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Editorial Team
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Asked: 2026-06-13T09:15:08+00:00

I am getting these errors when running a ToolTwist application in production. This seems

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I am getting these errors when running a ToolTwist application in production. This seems to happen ofter. What are the possible code errors that could lead to these stack traces?

2012-02-13 11:00:04,242 ERROR ServletUiModule - Error in Servlet tooltwist.ecommerce.RoutingUIM.doPost():
java.lang.IllegalStateException: Cannot forward after response has been committed
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:312)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
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1 Answer

  1. Editorial Team

    ANSWER A
    HttpServlet has two variations for getting the output stream – response.getWriter(), and response.getOutputStream(). In our case we use uh.getResponse() to get the response object.

    A few rules –

       1. One one of these approaches ca be used.

       2. The chosen method cannot be called twice.

       3. Once you have the output object, irrespective of whether you got a writer or an output stream, once you close it, you cannot use it again, nor get another one.

    In short, writing the servlets output is a one-shot operation. You get the object, you write, your return from the servlet.

    ANSWER B
    I seem to recall there may also be a situation where you are writing to the output, but then the error handler kicks in to handle an exception, and the error page has a problem creating further output. Any page used to handle errors must specifically have the errorpage tag (i don’t recall exactly the tag).

    ANSWER C
    Once you have written something to the servlet’s output, you cannot forward to another page without getting this error.

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