UIX 2.1.7: java.lang.IllegalStateException

Question

Hi all,
we have an UIX page that shows a BC4J view object and offers to export the VO data to PDF. When the user clicks a button, the page is submitted and the UIX event handler uses a 3rd party library to create a byte array containing the PDF data. Still in the event handler, we retrieve the HttpServletResponse from the BajaContext and write the PDF data into the response's output stream.
So far so good. However, each time we do this, the following exception is thrown:
java.lang.IllegalStateException: Response is already committed!
     at com.evermind.server.http.EvermindHttpServletResponse.setContentType(EvermindHttpServletResponse.java:1027)
     at oracle.cabo.ui.ServletRenderingContext.prepareResponse(Unknown Source)
     at oracle.cabo.servlet.ui.UINodePageRenderer.renderPage(Unknown Source)
     at oracle.cabo.servlet.AbstractPageBroker.renderPage(Unknown Source)
     at oracle.cabo.servlet.PageBrokerHandler.handleRequest(Unknown Source)
     at oracle.cabo.servlet.UIXServlet.doGet(Unknown Source)
     at oracle.cabo.servlet.UIXServlet.doPost(Unknown Source)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:721)
     at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:306)
     at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:767)
     at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:259)
     at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:106)
     at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:803)
     at java.lang.Thread.run(Thread.java:534)
Usually, we ignore the exception, because it only appears in the server log and the browser receives and displays the PDF document anyway. However, when it reaches a certain size, the server appends the exception trace to the servlet response and the PDF becomes corrupt.
Has anyone an idea how to suppress the exception? Is this the preferred way to write dynamically created data to the response without the indirection of creating a temporary file and downloading it?
Thanks a lot for any hint!
Markus.

Answer 1

Hi Markus -
I believe the solution is to use oracle.cabo.servlet.util.RedirectUtils.getResponseCompletePage() to retrieve that Page that you will return from your event handler. This method returns a special Page that tells UIX to not render any additional content.
Andy