This framework makes use of the meta-data contributed by the Design-time Meta-data Framework. It's intention in this release is to simplify how services like Content Assist and Validation can be provided in source editors for tag library based attributes values.
The goal for this framework is to allow developers to assign "runtime type" information to an attibute's value using meta-data and then, because based on that type, "features" can naturally be exposed.
To make this more concrete, let's consider the example of the JSF Core actionListener
tag and its type
attribute. The value should resolve to a Java class type that implements the interface javax.faces.event.ActionListener
. Having this knowledge is enough to provide:
In the above example, the "Type" is a Java class type and we have identified three "Feature" that the type implements.
We have created an interface called ITypeDescriptor
that represents the runtime type of the attribute value of a tag. An implementor needs to return a list of feature adapters that this type supports. The features must implement the IMetaDataEnabledFeature
interface.
A default implementation, AbstractRootTypeDescriptor
has been provided as a convenient starting point for implementing types, and it itself implements AbstractMetaDataEnabledFeature
. This allows the type descriptor to implement features itself which should simplify development.
We bind a type identifier in meta-data to a class through an extension point. org.eclipse.jst.jsf.core.AttributeValueRuntimeTypes
. Please see Design-time Meta-Data Framework to see how the meta-data files are created.
The JSF Tools project has implemented a type descriptor class org.eclipse.jst.jsf.core.attributevalues.JavaClassType
. In order to use this type, it must first be declared as an AttributeValueRuntimeType
and then referenced in a meta-data file.
Below comes from the org.eclipse.jst.jsf.core
plugin that declares this type:
<attributeValueRuntimeType class="org.eclipse.jst.jsf.core.attributevalues.JavaClassType" id="attributevalues.JavaClassType"/>
Below is the section of the jsf_core.xml meta-data file from the core plugin that supplies meta-data for the actionListener
tag:
<entity id="actionListener"> <entity id="type"> <trait id="attribute-value-runtime-type"> <value> org.eclipse.jst.jsf.core.attributevalues.JavaClassType </value> </trait> <trait id="valid-interfaces"> <value>javax.faces.event.ActionListener</value> </trait> </entity> </entity>
Notice that the value of the attribute-value-runtime-type
trait uses the plugin qualified id of the AttributeValueRuntimeType extension.
For a complete list of implemented types and features, please see the API reference
The JavaClassType
implements two Features:
Although not applicable to the JavaClassType
, the following round out the Features defined by this release:
The Feature implementer can require additional information from meta-data. Notice that the JavaClassType
calls back to the meta-data to get the list of valid-interface
values. For a complete list of the property names used by the Types and Features from the core plugin see the constant values reference page
A client interested in requesting a set of all the Feature implementers for a given tag attribute will use the MetaDataEnabledProcessingFactory
and the getAttributeValueRuntimeTypeFeatureProcessors method
.
This method will lookup the runtime type from the meta-data file that it will identify from the passed context.
This method is currently being called by the JSPSemanticValidator
with IValidValues.class
and IValidELValues.class
passed as the feature class along with the context. For content assist, IPossibleValues.class
is being passed by the content assist processor.
Hopefully by now you know enough knowledge to create your own types, or reuse existing types in your meta-data files. But what if you wanted to associate a completely new behaviour(Feature) with a runtime type? This is handled by implementing a new IMetaDataEnabledFeature
and registering it against a type identifier.
To register, use the org.eclipse.jst.jsf.metadataprocessing.MetaDataEnabledFeatures
extension-point.