如何获取Spring REST文件下载以返回404？

Question

I have a simple REST API, with file download capability. The endpoint is defined like this:

@RequestMapping(value = "/myapi/files/{fileName}", 
    method = RequestMethod.GET, 
    produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE })
@ResponseBody FileSystemResource downloadFile(String fileName) 
    throws UnknownFileException;

The meat of the implementation method is currently:

try {
    FileSystemResource fsr = 
        new FileSystemResource("C:/myfiles/" + fileName + "." + suffix);
} catch (Throwable e) {
    throw new UnknownFileException();
}

And I have a simple exception handler, which returns a 404.

@ExceptionHandler(UnknownFileException.class)
@ResponseBody
@ResponseStatus(HttpStatus.NOT_FOUND)
public ErrorMessage handleUnknownFileException(
        UnknownFileException e, HttpServletRequest req) {
    return new ErrorMessage(e);
}

These exception handlers work nicely for other operations which return XML/JSON responses. The trouble I have is that when this method throws an exception, it looks like it's being intercepted by the Spring ResourceHttpMessageConverter, which is throwing a 500 error back to the client.

So my question is how I might ensure that an HTTP 404 is returned instead of the generic 500?

Edit - Stack trace below for what it's worth:

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is com.....UnknownFileException: Unable to find file
        org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:894)
        org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
        org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
        org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
        org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:88)
        org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

Answer 1

You probably want to do something like this:

response.setStatus(HttpStatus.NOT_FOUND.value());

Of course, you would need to add the HttpServletResponse to the method declaration.