私は次の問題を抱えています：
ドロップダウンに要素をアルファベット順に並べ替えて表示させるためのエレガントで再利用可能なソリューションはありますか？
最終的には、render を使用するのがおそらく最善の方法だと思います。再利用可能で効率的にするために、これをビヘイビアに分離しました。
コードは次のとおりです。
import org.apache.wicket.Component;
import org.apache.wicket.behavior.Behavior;
import org.apache.wicket.markup.html.form.AbstractChoice;
import org.apache.wicket.markup.html.form.IChoiceRenderer;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import static java.util.Arrays.sort;
/**
* This {@link Behavior} can only be used on {@link AbstractChoice} subclasses. It will sort the choices
* according to their "natural display order" (i.e. the natural order of the display values of the choices).
* This assumes that the display value implements {@link Comparable}. If this is not the case, you should
* provide a comparator for the display value. An instance of this class <em>cannot be shared</em> between components.
* Because the rendering can be costly, the sort-computation is done only once, by default,
* unless you set to <code>false</code> the <code>sortOnlyOnce</code> argument in the constructor.
*
* @author donckels (created on 2012-06-07)
*/
@SuppressWarnings({"unchecked"})
public class OrderedChoiceBehavior extends Behavior {
// ----- instance fields -----
private Comparator displayValueComparator;
private boolean sortOnlyOnce = true;
private boolean sorted;
// ----- constructors -----
public OrderedChoiceBehavior() {
}
public OrderedChoiceBehavior(boolean sortOnlyOnce) {
this.sortOnlyOnce = sortOnlyOnce;
}
public OrderedChoiceBehavior(boolean sortOnlyOnce, Comparator displayValueComparator) {
this.sortOnlyOnce = sortOnlyOnce;
this.displayValueComparator = displayValueComparator;
}
// ----- public methods -----
@Override
public void beforeRender(Component component) {
if (this.sorted && this.sortOnlyOnce) { return;}
AbstractChoice owner = (AbstractChoice) component;
IChoiceRenderer choiceRenderer = owner.getChoiceRenderer();
List choices = owner.getChoices();
// Temporary data structure: store the actual rendered value with its initial index
Object[][] displayValuesWithIndex = new Object[choices.size()][2];
for (int i = 0, valuesSize = choices.size(); i < valuesSize; i++) {
Object value = choices.get(i);
displayValuesWithIndex[i][0] = choiceRenderer.getDisplayValue(value);
displayValuesWithIndex[i][1] = i;
}
sort(displayValuesWithIndex, new DisplayValueWithIndexComparator());
List valuesCopy = new ArrayList(choices);
for (int i = 0, length = displayValuesWithIndex.length; i < length; i++) {
Object[] displayValueWithIndex = displayValuesWithIndex[i];
int originalIndex = (Integer) displayValueWithIndex[1];
choices.set(i, valuesCopy.get(originalIndex));
}
this.sorted = true;
}
public Comparator getDisplayValueComparator() {
return this.displayValueComparator;
}
// ----- inner classes -----
private class DisplayValueWithIndexComparator implements Comparator<Object[]> {
// ----- Comparator -----
public int compare(Object[] left, Object[] right) {
Object leftDisplayValue = left[0];
Object rightDisplayValue = right[0];
if (null == leftDisplayValue) { return -1;}
if (null == rightDisplayValue) { return 1;}
if (null == getDisplayValueComparator()) {
return ((Comparable) leftDisplayValue).compareTo(rightDisplayValue);
} else {
return getDisplayValueComparator().compare(leftDisplayValue, rightDisplayValue);
}
}
}
}
Java のCollatorを使用して DropDownChoice のこの拡張機能を使用します(基本的にロケールに依存した並べ替え - 国別文字と国別の並べ替え規則を考慮に入れます)。
Wicket 6 および Java 5+ でテストされたコード:
import java.text.Collator;
import java.util.Comparator;
import java.util.List;
import java.util.Locale;
import org.apache.wicket.Session;
import org.apache.wicket.markup.html.form.DropDownChoice;
import org.apache.wicket.markup.html.form.IChoiceRenderer;
import org.apache.wicket.model.IModel;
import com.google.common.collect.Ordering;
/**
* DropDownChoice which sort its choices (or in HTML's terminology select's options) according it's localized value
* and using current locale based Collator so it's sorted how it should be in particular language (ie. including national characters,
* using right order).
