Markup inheritance

Table of contents

Definition
Using Markup Inheritance with Header Contribution

Definition

Wicket provides quite a few ways to modularize your web page creation. In addition to Markup Inheritance, you should also have a look at how you can simplify page creation using Wicket tags and Fragments. Markup Inheritance lets a Component extend the markup of its super class. The subclass markup is inserted at one point in the super class markup.

Let's see an example:

Parent.java:

public class Parent extends Component {}

Parent.html:

... parent content ...
      <wicket:child/>
   ... parent content ...

Child.html

<wicket:extend>
      ... child content ...
   </wicket:extend>

Child.java:

public class Child extends Parent {}

Renders as:

... parent content ...
      ... child content ...
   ... parent content ...

It is just like having a Panel defined in your Component class markup, and let subclasses add the Panel. But it doesn't need an extra Component and is much easier to use. Markup Inheritance is also a convenient replacement for most Border components.

Markup Inheritance works with WebPages, so you can easily use the same header and footer on several pages.

Using Markup Inheritance with Header Contribution

You can now combine Markup Inheritance with Header Contribution. First, define a base Page. The markup:

<html>
  <head>
  </head>
  <body>
    Base Page Before
    <wicket:child/>
    Base Page After
  </body>
</html>

The Java code:

class Parent extends WebPage
{
  public Parent()
  {
  }
}

Next define a child Page. First the markup:

<head>
  <span wicket:id="label"/>
</head>
<wicket:extend>
  Child Page
</wicket:extend>

The Java code:

public class Child extends Parent
{
  public Child()
  {
     add(new Label("label", "Here you go"));
  }
}

Now, when you fire this all out the resulting page should render as:

<html>
  <head>
    <span wicket:id="label">Here you go</span>
  </head>
  <body>
    Base Page Before
    Child Page
    Base Page After
  </body>
</html>

Markup Inheritance with Wicket 1.1 on Phil's Weblog

TODO: describe <wicket:head> its functionality and the difference to <head>

<head> will be inserted in output automatically if required
<head> is not a wicket specific tag and you must use add() for components within in <head>
<head> is supported by panels, borders and inherited markup, but is not copied to the output. They are for previewability only (except on Pages)
<wicket:head> is not necessary in Page markup. Wicket interprets <head> as <wicket:head> automatically.
<wicket:head> makes sense in Panels, Borders and inherited markup (of Panels, Borders and Pages)
components within <wicket:head> must be added by means of add() like allways with Wicket. No difference (anymore)
<wicket:head> and it's content is copied into the output. Component contained in <wicket.head> are rendered as usual