org.springframework.web.servlet.tags.form.SelectedValueComparator Maven / Gradle / Ivy
/*
* Copyright 2002-2007 the original author or authors.
*
* 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.
*/
package org.springframework.web.servlet.tags.form;
import java.beans.PropertyEditor;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import org.springframework.beans.PropertyEditorRegistry;
import org.springframework.core.enums.LabeledEnum;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.servlet.support.BindStatus;
/**
* Utility class for testing whether a candidate value matches a {@link BindStatus#getValue data bound value}.
* Eagerly attempts to prove a comparison through a number of avenues to deal with issues such as instance
* inequality, logical (String-representation-based) equality and {@link PropertyEditor}-based comparison.
*
* Full support is provided for comparing arrays, {@link Collection Collections} and {@link Map Maps}.
*
*
Equality Contract
* For single-valued objects equality is first tested using standard {@link Object#equals Java equality}. As
* such, user code should endeavour to implement {@link Object#equals} to speed up the comparison process. If
* {@link Object#equals} returns false then an attempt is made at an
* {@link #exhaustiveCompare exhaustive comparison} with the aim being to prove equality rather
* than disprove it.
*
* Special support is given for instances of {@link LabeledEnum} with a String-based
* comparison of the candidate value against the code of the {@link LabeledEnum}. This can be useful when a
* {@link LabeledEnum} is used to define a list of '<option>' elements in HTML.
*
*
Next, an attempt is made to compare the String representations of both the candidate and bound
* values. This may result in true in a number of cases due to the fact both values will be represented
* as Strings when shown to the user.
*
*
Next, if the candidate value is a String, an attempt is made to compare the bound value to
* result of applying the corresponding {@link PropertyEditor} to the candidate. This comparison may be
* executed twice, once against the direct String instances, and then against the String
* representations if the first comparison results in false.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
abstract class SelectedValueComparator {
/**
* Returns true if the supplied candidate value is equal to the value bound to
* the supplied {@link BindStatus}. Equality in this case differs from standard Java equality and
* is described in more detail here.
*/
public static boolean isSelected(BindStatus bindStatus, Object candidateValue) {
Object boundValue = getBoundValue(bindStatus);
if (boundValue == null) {
return (candidateValue == null);
}
boolean selected = false;
if (boundValue.getClass().isArray()) {
selected = collectionCompare(CollectionUtils.arrayToList(boundValue), candidateValue, bindStatus);
}
else if (boundValue instanceof Collection) {
selected = collectionCompare((Collection) boundValue, candidateValue, bindStatus);
}
else if (boundValue instanceof Map) {
selected = mapCompare((Map) boundValue, candidateValue, bindStatus);
}
if (!selected) {
if (ObjectUtils.nullSafeEquals(boundValue, candidateValue)) {
selected = true;
}
else {
selected = exhaustiveCompare(boundValue, candidateValue, bindStatus.getEditor());
}
}
return selected;
}
private static boolean mapCompare(Map boundMap, Object candidateValue, BindStatus bindStatus) {
if (boundMap.containsKey(candidateValue)) {
return true;
}
else {
return exhaustiveCollectionCompare(boundMap.keySet(), candidateValue, bindStatus);
}
}
private static boolean collectionCompare(Collection boundCollection, Object candidateValue, BindStatus bindStatus) {
if (boundCollection.contains(candidateValue)) {
return true;
}
else {
return exhaustiveCollectionCompare(boundCollection, candidateValue, bindStatus);
}
}
private static Object getBoundValue(BindStatus bindStatus) {
if (bindStatus == null) {
return null;
}
if (bindStatus.getEditor() != null) {
Object editorValue = bindStatus.getEditor().getValue();
if (editorValue != null) {
return editorValue;
}
}
return bindStatus.getValue();
}
private static boolean exhaustiveCollectionCompare(
Collection collection, Object candidateValue, BindStatus bindStatus) {
PropertyEditorRegistry editorRegistry = null;
if (bindStatus.getErrors() instanceof BindingResult) {
editorRegistry = ((BindingResult) bindStatus.getErrors()).getPropertyEditorRegistry();
}
for (Iterator it = collection.iterator(); it.hasNext();) {
Object element = it.next();
PropertyEditor propertyEditor = null;
if (element != null && editorRegistry != null) {
propertyEditor = editorRegistry.findCustomEditor(element.getClass(), bindStatus.getPath());
}
if (exhaustiveCompare(element, candidateValue, propertyEditor)) {
return true;
}
}
return false;
}
private static boolean exhaustiveCompare(Object boundValue, Object candidate, PropertyEditor propertyEditor) {
String candidateDisplayString = ObjectUtils.getDisplayString(candidate);
if (boundValue instanceof LabeledEnum) {
LabeledEnum labeledEnum = (LabeledEnum) boundValue;
String enumCodeAsString = ObjectUtils.getDisplayString(labeledEnum.getCode());
if (enumCodeAsString.equals(candidateDisplayString)) {
return true;
}
String enumLabelAsString = ObjectUtils.getDisplayString(labeledEnum.getLabel());
if (enumLabelAsString.equals(candidateDisplayString)) {
return true;
}
}
else if (ObjectUtils.getDisplayString(boundValue).equals(candidateDisplayString)) {
return true;
}
else if (propertyEditor != null && candidate instanceof String) {
// Try PE-based comparison (PE should *not* be allowed to escape creating thread)
Object originalValue = propertyEditor.getValue();
String candidateAsString = (String) candidate;
try {
propertyEditor.setAsText(candidateAsString);
if (ObjectUtils.nullSafeEquals(boundValue, propertyEditor.getValue())) {
return true;
}
}
finally {
propertyEditor.setValue(originalValue);
}
if (propertyEditor.getValue() != null) {
return ObjectUtils.nullSafeEquals(candidateAsString, propertyEditor.getAsText());
}
}
return false;
}
}