org.apache.wicket
Class AttributeModifier

java.lang.Object
  org.apache.wicket.behavior.Behavior
      org.apache.wicket.AttributeModifier

All Implemented Interfaces:

Serializable, IEventSink, IClusterable, IHeaderContributor

Direct Known Subclasses:

AttributeAppender

public class AttributeModifier
extends Behavior
implements IClusterable

This class allows a tag attribute of a component to be modified dynamically with a value obtained from a model object. This concept can be used to programmatically alter the attributes of components, overriding the values specified in the markup. The two primary uses of this class are to allow overriding of markup attributes based on business logic and to support dynamic localization. The replacement occurs as the component tag is rendered to the response.

The attribute whose value is to be modified must be given on construction of the instance of this class along with the model containing the value to replace with. Optionally a pattern can be supplied that is a regular expression that the existing value must match before the replacement can be carried out.

If an attribute is not in the markup, this modifier will add an attribute to the tag only if addAttributeIfNotPresent is true and the replacement value is not null.

Instances of this class should be added to components via the Component.add(org.apache.wicket.behavior.Behavior...) } method after the component has been constructed.

It is possible to create new subclasses of AttributeModifier by overriding the newValue(String, String) method. For example, you could create an AttributeModifier subclass which appends the replacement value like this: new AttributeModifier("myAttribute", model) { protected String newValue(final String currentValue, final String replacementValue) { return currentValue + replacementValue; } };

Author:

Chris Turner, Eelco Hillenius, Jonathan Locke, Martijn Dashorst, Ralf Ebert

See Also:

Serialized Form

Field Summary

static String	VALUELESS_ATTRIBUTE_ADD Marker value to have an attribute without a value added.
static String	VALUELESS_ATTRIBUTE_REMOVE Marker value to have an attribute without a value removed.

Constructor Summary

AttributeModifier(String attribute, boolean addAttributeIfNotPresent, IModel<?> replaceModel)
Create a new attribute modifier with the given attribute name and model to replace with.

AttributeModifier(String attribute, IModel<?> replaceModel)
Create a new attribute modifier with the given attribute name and model to replace with.

AttributeModifier(String attribute, String pattern, boolean addAttributeIfNotPresent, IModel<?> replaceModel)
Create a new attribute modifier with the given attribute name and expected pattern to match plus the model to replace with.

AttributeModifier(String attribute, String pattern, IModel<?> replaceModel)
Create a new attribute modifier with the given attribute name and expected pattern to match plus the model to replace with.

Method Summary

void	detach(Component component) Detach the model if it was a IDetachableModel Internal method.
boolean	getAddAttributeIfNotPresent()
String	getAttribute()
String	getPattern()
protected IModel<?>	getReplaceModel() Gets the replacement model.
boolean	isEnabled(Component component) Called when a components is rendering and wants to render this behavior.
protected String	newValue(String currentValue, String replacementValue) Gets the value that should replace the current attribute value.
void	onComponentTag(Component component, ComponentTag tag) Called any time a component that has this behavior registered is rendering the component tag.
void	replaceAttributeValue(Component component, ComponentTag tag) Checks the given component tag for an instance of the attribute to modify and if all criteria are met then replace the value of this attribute with the value of the contained model object.
void	setEnabled(boolean enabled) Sets whether this attribute modifier is enabled or not.
String	toString()

Methods inherited from class org.apache.wicket.behavior.Behavior

afterRender, beforeRender, bind, canCallListenerInterface, getStatelessHint, isTemporary, onConfigure, onEvent, onException, renderHead, unbind

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

VALUELESS_ATTRIBUTE_ADD

public static final String VALUELESS_ATTRIBUTE_ADD

Marker value to have an attribute without a value added.

See Also:

Constant Field Values

VALUELESS_ATTRIBUTE_REMOVE

public static final String VALUELESS_ATTRIBUTE_REMOVE

Marker value to have an attribute without a value removed.

