WICKET-7144: form component panel ajax update improvement

wicket-core/src/main/java/org/apache/wicket/ajax/form/AjaxFormComponentUpdatingBehavior.java

@@ -25,8 +25,8 @@
 import org.apache.wicket.ajax.AjaxRequestTarget;
 import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
 import org.apache.wicket.ajax.attributes.AjaxRequestAttributes.Method;
-import org.apache.wicket.core.request.handler.IPartialPageRequestHandler;
 import org.apache.wicket.markup.html.form.FormComponent;
+import org.apache.wicket.markup.html.form.FormComponentPanel;
 import org.apache.wicket.markup.html.form.validation.IFormValidator;
 import org.apache.wicket.util.lang.Args;
 import org.danekja.java.util.function.serializable.SerializableConsumer;
@@ -121,6 +121,11 @@ protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
 		super.updateAjaxAttributes(attributes);
 
 		attributes.setMethod(Method.POST);
+
+		if (getComponent() instanceof FormComponentPanel<?> formComponentPanel) {
+			formComponentPanel.wantChildrenToProcessInputInAjaxUpdate();
+			attributes.setSerializeRecursively(true);
+		}
 	}
 
 	@Override
@@ -135,6 +140,12 @@ protected final void onEvent(final AjaxRequestTarget target)
 
 		try
 		{
+			if (formComponent instanceof FormComponentPanel<?> formComponentPanel) {
+				if (formComponentPanel.wantChildrenToProcessInputInAjaxUpdate()) {
+					((FormComponentPanel<?>)formComponent).processInputOfChildren();
+				}
+			}
+
 			formComponent.inputChanged();
 			formComponent.validate();
 			if (formComponent.isValid())

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

@@ -172,4 +172,38 @@ public void clearInput()
 			}
 		});
 	}
+
+	/**
+	 * By returning <code>true</code> (and implementing {@link #processInputOfChildren()}) it will be possible to add a
+	 * {@link org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior AjaxFormComponentUpdatingBehavior} to this
+	 * panel, and be able to access the updated model object of this panel in that behavior.
+	 *
+	 * @return <code>true</code> if this panel wants children to process the input on an Ajax update, <code>false</code>
+	 * otherwise.
+	 */
+	public boolean wantChildrenToProcessInputInAjaxUpdate() {
+		return false;
+	}
+
+	/**
+	 * Called by {@link org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior AjaxFormComponentUpdatingBehavior}
+	 * if {@link #wantChildrenToProcessInputInAjaxUpdate()} returns <code>true</code>. Each nested form component must
+	 * be asked to process its input. You should use {@link #processInputOfChild(FormComponent)} as this method takes
+	 * nested <code>FormComponentPanel</code>s that also want their children to process the input into account.
+	 */
+	public void processInputOfChildren() {
+	}
+
+	/**
+	 * Tell the given child component to process its input. If the child component is a <code>FormComponentPanel</code>
+	 * that wants its children to process their input, it will be told to do so.
+	 *
+	 * @param child the component to tell to process its children.
+	 */
+	protected final void processInputOfChild(FormComponent<?> child) {
+		if (child instanceof FormComponentPanel<?> formComponentPanel && formComponentPanel.wantChildrenToProcessInputInAjaxUpdate()) {
+			formComponentPanel.processInputOfChildren();
+		}
+		child.processInput();
+	}
 }

wicket-examples/src/main/java/org/apache/wicket/examples/forminput/Multiply.java

@@ -16,6 +16,7 @@
  */
 package org.apache.wicket.examples.forminput;
 
+import org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior;
 import org.apache.wicket.markup.html.form.FormComponentPanel;
 import org.apache.wicket.markup.html.form.TextField;
 import org.apache.wicket.model.IModel;
@@ -29,7 +30,12 @@
  * with the lhs and rhs. You would use this component's model (value) primarily to write the result
  * to some object, without ever directly setting it in code yourself.
  * </p>
- * 
+ * <p>
+ * <strong>Ajaxifying a Multiply</strong>:
+ * If you want to update this component with an {@link AjaxFormComponentUpdatingBehavior}, you have to override
+ * {@link #wantChildrenToProcessInputInAjaxUpdate()} and return <code>true</code>.
+ * </p>
+ *
  * @author eelcohillenius
  */
 public class Multiply extends FormComponentPanel<Integer>
@@ -110,6 +116,13 @@ private void init()
 		right.setRequired(true);
 	}
 
