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 javax.faces.component.UIComponent; import javax.faces.context.FacesContext; import javax.faces.convert.Converter; import javax.faces.convert.ConverterException; 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.toryt.annotations_I.Expression; import org.toryt.annotations_I.Invars; /** * <p>Support for converters based on {@link PropertyEditor PropertyEditors}. * Derive from this class and implement {@link #getPropertyEditor(FacesContext, UIComponent)}. * Then add an entry in <kbd>faces-config.xml</kbd> to map the target types to the correct converter class * descendant.</p> * <p>Often, there are 2 String representations of value objects:</p> * <ul> * <li>a programmatic representation, e.g., to be used as values in a HTML * select option tag; and</li> * <li>a label, or display name, to be presented to end users.</li> * </ul> * <p>When {@link #isLabelRepresentation()} is <code>true</code>, this convertor's * {@link #getAsString(FacesContext, UIComponent, Object)} method returns the label. If * {@link #isLabelRepresentation()} is <code>false</code> (the default), the * {@link #getAsString(FacesContext, UIComponent, Object)} method returns the programmatic representation. * This only works if the property editor found for the type of the value to be converted</p> * <p><strong>Note that the {@link #getAsObject(FacesContext, UIComponent, String)} * method only works when {@link #isLabelRepresentation()} is <code>false</code>: * it is often impossible to convert a human-readable label to an * object.</strong></p> * * @author Wim Lambrechts * @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 = "$Date$") @Invars(@Expression("propertyEditor != null")) public abstract class AbstractPropertyEditorConverter implements Converter { private static final Log LOG = LogFactory.getLog(AbstractPropertyEditorConverter.class); /** * Default constructor. */ protected AbstractPropertyEditorConverter() { LOG.debug("creation of new ...PropertyEditorConverter (" + getClass().getName() + ")"); } /** * @pre context != null; * @pre component != null; * @return ; the result of the conversion of <code>value</code> * to an Object by {@link #getPropertyEditor(FacesContext, UIComponent)} * @throws ConverterException * getPropertyEditor(context, component); * @throws ConverterException * getPropertyEditor(context, component).getValue()#IllegalArgumentException; * @throws ConverterException * isLabelRepresenation(); */ public final Object getAsObject(final FacesContext context, final UIComponent component, final String value) throws ConverterException { assert context != null; assert component != null; LOG.debug("request to convert \"" + value + "\" to object for " + component + "(id = " + component.getClientId(context) + ")"); if (isLabelRepresentation()) { LOG.debug("Cannot convert from String to Object in label-representation-mode"); throw new ConverterException("Cannot convert from String to Object in " + "label-representation-mode"); } try { PropertyEditor editor = getPropertyEditor(context, component); // ConverterException LOG.debug("retrieved PropertyEditor: " + editor); editor.setAsText(value); Object result = editor.getValue(); if (LOG.isDebugEnabled()) { LOG.debug("convertion result: " + result); } return result; } catch (IllegalArgumentException iae) { // MUDO (jand) good FacesMessage, i18n; find out what happens if this fails throw new ConverterException(iae); } } /** * @pre context != null; * @pre component != null; * @return ; the result of the conversion of <code>value</code> * to a String by {@link #getPropertyEditor(FacesContext, UIComponent)} * @throws ConverterException * getPropertyEditor(context, component); */ public final String getAsString(final FacesContext context, final UIComponent component, final Object value) throws ConverterException { assert context != null; assert component != null; if (LOG.isDebugEnabled()) { LOG.debug("request to convert object \"" + value + "\" to String for " + component + "(id = " + component.getClientId(context) + ")"); } PropertyEditor editor = getPropertyEditor(context, component); // ConverterException LOG.debug("retrieved PropertyEditor: " + editor); editor.setValue(value); String result = editor.getAsText(); LOG.debug("convertion result: " + result); return result; } /** * @basic * @init false; */ public final boolean isLabelRepresentation() { return $labelRepresentation; } /** * @post new.isLabelRepresentation() == labelRepresentation; */ public final void setLabelRepresentation(final boolean labelRepresentation) { $labelRepresentation = labelRepresentation; } private boolean $labelRepresentation; /** * Subclasses need to implement this method. Return a {@link PropertyEditor} * for the target type of this converter. This method is not allowed to * return <code>null</code>. * * @pre context != null; * @pre component != null; * @basic * @throws ConverterException * true; */ protected abstract PropertyEditor getPropertyEditor(final FacesContext context, final UIComponent component) throws ConverterException; }