header is present. The issue was originally reported in #2058 but dismissed, lacking some clarity in the reproduction.
Please see the new working example in https://github.com/joaonatalio/springdoc-context-path-bug demonstrating the issue for spring-boot-parent:3.0.2 and springdoc-openapi-starter-webmvc-ui:2.0.2.

In application.yml we have servlet.forward-headers-strategy: framework defined so that our app processes the incoming X-Forwarded-* from our reverse proxy, like it's suggested in springdoc's 2.x FAQ.

In our case we defined the following springdoc config to show the problematic redirect behaviour more clearly:

springdoc:
  api-docs:
    path: /swagger/api-docs
  swagger-ui:
    path: /swagger/swagger-ui.html

To Reproduce
(For spring-boot:3.0.2 and springdoc-openapi-starter-webmvc-ui:2.0.2)

1. Run Spring Boot application jar from local machine: java -jar target/springdoc-context-path-1.0-SNAPSHOT.jar

2. Navigate to http://localhost:8080/petstore/swagger/swagger-ui.html to view petstore's swagger-ui, all resources are loaded correctly since it redirects the initial request to the expected url http://localhost:8080/petstore/swagger/swagger-ui/index.html.

3. Stop application and run docker compose up which uses nginx X-Forwarded-Prefix header with fixed /api value, just for demo purposes.

4. Navigate to http://localhost:8080/api/petstore/swagger/swagger-ui.html. We're redirected to http://localhost:8080/api/swagger/swagger-ui/index.html, taking into account the passed X-Forwarded-Prefix header, but omitting the servlet context path entirely.

Expected behavior

In step 4) the swagger-ui.html should redirect to http://localhost:8080/api/petstore/swagger/swagger-ui/index.html, taking into account the passed X-Forwarded-Prefix and the servlet context path.

[bnasslahsen]

@joaonatalio,

It's all about your settings ...And your description...
You should just pass well X-Forwarded-Prefix ...

For #2058 the answer is correct, as he was just expecting the access to swagger-config

For your case, this is the fix, because your are looking for. You want also display the UI.

And last, it's not a bug :)

[joaonatalio]

@bnasslahsen the point of the example was to forward only the /api prefix in X-Forwarded-Prefix which is perfectly valid, petstore is the name of servlet context and part of the original url and, as such, it should be handled by springdoc as expected... Given your suggestion, the expected url to be forwarded to would be http://localhost:8080/api/petstore/petstore/swagger/swagger-ui/index.html if this issue didn't exist.
To be fair I'm not sure if the issue relies in springdoc or swagger-ui itself, but it definitely is there, but I don't have the full context and require a deeper analysis on the team's part.

If you still don't get mine and @heuristicservices 's point, I would kindly suggest to get an extra reviewer here.

[bnasslahsen]

@joaonatalio,

If you want forward /api only, then review your nginx rules.
You got your answer to have the expected result ...

The problem, is you are setting wrong X-Forwarded-Prefix. I hope you will understand.
We estimate, there will be no more efforts spent on this ticket.