jakarta.faces.model.FacesDataModel Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.faces.model;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import java.util.Set;
import jakarta.faces.component.UIData;
import jakarta.inject.Qualifier;
/**
*
*
* The presence of this annotation on a class automatically registers the class with the runtime as a {@link DataModel}
* that is capable of wrapping a type indicated by the {@link FacesDataModel#forClass()} attribute.
*
*
* The runtime must maintain a collection of these {@link DataModel}s such that {@link UIData} and other components
* defined by the Jakarta Server Faces specification can query the runtime for a suitable {@link DataModel} wrapper
* (adapter) for the type of their value. This has to be done after all wrappers for specific types such as
* {@link Set} are tried, but before the {@link ScalarDataModel} is selected as the wrapper. See
* {@link UIData#getValue()}.
*
*
* This query must work as follows:
*
*
* For an instance of type Z that is being bound to a UIData component or other component
* defined by the Jakarta Server Faces specification that utilizes DataModel, the query for that type must
* return the most specific DataModel that can wrap Z.
*
*
* This most specific DataModel is defined as the DataModel that is obtained by first sorting the collection in
* which the registered DataModels are stored (for details on this sorting see below) and then
* iterating through the sorted collection from beginning to end and stopping this iteration at the first match where
* for the class ZZ wrapped by the DataModel (as indicated by the {@link FacesDataModel#forClass()}
* attribute) it holds that ZZ.isAssignableFrom(Z). This match is then taken as the most specific
* DataModel.
*
*
* The sorting must be done as follows:
*
*
* Sort on the class wrapped by a DataModel that is stored in the above mentioned collection such that for any 2 classes
* X and Y from this collection, if an object of X is an instanceof
* an object of Y, X appears in the collection before Y. The
* collection's sorting is otherwise arbitrary. In other words, subclasses come before their superclasses.
*
*
* For example:
*
*
* Given class B, class A extends B and class Q, two possible orders are;
*
* {A, B, Q}
* {Q, A, B}
*
*
*
* The only requirement here is that A appears before B, since A is a subclass of
* B.
*
*
* The specification does not define a public method to obtain an instance of the "most specific DataModel for a given
* type". Such an instance can be obtained using code similar to the following.
*
*
*
*
* @SuppressWarnings("unchecked")
* public <T> DataModel<T> createDataModel(Class<T> forClass, Object value) {
* class LocalUIData extends UIData {
* @Override
* public DataModel<?> getDataModel() {
* return super.getDataModel();
* }
* }
* LocalUIData localUIData = new LocalUIData();
* localUIData.setValue(value);
*
* return (DataModel<T>) localUIData.getDataModel();
* }
*
*
*
*
* For example:
*
*
*
*
* public class Child1 {
*
* }
*
*
*
* and
*
*
*
* package test.faces23;
*
* @FacesDataModel(forClass = Child1.class)
* public class Child1Model<E> extends DataModel<E> {
*
* @Override
* public int getRowCount() {
* return 0;
* }
*
* @Override
* public E getRowData() {
* return null;
* }
*
* @Override
* public int getRowIndex() {
* return 0;
* }
*
* @Override
* public Object getWrappedData() {
* return null;
* }
*
* @Override
* public boolean isRowAvailable() {
* return false;
* }
*
* @Override
* public void setRowIndex(int arg0) {
*
* }
*
* @Override
* public void setWrappedData(Object arg0) {
*
* }
* }
*
*
*
*
* Then the following must work:
*
*
*
*
* DataModel<Child1> myModel = createDataModel(Child1.class, new Child1());
* assert myModel instanceof Child1Model;
* System.out.println(myModel.getClass());
*
*
*
*
* The result printed should be e.g.: "class
* test.faces23.Child1Model"
*
*
*
*
*/
@Retention(RUNTIME)
@Target(TYPE)
@Inherited
@Qualifier
public @interface FacesDataModel {
/**
*
* The value of this annotation attribute is taken to be the type that the DataModel that is annotated with this
* annotation is able to wrap.
*
*
* @return the type that the DataModel that is annotated with this annotation is able to wrap
*/
Class forClass() default Object.class;
}