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changes.mady.by.user Thies Arntzen

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Comment: Added example of refactor safe property model.

...

Panel

The IModel interface was simplified in Wicket 2.0:

Code Block
public interface IModel<T> extends IDetachable
{
  T getObject();
  void setObject(final T object);
}

The get and set methods do not take a component argument anymore. Instead, Wicket 2.0 has specialized model interfaces to do with specific issues like recording the 'owning' component of a model. See IAssignmentAwareModel and IInheritableModel (though you typically don't need to know these interfaces directly).

Another change is that IModel does now support generics. This is especially interesting when authoring custom components where you allow only models (compile time) that produce a certain type. ListView for instance only accepts models that produces instances of java.util.List.

Refactor Safe Property Models

With a little bit of help from the LambdaJ project we can stop using fragile PropertyModels.

Code Block

/* www.starjar.com
 * Copyright (c) 2011 Peter Henderson. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0
 */
package com.starjar.wicket;

import ch.lambdaj.function.argument.Argument;
import ch.lambdaj.function.argument.ArgumentsFactory;
import org.apache.wicket.model.PropertyModel;

public class ModelFactory {

  /**
   * Use with the on() function from Lambdaj to have refactor safe property models.
   *
   * e.g.
   * <pre>
   * import static com.starjar.wicket.ModelFactory.*;
   * import static ch.lambdaj.Lambda.*;
   *
   * Contact contact = getContactFromDB();
   *
   * Label l = new Label("id", model(contact, on(Contact.class).getFirstName()));
   *
   *
   * </pre>
   *
   * OR
   *
   * <pre>
   * import static com.starjar.wicket.ModelFactory.*;
   * import static ch.lambdaj.Lambda.*;
   *
   * ContactLDM contactLDM = new ContactLDM(contactId);
   *
   * Label l = new Label("id", model(contactLDM, on(Contact.class).getFirstName()));
   * </pre>
   *
   * Works as expected for nested objects
   *
   * <pre>
   * Label l = new Label("address", model(contactLDM, on(Contact.class).getAddress().getLine1()));
   * </pre>
   *
   *
   * @param <T> Type of the model value
   * @param value
   * @param proxiedValue
   * @return
   */
  public static <T> PropertyModel<T> model(Object value, T proxiedValue) {
    Argument<T> a = ArgumentsFactory.actualArgument(proxiedValue);
    String invokedPN = a.getInkvokedPropertyName();
    PropertyModel<T> m = new PropertyModel<T>(value, invokedPN);
    return m;
  }
}

Which can then be used

Code Block

import static ch.lambdaj.Lambda.*;
import static com.starjar.wicket.ModelFactory.*;


public class MyPanel extends Panel {
  public MyPanel(String id) {
    Label l = new Label("firstName", model(contact, on(Contact.class).getFirstName());
    add(l);
    Label addr = new Label("address", model(contact, on(Contact.class).getAddress().getLine1());
    add(addr);
  }
}