org.magicwerk.brownies.html.IdMap Maven / Gradle / Ivy
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package org.magicwerk.brownies.html;
import java.util.Map;
import java.util.WeakHashMap;
import org.magicwerk.brownies.core.CheckTools;
import org.magicwerk.brownies.core.TypeTools;
/**
* Class {@link IdMap} allows to construct unique ids which can be used as id attribute for HTML elements.
*/
public class IdMap {
/** Map holding the ids for the objects. It is implemented as {@link WeakHashMap} to prevent memory issues. */
Map ids = new WeakHashMap<>();
/**
* Clear map. As the map is implemented as {@link WeakHashMap}, it should normally not be necessary to clean it manually.
*/
public void clear() {
ids.clear();
}
/**
* Returns id for passed key. If the key already has an id, it is returned. Otherwise a new id is created and returned.
*/
public String get(Object key) {
return ids.computeIfAbsent(key, k -> createId());
}
/**
* Creates a new id for the passed key and and returns it. If the key already has an id, an exception is thrown.
*/
public String addAbsent(Object key) {
String id = createId();
String oldId = ids.putIfAbsent(key, id);
CheckTools.check(oldId == null, "Duplicate key: {}", key);
return id;
}
/**
* Retrieves the existing id for the passed key and and returns it. If the key does not have an id, an exception is thrown.
*/
public String getPresent(Object key) {
String id = ids.get(key);
CheckTools.check(id != null, "Unknown key: {}", key);
return id;
}
String createId() {
return TypeTools.format(ids.size());
}
}