Java tutorial
/*<license> Copyright 2004 - $Date$ by PeopleWare n.v.. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. </license>*/ package org.ppwcode.vernacular.value_III.jsf; import static org.ppwcode.metainfo_I.License.Type.APACHE_V2; import java.beans.PropertyEditor; import java.beans.PropertyEditorManager; import java.util.Locale; import javax.faces.component.UIComponent; import javax.faces.component.UIViewRoot; import javax.faces.context.FacesContext; import javax.faces.convert.ConverterException; import javax.faces.el.EvaluationException; import javax.faces.el.ValueBinding; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.ppwcode.metainfo_I.Copyright; import org.ppwcode.metainfo_I.License; import org.ppwcode.metainfo_I.vcs.SvnInfo; import org.ppwcode.vernacular.value_III.DisplayLocaleBasedEnumerationValueEditor; /** * <p>This implementation of {@link AbstractPropertyEditorConverter} finds * the target type by looking at the <code>component</code> value binding, * and finds a {@link PropertyEditor} by asking the {@link PropertyEditorManager} * one for the target type. This means a converter of this type * works completely automatic if the system can find the * {@link PropertyEditor} type.</p> * <p><strong>It is however still necessary to tell JavaServer Faces about * this converter for each separate type that needs to use it, with an * entry in <kbd>faces-config.xml</kbd>:</strong></p> * <pre> * <converter> * <converter-for-class><var>FqcnOfTargetType</var></converter-for-class> * <converter-class>be.peopleware.jsf_II.convert.AutomaticPropertyEditorConverter</converter-class> * </converter> * </pre> * * @author Jan Dockx * @author PeopleWare n.v. * * @mudo contract and unit tests * @mudo UNFINISHED */ @Copyright("2004 - $Date$, PeopleWare n.v.") @License(APACHE_V2) @SvnInfo(revision = "$Revision$", date = "$Date$") public class AutomaticPropertyEditorConverter extends AbstractPropertyEditorConverter { private static final Log LOG = LogFactory.getLog(AutomaticPropertyEditorConverter.class); /** * A {@link PropertyEditor} for the * {@link ValueBinding#getType(FacesContext) type of the value binding} * is requested from the {@link PropertyEditorManager}. If no such * editor is found, a {@link ConverterException} is thrown. * If the retrieved {@link PropertyEditor} is of type, * {@link DisplayLocaleBasedEnumerationValueEditor}, * the {@link DisplayLocaleBasedEnumerationValueEditor#setDisplayLocale(Locale) display locale} * of the editor is set to the locale of the current {@link UIViewRoot}. * * @basic * @throws ConverterException * PropertyEditorManager.findEditor( * component.getValueBinding("value").getType(context) * ) == null; * No {@link PropertyEditor} found for the type of the value binding * of <code>component</code> */ @Override protected PropertyEditor getPropertyEditor(final FacesContext context, final UIComponent component) throws ConverterException { assert component != null; assert context != null; if ($propertyEditor == null) { LOG.debug("no PropertyEditor in cache; retrieving fresh one"); try { // try to find target type Class<?> targetType = component.getValueBinding("value").getType(context); /* throws EvaluationException < PropertyNotFoundException throws NullPointerException, not for component == null, context == null or "value" == null, but because their might not be a value binding */ if (targetType.isArray()) { LOG.debug("target type " + targetType + " is an array. Converting " + "arrays makes no sense, we probably want to convert elements " + "of the array (and the component is a compound handling " + "component, like selectMany). We'll look for a converter for the " + "component type."); targetType = targetType.getComponentType(); } // try to find a property editor for target type LOG.debug("target type of component value binding \"value\": " + targetType); $propertyEditor = PropertyEditorManager.findEditor(targetType); if ($propertyEditor == null) { // still LOG.debug("no PropertyEditor found for type \"" + targetType + "\""); throw new ConverterException("Could not locate a PropertyEditor for type " + targetType); } else { LOG.debug("PropertyEditor found: " + $propertyEditor); if ($propertyEditor instanceof DisplayLocaleBasedEnumerationValueEditor) { assert $propertyEditor != null; Locale displayLocale = context.getViewRoot().getLocale(); LOG.debug("PropertyEditor is of type DisplayLocaleBasedEnumerationValueEditor; " + "setting display locale to " + displayLocale); ((DisplayLocaleBasedEnumerationValueEditor<?>) $propertyEditor) .setDisplayLocale(displayLocale); } } } catch (NullPointerException npExc) { new ConverterException( "Could not retrieve target type from component, " + "because there is no value binding"); } catch (EvaluationException eExc) { // and PropertyNotFoundException new ConverterException("Could not retrieve target type from component", eExc); } } LOG.debug("returning PropertyEditor: " + $propertyEditor); return $propertyEditor; } private PropertyEditor $propertyEditor; }