NIFI-13611 Reuse shared proxy header handling for Content Viewer

[exceptionfactory]

Summary

NIFI-13611 Refactors the ContentViewerController to use the shared RequestUriBuilder from nifi-web-servlet-shared to prepare the data reference URI. This avoids duplicate code and ensures consistent handling when NiFi is running behind a reverse proxy server.

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  • JDK 21

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[mcgilman]

Will review...

[mcgilman]

These changes do not work when clustered and behind a proxy. The incoming ref is the user facing URI. The previous behavior converted that URI into an "internal" URI so that a node could directly GET the content from another node in the cluster.

Interestingly, this behavior in this PR exposes an issue in handling the response of this GET because the response does not contain a content-disposition header and fails with an NPE.

3296 [APP] 2024-08-05 13:20:45,807 WARN [NiFi Web Server-191] org.apache.nifi.web.ContentViewerController Content retrieval failed
3297 java.lang.NullPointerException: Cannot invoke "String.indexOf(int)" because "headerValue" is null
3298     at org.springframework.http.ContentDisposition.tokenize(ContentDisposition.java:454)
3299     at org.springframework.http.ContentDisposition.parse(ContentDisposition.java:344)
3300     at org.apache.nifi.web.StandardNiFiContentAccess.getContent(StandardNiFiContentAccess.java:120)
3301     at org.apache.nifi.web.ContentViewerController.doGet(ContentViewerController.java:95)
3302     at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:527)
3303     at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:614)

[exceptionfactory]

Thanks for the feedback @mcgilman, I see the issue now with the URL changes for clustered requests. I will correct that issue and review the Content-Disposition handling.

[exceptionfactory]

Based on a separate discussion, I am going to close this pull request. With potential pending changes to the handling of custom content viewing, making incremental changes to the current Controller class is not necessary.