This exception basically tells you that Rewrite tries to forward the request to some internal URL (because one of your rules matched) but isn’t able to do so because someone has committed the response before. The response gets committed for example if someone calls HttpServletResponse.getOutputStream() and starts writing to the client.
These issues are very difficult to debug. You could try to enable DEBUG/TRACE logging level for Rewrite to find out more. Or you could set a break point in Rewrite’s HttpRewriteResultHandler which performs the forward and check the properties of HttpServletResponse. You can also try to use method break points for relevant methods on HttpServletResponse to find the place where the response gets committed.
I hope this helps
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