+	@Override
+	public void processInputOfChildren()
+	{
+		processInputOfChild(left);
+		processInputOfChild(right);
+	}
+
 	/**
 	 * @see org.apache.wicket.markup.html.form.FormComponent#convertInput()
 	 */

wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/form/datetime/AbstractDateTimeField.java

@@ -35,26 +35,11 @@
  * Works on a {@link java.time.temporal.Temporal} object, aggregating a {@link LocalDateTextField} and a {@link TimeField}.
  * <p>
  * <strong>Ajaxifying an AbstractDateTimeField</strong>:
- * If you want to update this component with an {@link AjaxFormComponentUpdatingBehavior}, you have to attach it
- * to the contained components by overriding {@link #newDateField(String, IModel)}:
- * 
- * <pre>{@code
- *  DateTimeField dateTimeField = new DateTimeField(...) {
- *    protected DateTextField newDateTextField(String id, PropertyModel<Date> dateFieldModel)
- *    {
- *      DateTextField dateField = super.newDateTextField(id, dateFieldModel);     
- *      dateField.add(new AjaxFormComponentUpdatingBehavior("change") {
- *        protected void onUpdate(AjaxRequestTarget target) {
- *          processInput(); // let DateTimeField process input too
+ * If you want to update this component with an {@link AjaxFormComponentUpdatingBehavior}, you have to override
+ * {@link #wantChildrenToProcessInputInAjaxUpdate()} and return <code>true</code>, and override
+ * {@link #newTimeField(String, IModel)} and return a subclass of <code>TimeField</code> that also returns
+ * <code>true</code> from <code>wantChildrenToProcessInputInAjaxUpdate()</code>.
  *
- *          ...
- *        }
- *      });
- *      return recorder;
- *    }
- *  }
- * }</pre>
- * 
  * @author eelcohillenius
  */
 abstract class AbstractDateTimeField<T extends Temporal> extends FormComponentPanel<T>
@@ -140,6 +125,13 @@ public String getInput()
 		return String.format("%s, %s", localDateField.getInput(), timeField.getInput());
 	}
 
+	@Override
+	public void processInputOfChildren()
+	{
+		processInputOfChild(localDateField);
+		processInputOfChild(timeField);
+	}
+
 	/**
 	 * Sets the converted input, which is an instance of {@link Date}, possibly null. It combines
 	 * the inputs of the nested date, hours, minutes and am/pm fields and constructs a date from it.

wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/form/datetime/TimeField.java

@@ -26,6 +26,7 @@
 import java.util.Arrays;
 import java.util.Locale;
 
+import org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior;
 import org.apache.wicket.core.util.string.CssUtils;
 import org.apache.wicket.markup.ComponentTag;
 import org.apache.wicket.markup.html.basic.Label;
@@ -44,7 +45,11 @@
  * AM/PM field. The format (12h/24h) of the hours field depends on the time format of this
  * {@link TimeField}'s {@link Locale}, as does the visibility of the AM/PM field (see
  * {@link TimeField#use12HourFormat}).
- * 
+ * <p>
+ * <strong>Ajaxifying a TimeField</strong>:
+ * If you want to update this component with an {@link AjaxFormComponentUpdatingBehavior}, you have to override
+ * {@link #wantChildrenToProcessInputInAjaxUpdate()} and return <code>true</code>.
+ *
  * @author eelcohillenius
  */
 public class TimeField extends FormComponentPanel<LocalTime>
@@ -246,6 +251,14 @@ public String getInput()
 		return String.format("%s:%s", hoursField.getInput(), minutesField.getInput());
 	}
 
+	@Override
+	public void processInputOfChildren()
+	{
+		processInputOfChild(hoursField);
+		processInputOfChild(minutesField);
+		processInputOfChild(amOrPmChoice);
+	}
+
 	@Override
 	public void convertInput()
 	{

wicket-extensions/src/main/java/org/apache/wicket/extensions/markup/html/form/palette/Palette.java

@@ -71,7 +71,12 @@
  *    }
  *  }
  * }</pre>
- * 
+ *
+ * <p>
+ * Alternatively you can override {@link #wantChildrenToProcessInputInAjaxUpdate()} and return <code>true</code>, but
+ * this will submit more data than needed: it will include the form data of the choices and selection components too.
+ *
+ * <p>
  * You can add a {@link DefaultTheme} to style this component in a left to right fashion.
  * 
  * @author Igor Vaynberg ( ivaynberg )
@@ -565,6 +570,12 @@ public int getRows()
 		return rows;
 	}
 
+	@Override
+	public void processInputOfChildren()
+	{
+		processInputOfChild(recorderComponent);
+	}
+
 	@Override
 	public void convertInput()
 	{