Strict servlet API: cannot call getOutputStream() after getWriter()

Question

i have an applet which will communicate with a servet ,  but got following error in the servlet
java.lang.IllegalStateException: strict servlet API: cannot call getOutputStream() after getWriter()
at weblogic.servlet.internal.ServletResponseImpl.getOutputStream(ServletResponseImpl.java:280)
at oracle.osl.lt.web.servlets.AudioServlet._processGetPlayList(AudioServlet.java:235)
at oracle.osl.lt.web.servlets.AudioServlet.doPost(AudioServlet.java:91)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.security.wls.filter.SSOSessionSynchronizationFilter.doFilter(SSOSessionSynchronizationFilter.java:276)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.security.jps.ee.http.JpsAbsFilter$1.run(JpsAbsFilter.java:111)
at java.security.AccessController.doPrivileged(Native Method)
at oracle.security.jps.util.JpsSubject.doAsPrivileged(JpsSubject.java:313)
at oracle.security.jps.ee.util.JpsPlatformUtil.runJaasMode(JpsPlatformUtil.java:413)
at oracle.security.jps.ee.http.JpsAbsFilter.runJaasMode(JpsAbsFilter.java:94)
at oracle.security.jps.ee.http.JpsAbsFilter.doFilter(JpsAbsFilter.java:161)
at oracle.security.jps.ee.http.JpsFilter.doFilter(JpsFilter.java:71)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.dms.servlet.DMSServletFilter.doFilter(DMSServletFilter.java:136)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:27)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3715)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3681)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2277)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2183)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1454)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:209)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:178)
SUBSYSTEM = HTTP USERID = <WLS Kernel> SEVERITY = Error THREAD = [ACTIVE] ExecuteThread: '1' for queue: 'weblogic.kernel.Default (self-tuning)' MSGID = BEA-101020 MACHINE = p1dvosl02 TXID = CONTEXTID = TIMESTAMP = 1318836952580
WatchAlarmType: AutomaticReset
WatchAlarmResetPeriod: 30000
>
*below _processGetPlayList() is called by doPost() of the servlet.*
seems the exception is thrown due to response.getOutputStream()?
any idea? thanks!!
private void _processGetPlayList(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
try {
ObjectOutputStream objectOut =
new ObjectOutputStream(new BufferedOutputStream(response.getOutputStream()));
try {
RichDataDTOExt richData = _getRichData(request);
if (richData == null) {
Log.web().debug(s7);
throw new ServletException(s7);
objectOut.writeObject(richData.getAudioRecordings().getAll(new ContentRefDTO[0]));
finally {
objectOut.close();
catch (IOException e) {
Log.web().error(e.getMessage());
throw new ServletException();
}

Answer 1

thanks for you reply. but seems we don't call getWriter() at all in our code.
actually this error only happen in our customer's env, no this issue in our development env.
besides using getOutputStream() and getWriter() simultaneously for same response, is this maybe related with some web server configuration?