[jira] [Created] (WICKET-6600) Error logging in AjaxRequestHandler is too strict

["Gert-Jan Schouten (JIRA)" <ji...@apache.org>]

Gert-Jan Schouten created WICKET-6600:
-----------------------------------------

             Summary: Error logging in AjaxRequestHandler is too strict
                 Key: WICKET-6600
                 URL: https://issues.apache.org/jira/browse/WICKET-6600
             Project: Wicket
          Issue Type: Improvement
          Components: wicket-core
    Affects Versions: 8.0.0
            Reporter: Gert-Jan Schouten


As a result of these three commits, [one|[https://github.com/apache/wicket/commit/dec1293da853357f483eadec4616c9758ea025f9#diff-8964e43671328bf6f9b1d75703103db8],] [two|[https://github.com/apache/wicket/commit/3be55cf5a24982cfca400225aabb6c4296859a7d#diff-8964e43671328bf6f9b1d75703103db8]|https://github.com/apache/wicket/commit/3be55cf5a24982cfca400225aabb6c4296859a7d#diff-8964e43671328bf6f9b1d75703103db8],] and [three|[https://github.com/apache/wicket/commit/830fb15c333ad6099f466b2344a84b513690db86#diff-8964e43671328bf6f9b1d75703103db8],] Wicket now logs a stacktrace on error level if you add something to the AjaxRequestTarget that has been removed from the page. I don't think this is a good idea, because you're not always in control of what happens in an Ajax call. Imagine, for example, the following scenario:
{code:java}
public abstract class MyPanel extends Panel {

    public MyPanel(String id) {
        super(id);

        this.setOutputMarkupId(true);

        this.add(new AjaxLink("myLink") {
            public void onClick(final AjaxRequestTarget target) {
                this.executeImportantWork(target);

                //Display something nice on this Panel
                //...

                target.add(MyPanel.this); //In order to show the nice things
            }
        });
    }

    protected abstract void executeImportantWork(AjaxRequestTarget target);
}

{code}
Now, what if the user of MyPanel actually adds it to the Page and then, in executeImportantWork, removes it and replaces it with smth else? Then, you get an error in the log, everytime someone clicks myLink.

In this case, it could be fixed by adding MyPanel.this to the target *before* calling executeImportantWork, in which case you also get something in the log, but without stacktrace and on WARN level, namely this: "Component not rendered because it was already removed from page", but this is far less invasive than the scary stacktrace on ERROR level.

I suggest changing the level of the message to WARN and removing the stacktrace.



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