[WICKET-349] ListView can't undo changes to model

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.5, 1.2.6
• Fix Version/s: 1.2.7, 1.3.0-beta4
• Component/s: wicket
• Environment: WinXP, Tomcat 5.5.
• Assignee: Johan Compagner
• Reporter: Kent Tong
• Created: 03/Mar/07 13:08
• Updated: 03/Oct/07 15:50
• Resolved: 03/Oct/07 15:50

Description

Given the code below (adapted from the guestbook example):

Form form = new Form("form") {
protected void onSubmit()

{ List comments = listView.getList(); listView.modelChanging(); comments.add(new Comment(comment, new Date())); comment = ""; listView.modelChanged(); }

};

Perform the steps:
1) add "a" to the ListView and submit, bringing the page to version 1.
2) add "b" to the ListView and submit, bringing the page to version 2.
3) add "c" to the ListView and submit, bringing the page to version 3.
4) press Back twice.
5) add "x" to the ListView and submit. This will try to revert the page back to version 1. But it will fail with an IllegalStateException (full stack trace is shown below).

This is because at step 3, the ListView contains two items: "a" and "b". Calling modelChanging() will store the model (a list containing "a" and "b") into a ModelChange object for later undo. The problem is, when this action is undone, ModelChange.undo() will call setModel() on the ListView, which will call removeAll() on itself. This will leave the ListView in a state different from the original (containing "a" and "b" items). This is not a problem if the ListView was to be rendered immediately (then it would create the items again). But in this case, the next step is to further undo the adding of item "b". However, the item's parent has just been set to null by removeAll(). This causes Component.remove() to throw an exception.

Full stack trace is here:
Unexpected RuntimeException

Root cause:

java.lang.IllegalStateException: Cannot remove [MarkupContainer [Component id = 1, page = <No Page>, path = 1.ListItem]] from null parent!
at wicket.Component.remove(Component.java:1469)
at wicket.version.undo.Add.undo(Add.java:81)
at wicket.version.undo.ChangeList.undo(ChangeList.java:93)
at wicket.version.undo.UndoPageVersionManager.undo(UndoPageVersionManager.java:217)
at wicket.version.undo.UndoPageVersionManager.getVersion(UndoPageVersionManager.java:167)
at wicket.Page.getVersion(Page.java:589)
at wicket.PageMap.get(PageMap.java:461)
at wicket.Session.getPage(Session.java:447)
at wicket.request.compound.DefaultRequestTargetResolverStrategy.resolveRenderedPage(DefaultRequestTargetResolverStrategy.java:215)
at wicket.request.compound.DefaultRequestTargetResolverStrategy.resolve(DefaultRequestTargetResolverStrategy.java:153)
at wicket.request.compound.AbstractCompoundRequestCycleProcessor.resolve(AbstractCompoundRequestCycleProcessor.java:48)
at wicket.RequestCycle.step(RequestCycle.java:992)
at wicket.RequestCycle.steps(RequestCycle.java:1084)
at wicket.RequestCycle.request(RequestCycle.java:454)
at wicket.protocol.http.WicketServlet.doGet(WicketServlet.java:219)
at wicket.protocol.http.WicketServlet.doPost(WicketServlet.java:262)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:825)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:738)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:526)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)