*
* @author Michal Bernhard michal@bernhard.cz 2013
*
* @param <T>
*/
public class OrderedDropDownChoice<T> extends DropDownChoice<T> {
public OrderedDropDownChoice(String id, IModel<? extends List<? extends T>> choices, IChoiceRenderer<? super T> renderer) {
super(id, choices, renderer);
}
public OrderedDropDownChoice(String id, IModel<? extends List<? extends T>> choices) {
super(id, choices);
}
public OrderedDropDownChoice(String id) {
super(id);
}
public OrderedDropDownChoice(
String id,
IModel<T> model,
IModel<? extends List<? extends T>> choices,
IChoiceRenderer<? super T> renderer) {
super(id, model, choices, renderer);
}
@Override
public List<? extends T> getChoices() {
List<? extends T> unsortedChoices = super.getChoices();
List<? extends T> sortedChoices = Ordering.from(displayValueAlphabeticComparator()).sortedCopy(unsortedChoices);
return sortedChoices;
}
private Collator localeBasedTertiaryCollator() {
Locale currentLocale = Session.get().getLocale();
Collator collator = Collator.getInstance(currentLocale);
collator.setStrength(Collator.TERTIARY);
return collator;
}
private Comparator<T> displayValueAlphabeticComparator() {
final IChoiceRenderer<? super T> renderer = getChoiceRenderer();
return new Comparator<T>() {
@Override
public int compare(T o1, T o2) {
Object o1DisplayValue = renderer.getDisplayValue(o1);
Object o2DisplayValue = renderer.getDisplayValue(o2);
return localeBasedTertiaryCollator().compare(o1DisplayValue, o2DisplayValue);
}
};
}
}
Wicket ベースのソリューションが必要な場合は、次のような方法でリストを並べ替えることができます。
public class ChoiceRendererComparator<T> implements Comparator<T> {
private final IChoiceRenderer<T> renderer;
public ChoiceRendererComparator(IChoiceRenderer<T> renderer) {
this.renderer = renderer;
}
@SuppressWarnings("unchecked")
public int compare(T o1, T o2) {
return ((Comparable<Object>) renderer.getDisplayValue(o1)).compareTo(renderer.getDisplayValue(o2));
}
}
使用法：
List<Entity> list = ...
IChoiceRenderer<Entity> renderer = ...
Collections.sort(list, new ChoiceRendererComparator<Entity>(renderer));
DropDownChoice<Entity> dropdown = new DropDownChoice<Entity>("dropdown", list, renderer);
私の会社で使用しているソリューションは Javascript ベースで、並べ替えたいドロップダウンに特別な css クラスを設定し、ちょっとした jQuery トリックで並べ替えを行います。
同じ問題に直面して、ローカライズ データの一部を XML からデータベースに移動し、一致するリゾルバーを実装して、ローカライズされた文字列を並べ替えに使用できるようになりました。テーブルの設計と休止状態の構成はややこしくて、ここで説明されています: Hibernate @ElementCollection - Better solution needed .
ResourceLoader は次の行に沿っています。
public class DataBaseStringResourceLoader extends ComponentStringResourceLoader {
private static final transient Logger logger = Logger
.getLogger(DataBaseStringResourceLoader.class);
@Inject
private ISomeDAO someDao;
@Inject
private IOtherDao otherDao;
@Inject
private IThisDAO thisDao;
@Inject
private IThatDAO thatDao;
@Override
public String loadStringResource(Class<?> clazz, String key, Locale locale,
String style, String variation) {
String resource = loadFromDB(key, new Locale(locale.getLanguage()));
if (resource == null) {
resource = super.loadStringResource(clazz, key, locale, style, variation);
}
return resource;
}
private String loadFromDB(String key, Locale locale) {
String resource = null;
if (locale.getLanguage() != Locale.GERMAN.getLanguage()
&& locale.getLanguage() != Locale.ENGLISH.getLanguage()) {
locale = Locale.ENGLISH;
}
if (key.startsWith("some") || key.startsWith("other")
|| key.startsWith("this") || key.startsWith("that")) {
Integer id = Integer.valueOf(key.substring(key.indexOf(".") + 1));
ILocalizedObject master;
if (key.startsWith("some")) {
master = someDao.findById(id);
} else if (key.startsWith("other")) {
master = otherDao.findById(id);
} else if (key.startsWith("this") ){
master = thisDao.findById(id);
} else {
master = thatDao.findById(id);
}
if (master != null && master.getNames().get(locale) != null) {
resource = master.getNames().get(locale).getName();
} else if (master == null) {
logger.debug("For key " + key + " there is no master.");
}
}
return resource;
}
[...]
}