WICKET-6525 restored check for onsubmit on form

which was lost in WICKET_6348

wicket-core/src/main/java/org/apache/wicket/markup/html/form/SubmitLink.java

@@ -207,9 +207,18 @@ protected CharSequence getTriggerJavaScript()
 			// find the root form - the one we are really going to submit
 			Form<?> root = getForm().getRootForm();
 
+			StringBuilder script = new StringBuilder();
+			if (shouldInvokeJavaScriptFormOnsubmit())
+			{
+				script.append(String.format("var ff=document.getElementById('%s');", getForm().getMarkupId()));
+				script.append("if (typeof ff.onsubmit === 'function' && ff.onsubmit() == false) return false;");
+			}
+
 			CharSequence url = urlForListener(new PageParameters());
-
-			return root.getJsForListenerUrl(url);
+			script.append(root.getJsForListenerUrl(url));
+			script.append("return false;");
+
+			return script;
 		}
 		else
 		{

wicket-examples/src/main/java/org/apache/wicket/examples/compref/SubmitLinkPage.html

@@ -11,13 +11,13 @@ <h1>wicket.markup.html.form.SubmitLink</h1>
 
 	<p>
 	A SubmitLink is a special link that acts like a submit button.
-	It can be inside the form component or inside the form component.
+	It can be inside the form component or outside the form component.
 	</p>
 	<p>
-	 <form wicket:id="form">
+	 <form wicket:id="form" onsubmit="return confirm('Do you really want to submit?');">
 	  <a wicket:id="internal">Internal SubmitLink</a>
 	 </form>
-	  <a wicket:id="external">External SubmitLink</a>
+	  <a wicket:id="external">External SubmitLink with confirmation</a>
 	 <span wicket:id="feedback">feedbackmessages will be put here</span>
 	</p>
     <span wicket:id="explainPanel">panel contents come here</span>

wicket-examples/src/main/java/org/apache/wicket/examples/compref/SubmitLinkPage.java

@@ -44,6 +44,12 @@ public SubmitLinkPage()
 
 		SubmitLink internal = new SubmitLink("internal")
 		{
+			@Override
+			protected boolean shouldInvokeJavaScriptFormOnsubmit()
+			{
+				return false;
+			}
+
 			@Override
 			public void onSubmit()
 			{