org.apache.wicket.ClassAttributeModifier.java Source code

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Here is the source code for org.apache.wicket.ClassAttributeModifier.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket;

import java.io.Serializable;
import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;
import java.util.regex.Pattern;

import org.apache.wicket.behavior.AttributeAppender;
import org.apache.wicket.util.string.Strings;

/**
 * An AttributeModifier specialized in managing the <em>CSS class</em>
 * attribute
 */
public abstract class ClassAttributeModifier extends AttributeAppender {
    private static final Pattern SPLITTER = Pattern.compile("\\s+");

    /**
     * Constructor.
     */
    public ClassAttributeModifier() {
        super("class", null, " ");
    }

    @Override
    protected Serializable newValue(String currentValue, String appendValue) {
        String[] classes;
        if (Strings.isEmpty(currentValue)) {
            classes = new String[0];
        } else {
            classes = SPLITTER.split(currentValue.trim());
        }
        Set<String> oldClasses = new TreeSet<>();
        Collections.addAll(oldClasses, classes);

        Set<String> newClasses = update(oldClasses);

        String separator = getSeparator();
        StringBuilder result = new StringBuilder();
        for (String cls : newClasses) {
            if (result.length() > 0) {
                result.append(separator);
            }
            result.append(cls);
        }
        return result.length() > 0 ? result.toString() : VALUELESS_ATTRIBUTE_REMOVE;
    }

    /**
     * Callback to update the CSS class values for a tag.
     *
     * @param oldClasses
     *          A set with the old class values
     * @return A set with the new class values
     */
    protected abstract Set<String> update(Set<String> oldClasses);
}