001/**
002 *
003 * Copyright the original author or authors
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.jivesoftware.smackx.pubsub;
018
019import org.jivesoftware.smack.packet.Message;
020
021import org.jivesoftware.smackx.pubsub.provider.ItemProvider;
022
023/**
024 * This class represents an item that has been, or will be published to a
025 * PubSub node.  An <tt>Item</tt> has several properties that are dependent
026 * on the configuration of the node to which it has been or will be published.
027 * 
028 * <h3>An Item received from a node (via {@link LeafNode#getItems()} or {@link LeafNode#addItemEventListener(org.jivesoftware.smackx.pubsub.listener.ItemEventListener)}</h3>
029 * <ul>
030 * <li>Will always have an id (either user or server generated) unless node configuration has both
031 * {@link ConfigureForm#isPersistItems()} and {@link ConfigureForm#isDeliverPayloads()}set to false.
032 * <li>Will have a payload if the node configuration has {@link ConfigureForm#isDeliverPayloads()} set 
033 * to true, otherwise it will be null.
034 * </ul>
035 * 
036 * <h3>An Item created to send to a node (via {@link LeafNode#send()} or {@link LeafNode#publish()}</h3>
037 * <ul>
038 * <li>The id is optional, since the server will generate one if necessary, but should be used if it is 
039 * meaningful in the context of the node.  This value must be unique within the node that it is sent to, since
040 * resending an item with the same id will overwrite the one that already exists if the items are persisted.
041 * <li>Will require payload if the node configuration has {@link ConfigureForm#isDeliverPayloads()} set
042 * to true.
043 * </ul>
044 * 
045 * <p>
046 * To customise the payload object being returned from the {@link PayloadItem#getPayload()} method, you can
047 * add a custom parser as explained in {@link ItemProvider}.
048 * </p>
049 * 
050 * @author Robin Collier
051 */
052public class Item extends NodeExtension
053{
054    private String id;
055
056    /**
057     * Create an empty <tt>Item</tt> with no id.  This is a valid item for nodes which are configured
058     * so that {@link ConfigureForm#isDeliverPayloads()} is false.  In most cases an id will be generated by the server.
059     * For nodes configured with {@link ConfigureForm#isDeliverPayloads()} and {@link ConfigureForm#isPersistItems()}
060     * set to false, no <tt>Item</tt> is sent to the node, you have to use {@link LeafNode#send()} or {@link LeafNode#publish()}
061     * methods in this case.
062     */
063    public Item()
064    {
065        super(PubSubElementType.ITEM);
066    }
067
068    /**
069     * Create an <tt>Item</tt> with an id but no payload.  This is a valid item for nodes which are configured
070     * so that {@link ConfigureForm#isDeliverPayloads()} is false.
071     *
072     * @param itemId The id if the item.  It must be unique within the node unless overwriting and existing item.
073     * Passing null is the equivalent of calling {@link #Item()}.
074     */
075    public Item(String itemId)
076    {
077        // The element type is actually irrelevant since we override getNamespace() to return null
078        super(PubSubElementType.ITEM);
079        id = itemId;
080    }
081
082    /**
083     * Create an <tt>Item</tt> with an id and a node id.
084     * <p>
085     * <b>Note:</b> This is not valid for publishing an item to a node, only receiving from
086     * one as part of {@link Message}.  If used to create an Item to publish
087     * (via {@link LeafNode#publish(Item)}, the server <i>may</i> return an
088     * error for an invalid packet.
089     *
090     * @param itemId The id of the item.
091     * @param nodeId The id of the node which the item was published to.
092     */
093    public Item(String itemId, String nodeId)
094    {
095        super(PubSubElementType.ITEM_EVENT, nodeId);
096        id = itemId;
097    }
098
099    /**
100     * Get the item id.  Unique to the node it is associated with.
101     *
102     * @return The id
103     */
104    public String getId()
105    {
106        return id;
107    }
108
109    @Override
110    public String getNamespace()
111    {
112        return null;
113    }
114
115    @Override
116    public String toXML()
117    {
118        StringBuilder builder = new StringBuilder("<item");
119
120        if (id != null)
121        {
122            builder.append(" id='");
123            builder.append(id);
124            builder.append('\'');
125        }
126
127        if (getNode() != null) {
128            builder.append(" node='");
129            builder.append(getNode());
130            builder.append('\'');
131        }
132        builder.append("/>");
133
134        return builder.toString();
135    }
136
137    @Override
138    public String toString()
139    {
140        return getClass().getName() + " | Content [" + toXML() + "]";
141    }
142}