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448 lines
No EOL
16 KiB
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<html>
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<head>
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<title>PubSub</title>
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<link rel="stylesheet" type="text/css" href="style.css" />
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</head>
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<body>
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<div class="header">Pubsub</div><p>
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This section details the usage of an API designed for accessing an XMPP based
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implementation of a <a href="http://en.wikipedia.org/wiki/Publish/subscribe">publish and subscribe</a>
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based messaging system. It has functionality for creation, configuration of,
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subscription and publishing to pubsub nodes.<p>
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<ul>
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<li><a href="#create">Node creation and configuration</a></li>
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<li><a href="#publish">Publishing to a node</a></li>
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<li><a href="#subscribe">Receiving pubsub messages</a></li>
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<li><a href="#retrieve">Retrieving persisted pubsub messages</a></li>
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<li><a href="#discopubsub">Discover pubsub information</a></li>
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</ul>
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<b>XEP related:</b> <a href="http://xmpp.org/extensions/xep-0060.html">XEP-0060</a>
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<hr>
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<div class="subheader"><a name="create">Node creation and configuration</a></div><p>
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<b>Description</b><p>
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Allowed users may create and configure pubsub nodes. There are two types of nodes that can be created,
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leaf nodes and collection nodes.
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<li>Leaf Nodes - contains only messages</li>
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<li>Collection Nodes - contains only nodes (both Leaf and Collection are allowed), but no messages</li>
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The current version of this API only supports Leaf Nodes.
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There are many configuration options available for nodes, but the two main options are whether the node
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is <b>persistent</b> or not and whether it will deliver payload or not.</p>
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<b>Usage</b><p>
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In order to create a node you will need to first create an instance of <i><b>PubSubManager</b></i>. There
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are several options for node creation which range from creating an instant node, default configuration, or
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a fully configured node.</p><p>
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<b>Examples</b><p>
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Create an instant node: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Create the node</font>
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LeafNode leaf = mgr.createNode();
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</pre>
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</blockquote>
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Create a node with default configuration and then configure it: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Create the node</font>
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LeafNode leaf = mgr.createNode(<font color="#0000FF">"testNode"</font>);
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ConfigureForm form = new ConfigureForm(FormType.submit);
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form.setAccessModel(AccessModel.open);
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form.setDeliverPayloads(false);
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form.setNotifyRetract(true);
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form.setPersistentItems(true);
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form.setPublishModel(PublishModel.open);
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leaf.sendConfigurationForm(form);
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</pre>
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</blockquote>
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Create and configure a node: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Create the node</font>
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ConfigureForm form = new ConfigureForm(FormType.submit);
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form.setAccessModel(AccessModel.open);
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form.setDeliverPayloads(false);
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form.setNotifyRetract(true);
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form.setPersistentItems(true);
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form.setPublishModel(PublishModel.open);
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LeafNode leaf = mgr.createNode(<font color="#0000FF">"testNode"</font>, form);
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</pre>
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</blockquote>
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<hr>
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<div class="subheader"><a name="publish">Publishing to a node</a></div><p>
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<b>Description</b><p>
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This section deals with the <b>publish</b> portion of pubsub.
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Usage of a node typically involves either sending or receiving data, referred to as items.
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Depending on the context of the nodes usage, the item being sent to it can have different
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properties.
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It can contain application data known as payload, or the publisher may choose to supply
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meaningful unique id's. Determination of an items acceptable properties is defined by a
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combination of node configuration and its purpose.
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</p>
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<b>Usage</b><p>
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To publish to a node, you will have to either create or retrieve an existing node and then
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create and send items to that node. The ability for any given person to publish to the node
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will be dependent on its configuration.
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</p>
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<b>Examples</b><p>
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In this example we publish an item to a node that does not take payload: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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<font color="#3f7f5f">// Publish an Item, let service set the id</font>
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node.send(new Item());
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<font color="#3f7f5f">// Publish an Item with the specified id</font>
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node.send(new Item(<font color="#0000FF">"123abc"</font>));
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</pre>
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</blockquote>
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In this example we publish an item to a node that does take payload: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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<font color="#3f7f5f">// Publish an Item with payload</font>
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node.send(new PayloadItem<SimplePayload>(<font color="#0000FF">"test"</font> + System.currentTimeMillis(),
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new SimplePayload(<font color="#0000FF">"book"</font>, <font color="#0000FF">"pubsub:test:book"</font>, <font color="#0000FF">"<book xmlns='pubsub:test:book'><title>Two Towers</title></book>"</font>)));
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</pre>
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</blockquote>
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<div class="subheader"><a name="subscribe">Receiving pubsub messages</a></div><p>
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<b>Description</b><p>
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This section deals with the <b>subscribe</b> portion of pubsub.
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As mentioned in the last section, usage of a node typically involves either sending or receiving
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items. Subscribers are interested in being notified when items are published to the pubsub
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node. These items may or may not have application specific data (payload), as that
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is dependent on the context in which the node is being used.
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</p>
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<b>Usage</b><p>
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To get messages asynchronously when items are published to a node, you will have to
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<li>Get a node.</li>
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<li>Create and register a listener.</li>
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<li>Subscribe to the node.</li>
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<p>
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Please note that you should register the listener before subscribing so that all messages
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sent after subscribing are received. If done in the reverse order, messages that are sent
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after subscribing but before registering a listener may not be processed as expected.
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</p></p>
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<b>Examples</b><p>
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In this example we can see how to create a listener and register it and then subscribe for
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messages. <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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node.addItemEventListener(new ItemEventCoordinator<Item>());
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node.subscribe(myJid);
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</pre>
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</blockquote>
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Where the listener is defined like so:
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<blockquote>
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<pre>
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class ItemEventCoordinator <T extends Item> implements ItemEventListener<T>
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{
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@Override
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public void handlePublishedItems(ItemPublishEvent<T> items)
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{
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System.out.println(<font color="#0000FF">"Item count: "</font> + items.getItems().size());
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System.out.println(items);
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}
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}
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</pre>
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</blockquote>
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In addition to receiving published items, there are notifications for several other
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events that occur on a node as well.
