Handled exception still being written to stdout

Question

I'm using jetty server for hosting my java app. I recently added request timeouts to kill requests that take too long. The file that logs my stdout (which normally should be empty) started to fill up with InterruptedException stack traces. Something like:

java.lang.InterruptedException
    ...... Some lower level code-lines of my project
    at com.mycompany.webapps.MyController.myMethod(MyController.java:252)
    at sun.reflect.GeneratedMethodAccessor67.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:816)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:738)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1651)
    at org.eclipse.jetty.servlets.UserAgentFilter.doFilter(UserAgentFilter.java:83)
    at org.eclipse.jetty.servlets.GzipFilter.doFilter(GzipFilter.java:310)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1622)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:549)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:568)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1111)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:478)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:183)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1045)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:199)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:109)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.handler.StatisticsHandler.handle(StatisticsHandler.java:159)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:462)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:279)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:232)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:534)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)

So, I added try-catch in myMethod (The highest method which is under my control):

@RequestMapping(value = "/myUrl/{id}", method = RequestMethod.GET)
@ResponseBody
public ResponseEntity<byte[]> myMethod(final HttpServletRequest request, @PathVariable final EncodedId id) {
  try {
    return serveImageRequest(request, sourceId.getId(), docId.getId(), dimensions.getWidth(), dimensions.getHeight());
  } catch (Exception ex) {
    log.error(ex.getMessage());
    return null;
  }
}

The log variable is a logger instance (using log4j) that writes the messages to a dedicated log file (and not the stdout). And still, messages are written to stdout. The only difference is that now they're also written to the log file. I can't find the reason for it to be written to stdout and I have to avoid it since the file that represents stdout does not have a rolling policy.

Answer 1

Turns out the root for the issue was in a 3rd party library which catches an exception and prints it stack trace to stdout. This is this was being printed although I caught and handled the exception.