org.apache.wicket.MetaDataKey.java Source code

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Here is the source code for org.apache.wicket.MetaDataKey.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 org.apache.wicket.util.io.IClusterable;

/**
 * A key to a piece of metadata associated with a {@link Component}, {@link Session} or
 * {@link Application} at runtime. The key contains type information that can be used to check the
 * type of any metadata value for the key when the value is set. MetaDataKey is abstract in order to
 * force the creation of a subtype. That subtype is used to test for identity when looking for the
 * metadata because actual object identity would suffer from problems under serialization. So, the
 * correct way to declare a MetaDataKey is like this:
 * 
 * <pre>
 * <code>
 * public static final MetaDataKey&lt;Role&gt; ROLE = new MetaDataKey&lt;Role&gt;() { };
 * </code>
 * </pre>
 * 
 * @author Jonathan Locke
 * 
 * @param <T>
 *            The type of the object which is stored
 * 
 * @see Session#getMetaData(MetaDataKey)
 * @see Component#getMetaData(MetaDataKey)
 * @see Application#getMetaData(MetaDataKey)
 */
public abstract class MetaDataKey<T> implements IClusterable {
    private static final long serialVersionUID = 1L;

    /**
     * Constructor.
     */
    public MetaDataKey() {
    }

    @Override
    public int hashCode() {
        return getClass().hashCode();
    }

    /**
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj) {
        return obj != null && getClass().equals(obj.getClass());
    }

    /**
     * @param metaData
     *            Array of metadata to search
     * @return The entry value
     */
    @SuppressWarnings("unchecked")
    public T get(MetaDataEntry<?>[] metaData) {
        if (metaData != null) {
            for (MetaDataEntry<?> entry : metaData) {
                if (equals(entry.key)) {
                    return (T) entry.object;
                }
            }
        }
        return null;
    }

    /**
     * @param metaData
     *            The array of metadata
     * @param object
     *            The object to set, null to remove
     * @return Any new metadata array (if it was reallocated)
     */
    public MetaDataEntry<?>[] set(MetaDataEntry<?>[] metaData, final Object object) {
        boolean set = false;
        if (metaData != null) {
            for (int i = 0; i < metaData.length; i++) {
                MetaDataEntry<?> m = metaData[i];
                if (equals(m.key)) {
                    if (object != null) {
                        // set new value
                        m.object = object;
                    } else {
                        // remove value and shrink or null array
                        if (metaData.length > 1) {
                            int l = metaData.length - 1;
                            MetaDataEntry<?>[] newMetaData = new MetaDataEntry[l];
                            System.arraycopy(metaData, 0, newMetaData, 0, i);
                            System.arraycopy(metaData, i + 1, newMetaData, i, l - i);
                            metaData = newMetaData;
                        } else {
                            metaData = null;
                        }
                    }
                    set = true;
                    break;
                }
            }
        }
        if (!set && object != null) {
            MetaDataEntry<T> m = new MetaDataEntry<T>(this, object);
            if (metaData == null) {
                metaData = new MetaDataEntry[1];
                metaData[0] = m;
            } else {
                final MetaDataEntry<?>[] newMetaData = new MetaDataEntry[metaData.length + 1];
                System.arraycopy(metaData, 0, newMetaData, 0, metaData.length);
                newMetaData[metaData.length] = m;
                metaData = newMetaData;
            }
        }
        return metaData;
    }

    /**
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return getClass().toString();
    }
}