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<li>Deleting items or purging all items from a node</li>
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<li>Changing the node configuration</li>
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<p>
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In this example we can see how to create a listener, register it and then subscribe for
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item deletion messages. <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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node.addItemDeleteListener(new ItemDeleteCoordinator<Item>());
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node.subscribe(myJid);
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node.deleteItem(<font color="#0000FF">"id_one"</font>);
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</pre>
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</blockquote>
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Where the handler is defined like so:
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<blockquote>
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<pre>
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class ItemDeleteCoordinator implements ItemDeleteListener<T>
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{
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@Override
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public void handleDeletedItems(ItemDeleteEvent items)
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{
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System.out.println(<font color="#0000FF">"Item count: "</font> + items.getItemIds().size());
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System.out.println(items);
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}
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@Override
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public void handlePurge()
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{
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System.out.println(<font color="#0000FF">"All items have been deleted from node"</font>);
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}
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}
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</pre>
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</blockquote>
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In this example we can see how to create a listener, register it and then subscribe for
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node configuration messages. <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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Node node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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node.addConfigurationListener(new NodeConfigCoordinator());
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node.subscribe(myJid);
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ConfigureForm form = new ConfigureForm(FormType.submit);
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form.setAccessModel(AccessModel.open);
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form.setDeliverPayloads(false);
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form.setNotifyRetract(true);
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form.setPersistentItems(true);
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form.setPublishModel(PublishModel.open);
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node.sendConfigurationForm(form);
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</pre>
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</blockquote>
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Where the handler is defined like so:
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<blockquote>
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<pre>
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class NodeConfigCoordinator implements NodeConfigListener<T>
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{
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@Override
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public void handleNodeConfiguration(ConfigurationEvent config)
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{
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System.out.println(<font color="#0000FF">"New configuration"</font>);
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System.out.println(config.getConfiguration());
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}
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}
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</pre>
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</blockquote>
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<hr>
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<div class="subheader"><a name="retrieve">Retrieving persisted pubsub messages</a></div><p>
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<b>Description</b><p>
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When persistent nodes are used, the subscription and registration methods described in the last section
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will not enable the retrieval of items that already exist in the node. This section deals with the
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specific methods for retrieving these items.
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There are several means of retrieving existing items. You can retrieve all items at once, the last N
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items, or the items specified by a collection of id's.
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Please note that the service may, according to the pubsub specification, reply with a list of items
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that contains only the item id's (no payload) to save on bandwidth. This will not occur when the id's
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are specified since this is the means of guaranteeing retrieval of payload.</p>
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<b>Usage</b><p>
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To synchronously retrieve existing items from a persistent node, you will have to get an instance
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of a <i><b>LeafNode</b></i> and call one of the retrieve methods.
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<p>
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<b>Examples</b><p>
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In this example we can see how to retrieve the existing items from a node: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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Collection<? extends Item> items = node.getItems();
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</pre>
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</blockquote>
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In this example we can see how to retrieve the last N existing items: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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List<? extends Item> items = node.getItems(100);
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</pre>
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</blockquote>
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In this example we can see how to retrieve the specified existing items: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the node</font>
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LeafNode node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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Collection<String> ids = new ArrayList<String>(3);
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ids.add("1");
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ids.add("3");
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ids.add("4");
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List<? extends Item> items = node.getItems(ids);
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</pre>
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</blockquote>
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<hr>
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<div class="subheader"><a name="discopubsub">Discover pubsub information</a></div><p>
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<b>Description</b><p>
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A user may want to query a server or node for a variety of pubsub related information.</p>
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<b>Usage</b><p>
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To retrieve information, a user will simply use either the <i><b>PubSubManager</b></i>
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or <i><b>Node</b></i> classes depending on what type of information is required.
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<b>Examples</b><p>
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In this example we can see how to get pubsub capabilities: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the pubsub features that are supported</font>
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DiscoverInfo supportedFeatures = mgr.getSupportedFeatures();
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</pre>
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</blockquote>
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In this example we can see how to get pubsub subscriptions for all nodes: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get all the subscriptions in the pubsub service</font>
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List<Subscription> subscriptions = mgr.getSubscriptions();
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</pre>
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</blockquote>
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In this example we can see how to get all affiliations for the users bare JID on the pubsub service: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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<font color="#3f7f5f">// Get the affiliations for the users bare JID</font>
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List<Affiliation> affiliations = mgr.getAffiliations();
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</pre>
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</blockquote>
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In this example we can see how to get information about the node: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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Node node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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<font color="#3f7f5f">// Get the node information</font>
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DiscoverInfo nodeInfo = node.discoverInfo();
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</pre>
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</blockquote>
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In this example we can see how to discover the node items: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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Node node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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<font color="#3f7f5f">// Discover the node items</font>
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DiscoverItems nodeItems = node.discoverItems();
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</pre>
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</blockquote>
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In this example we can see how to get node subscriptions: <br>
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<blockquote>
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<pre>
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<font color="#3f7f5f">// Create a pubsub manager using an existing XMPPConnection</font>
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PubSubManager mgr = new PubSubManager(con);
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Node node = mgr.getNode(<font color="#0000FF">"testNode"</font>);
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<font color="#3f7f5f">// Discover the node subscriptions</font>
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List<Subscription> subscriptions = node.getSubscriptions();
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</pre>
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</blockquote>
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<hr>
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</body>
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</html> |