org.directwebremoting.io.Item Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * Licensed 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.directwebremoting.io;

import java.util.Map;

import org.directwebremoting.datasync.ExposeToString;

/**
 * Analogous to a {@link java.util.Map.Entry} that we use to pass objects that
 * have been stored in a {@link org.directwebremoting.datasync.StoreProvider} to
 * the Internet.
 * TODO: Consider if we should add version field to this so we can add some sort
 * of pessimistic locking to updates.
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class Item
{
    /**
     * Create an Item with its ID and data.
     */
    public Item(String itemId, Object data)
    {
        this.itemId = itemId;
        this.data = data;
    }

    /**
     * Create an Item with its ID and data from a {@link java.util.Map.Entry}
     */
    public Item(Map.Entry entry)
    {
        this.itemId = entry.getKey();
        this.data = entry.getValue();
    }

    /**
     * Accessor for the primary key for this Object.
     * Clearly not all database primary keys are Strings, my current feeling is
     * that the majority of database primary keys can either be simply mapped to
     * strings, or are a bad idea anyway.
     * Warning: It would be a bad idea to expose database primary keys
     * directly to the Internet anyway, so some form of mapping is required.
     * @return The primary key for this Object
     */
    public String getItemId()
    {
        return itemId;
    }

    /**
     * The object that is referred to by the itemId.
     * @return The real data
     */
    public Object getData()
    {
        return data;
    }

    /**
     * Items need labels to support dojo.data.api.Read.getLabel()
     * By default we just use the itemId, however if the data implements
     * {@link ExposeToString} then consider {@link Object#toString()}
     * to be safe for Internet use.
     * @return A label for this object
     */
    public String getLabel()
    {
        if (data.getClass().isAnnotationPresent(ExposeToString.class))
        {
            return data.toString();
        }
        else
        {
            return itemId;
        }
    }

    /* (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode()
    {
        return 4783 + itemId.hashCode();
    }

    /* (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj)
    {
        if (obj == null)
        {
            return false;
        }

        if (obj == this)
        {
            return true;
        }

        if (!this.getClass().equals(obj.getClass()))
        {
            return false;
        }

        Item that = (Item) obj;

        if (!this.itemId.equals(that.itemId))
        {
            return false;
        }

        return true;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString()
    {
        return "Item[" + itemId + "]";
    }

    /**
     * @see #getItemId
     */
    private final String itemId;

    /**
     * @see #getData
     */
    private final Object data;
}