See Also:

Constant Field Values

Constructor Detail

AttributeModifier

public AttributeModifier(String attribute,
                         boolean addAttributeIfNotPresent,
                         IModel<?> replaceModel)

Create a new attribute modifier with the given attribute name and model to replace with. The additional boolean flag specifies whether to add the attribute if it is not present.

Parameters:

attribute - The attribute name to replace the value for

addAttributeIfNotPresent - Whether to add the attribute if it is not present

replaceModel - The model to replace the value with

AttributeModifier

public AttributeModifier(String attribute,
                         IModel<?> replaceModel)

Create a new attribute modifier with the given attribute name and model to replace with. The attribute will not be added if it is not present.

Parameters:

attribute - The attribute name to replace the value for

replaceModel - The model to replace the value with

AttributeModifier

public AttributeModifier(String attribute,
                         String pattern,
                         boolean addAttributeIfNotPresent,
                         IModel<?> replaceModel)

Create a new attribute modifier with the given attribute name and expected pattern to match plus the model to replace with. A null pattern will match the attribute regardless of its value. The additional boolean flag specifies whether to add the attribute if it is not present.

Parameters:

attribute - The attribute name to replace the value for

pattern - The pattern of the current attribute value to match

addAttributeIfNotPresent - Whether to add the attribute if it is not present and the replacement value is not null

replaceModel - The model to replace the value with

AttributeModifier

public AttributeModifier(String attribute,
                         String pattern,
                         IModel<?> replaceModel)

Create a new attribute modifier with the given attribute name and expected pattern to match plus the model to replace with. A null pattern will match the attribute regardless of its value. The attribute will not be added if it is not present.

Parameters:

attribute - The attribute name to replace the value for

pattern - The pattern of the current attribute value to match

replaceModel - The model to replace the value with

Method Detail

detach

public final void detach(Component component)

Detach the model if it was a IDetachableModel Internal method. shouldn't be called from the outside. If the attribute modifier is shared, the detach method will be called multiple times.

Overrides:

detach in class Behavior

Parameters:

component - the model that initiates the detachment

getAddAttributeIfNotPresent

public final boolean getAddAttributeIfNotPresent()

Returns:

whether to add the attribute if it is not an attribute in the markup

getAttribute

public final String getAttribute()

Returns:

the attribute name to replace the value for

getPattern

public final String getPattern()

Returns:

the pattern of the current attribute value to match

isEnabled

public boolean isEnabled(Component component)

Description copied from class: Behavior

Called when a components is rendering and wants to render this behavior. If false is returned this behavior will be ignored.

Overrides:

isEnabled in class Behavior

Parameters:

component - the component that has this behavior coupled

Returns:

true if this behavior must be executed/rendered

onComponentTag

public final void onComponentTag(Component component,
                                 ComponentTag tag)

Description copied from class: Behavior

Called any time a component that has this behavior registered is rendering the component tag.

Overrides:

onComponentTag in class Behavior

Parameters:

component - the component that renders this tag currently

tag - the tag that is rendered

replaceAttributeValue

public final void replaceAttributeValue(Component component,
                                        ComponentTag tag)

Checks the given component tag for an instance of the attribute to modify and if all criteria are met then replace the value of this attribute with the value of the contained model object.

Parameters:

component - The component

tag - The tag to replace the attribute value for

setEnabled

public final void setEnabled(boolean enabled)

Sets whether this attribute modifier is enabled or not.

Parameters:

enabled - Whether enabled or not

toString

public String toString()

Overrides:

toString in class Object

See Also:

Object.toString()

getReplaceModel

protected final IModel<?> getReplaceModel()

Gets the replacement model. Allows subclasses access to replace model.

Returns:

the replace model of this attribute modifier

newValue

protected String newValue(String currentValue,
                          String replacementValue)

Gets the value that should replace the current attribute value. This gives users the ultimate means to customize what will be used as the attribute value. For instance, you might decide to append the replacement value to the current instead of just replacing it as is Wicket's default.

Parameters:

currentValue - The current attribute value. This value might be null!

replacementValue - The replacement value. This value might be null!

Returns:

The value that should replace the current attribute value