[WICKET-4637] HeaderBufferingWebResponse#writeMetaData(WebResponse) throws ConcurrentModificationException when invoked in a link handler

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 1.5.7
• Component/s: wicket
• Labels: response
• Assignee: Unassigned
• Reporter: Bertrand Guay-Paquet
• Created: 03/Jul/12 13:42
• Updated: 04/Jul/12 14:38
• Resolved: 04/Jul/12 14:36

Description

This ticket follows from the email thread http://markmail.org/thread/uk5y4ddoopntmkgd

I use the following ReplaceHandlerException to trigger a redirect which restarts the response but does not discard the response's meta data (e.g. cookies).

/**

• Response restarting exception which does not reset the header meta data.
  */
  public class NonResettingRestartException extends ReplaceHandlerException {

public NonResettingRestartException(final Class<? extends Page> pageClass,
final PageParameters params, final RequestCycle cycle) {
super(createRequestHandler(pageClass, params), true);

Response response = cycle.getResponse();
if (response instanceof IMetaDataBufferingWebResponse)

{ IMetaDataBufferingWebResponse bufferingWebResponse = (IMetaDataBufferingWebResponse) response; WebResponse originalResponse = (WebResponse) cycle .getOriginalResponse(); bufferingWebResponse.writeMetaData(originalResponse); }

}

private static IRequestHandler createRequestHandler(
Class<? extends Page> pageClass, PageParameters params)

{ return new RenderPageRequestHandler(new PageProvider(pageClass, params)); }

}

When this exception is thrown from a link handler, a ConcurrentModificationException occurs with the following stack trace:
HeaderBufferingWebResponse.addCookie(Cookie) line: 72
BufferedWebResponse$AddCookieAction.invoke(WebResponse) line: 240
BufferedWebResponse.writeMetaData(WebResponse) line: 75
HeaderBufferingWebResponse.writeMetaData(WebResponse) line: 205
NonResettingRestartException.<init>(Class<Page>, PageParameters, RequestCycle) line: 28
LinkPage$4.onClick() line: 38

Analysis:
1) HeaderBufferingWebResponse delegates #writeMetaData() to its bufferedResponse (a BufferedWebResponse instance).
2) BufferedWebResponse iterates its action list with the single "AddCookieAction" and invoke()s it
3) BufferedWebResponse$AddCookieAction.invoke does "response.addCookie(cookie)"
4) The addCookie is executed with this==BufferedWebResponse from 2) which modifies the action list illegally