org.apache.wicket.behavior.AttributeAppender.java Source code

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Here is the source code for org.apache.wicket.behavior.AttributeAppender.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.behavior;

import java.io.Serializable;

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.model.IModel;
import org.apache.wicket.util.string.Strings;

/**
 * AttributeModifier that appends the given value, rather than replace it. This is especially useful
 * for adding CSS classes to markup elements, or adding JavaScript snippets to existing element
 * handlers.
 * 
 * <pre>
 *     &lt;a href=&quot;#&quot; wicket:id=&quot;foo&quot; class=&quot;link&quot; onmouseover=&quot;doSomething()&quot;&gt;
 * </pre>
 * 
 * can be modified with these AttributeAppenders:
 * 
 * <pre>
 * link.add(new AttributeAppender(&quot;class&quot;, Model.of(&quot;hot&quot;)));
 * link.add(new AttributeAppender(&quot;onmouseover&quot;, Model.of(&quot;foo();return false;&quot;)).setSeparator(&quot;;&quot;));
 * </pre>
 * 
 * this will result in the following markup:
 * 
 * <pre>
 *     &lt;a href=&quot;#&quot; wicket:id=&quot;foo&quot; class=&quot;link hot&quot; onmouseover=&quot;doSomething();foo();return false;&quot;&gt;
 * </pre>
 * 
 * @see AttributeModifier#append(String, IModel)
 * @see AttributeModifier#append(String, Serializable)
 * @see AttributeModifier#prepend(String, IModel)
 * @see AttributeModifier#prepend(String, Serializable)
 * 
 * @author Martijn Dashorst
 */
public class AttributeAppender extends AttributeModifier {
    private static final long serialVersionUID = 1L;

    /**
     * Separator between the current value and the concatenated value, typically a space ' ' or
     * colon ';'.
     */
    private String separator;

    /**
     * Creates an attribute modifier that concatenates the {@code replaceModel} to the attribute's
     * current value, optionally separated by the {@link #getSeparator() separator}.
     * 
     * @param attribute
     * @param replaceModel
     */
    public AttributeAppender(String attribute, IModel<?> replaceModel) {
        super(attribute, replaceModel);
    }

    /**
     * Creates an attribute modifier that appends the {@code value} to the attribute's current
     * value, optionally separated by the {@link #getSeparator() separator}.
     * 
     * @param attribute
     * @param value
     */
    public AttributeAppender(String attribute, Serializable value) {
        super(attribute, value);
    }

    /**
     * Creates an AttributeModifier that appends the value to the current value of the
     * attribute, and will add the attribute when it is not there already.
     *
     * @param attribute
     *            the attribute to append the appendModels value to
     * @param value
     *            the value to append
     * @param separator
     *            the separator string, comes between the original value and the append value
     */
    public AttributeAppender(String attribute, Serializable value, String separator) {
        super(attribute, value);
        setSeparator(separator);
    }

    /**
     * Creates an AttributeModifier that appends the appendModel's value to the current value of the
     * attribute, and will add the attribute when it is not there already.
     * 
     * @param attribute
     *            the attribute to append the appendModels value to
     * @param appendModel
     *            the model supplying the value to append
     * @param separator
     *            the separator string, comes between the original value and the append value
     */
    public AttributeAppender(String attribute, IModel<?> appendModel, String separator) {
        super(attribute, appendModel);
        setSeparator(separator);
    }

    /**
     * Gets the separator used by attribute appenders and prependers.
     * 
     * @return the separator used by attribute appenders and prependers.
     */
    public String getSeparator() {
        return separator;
    }

    /**
     * Sets the separator used by attribute appenders and prependers.
     * 
     * @param separator
     *            a space, semicolon or other character used to separate the current value and the
     *            appended/prepended value.
     * @return this
     */
    public AttributeAppender setSeparator(String separator) {
        this.separator = separator;
        return this;
    }

    @Override
    protected Serializable newValue(String currentValue, String appendValue) {
        // Short circuit when one of the values is empty: return the other value.
        if (Strings.isEmpty(currentValue)) {
            return appendValue != null ? appendValue : null;
        } else if (Strings.isEmpty(appendValue)) {
            return currentValue;
        }
        StringBuilder sb = new StringBuilder(currentValue);
        sb.append((getSeparator() == null ? "" : getSeparator()));
        sb.append(appendValue);
        return sb.toString();
    }

    @Override
    public String toString() {
        String attributeModifier = super.toString();
        attributeModifier = attributeModifier.substring(0, attributeModifier.length() - 2) + ", separator="
                + separator + "]";
        return attributeModifier;
    }
}