Versions Compared

Old Version 31

changes.mady.by.user Thies Arntzen

Saved on

compared with

New Version Current

changes.mady.by.user Stijn Geukens

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.
Comment: Migrated to Confluence 5.3

...

  • Wicket provides IModel implementations you can use with any component. These models can do things such as retrieve the value from a resource file, or read and write the value from a Java Bean property.
  • Wicket also provides IModel implementations that defer retrieving the value until it is actually needed, and remove it from the servlet Session when the request is complete. This reduces session memory consumption , and it is particularly useful with large values such as lists.
  • Unlike Swing, you do not have to implement an extra interface or helper class for each different component. Especially for the most often used components such as Labels and TextFields you can easily bind to a bean property.
  • In many cases you can provide the required value directly to the component and it will wrap a default model implementation around it for you.
  • And while you do not have to use beans as your models as you must with Struts, you may still easily use beans if you wish. Wicket provides the appropriate model implementations.

...

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

Annotation processors

There are a number of annotation processors that generate a meta data that can be used to build safe property models. Examples of such processors:

LambdaJ

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);
  }
}