Richard Wilkinson’s Blog

Wicket Component Expressions

While writing some unit tests for a wicket application I was working on, I found that I was writing a lot of component path expressions to get at various components in my pages.
However after some refactoring of the page hierarchy I had to re-write most of the expressions to take make the tests work again.

This lead me to think that maybe there could be an easier way for getting at components, using * to represent any child component at a given level, and ** to represent any child component at any level.

Doing this would mean that you could re-write this:

“panel1:innerpanel1:form1:textfield1”

as

“*:*:form1:textfield1”

or

“**:form:textfield1”

or even

“**:textfield1”

Then I got thinking that I would be pretty simple to place type restrictions on the results, so you could set the following expression:

“**” and type restriction of TextField

to get all TextField component on the page or

“panel1:**” and type restriction of ListView

to get all ListView components which are children of the panel1 component.

To use component expressions I created 4 static methods

• public static Component findComponent(Component parent,
   String expression)

• public static Component findComponent(Component parent,
   String expression,Class<? extends Component>typeRestriction)

• public static List findAllComponents(Component parent,
   String expression)

• public static List findAllComponents(Component parent,
   String expression, Class<? extends Component> typeRestriction)

The code is checked into the london wicket google code repository, and you can include it as a dependency to your project by adding the following to your pom.xml

<repositories>
	<repository>
		<id>londonwicket</id>
		<url>http://londonwicket.googlecode.com/svn/repo</url>
		<releases>
			<enabled>true</enabled>
		</releases>
		<snapshots>
			<enabled>true</enabled>
		</snapshots>
	</repository>
</repositories>

<dependency>
	<groupId>com.googlecode.londonwicket</groupId>
	<artifactId>wicket-component-expressions</artifactId>
	<version>0.1.0</version>
</dependency>

There are tests to cover all the different cases I could think of. Any comments, bug fixes, or improvements would be more than welcome.