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83 lines
3.2 KiB
Markdown
83 lines
3.2 KiB
Markdown
Packet Properties
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=================
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Smack provides an easy mechanism for attaching arbitrary properties to
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packets. Each property has a String name, and a value that is a Java primitive
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(int, long, float, double, boolean) or any Serializable object (a Java object
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is Serializable when it implements the Serializable interface).
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Using the API
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-------------
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All major objects have property support, such as Message objects. The
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following code demonstrates how to set properties:
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```
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Message message = chat.createMessage();
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JivePropertiesExtension jpe = new JivePropertiesExtension();
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// Add a Color object as a property._
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jpe.setProperty("favoriteColor", new Color(0, 0, 255));
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// Add an int as a property._
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jpe.setProperty("favoriteNumber", 4);
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// Add the JivePropertiesExtension to the message packet_
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message.addPacketExtension(jpe);
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chat.sendMessage(message);
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```
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Getting those same properties would use the following code:
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```
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Message message = chat.nextMessage();
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// Get the JivePropertiesExtension_
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JivePropertiesExtension jpe = message.getExtension(JivePropertiesExtension.NAMESPACE);
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// Get a Color object property._
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Color favoriteColor = (Color)jpe.getProperty("favoriteColor");
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// Get an int property. Note that properties are always returned as
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// Objects, so we must cast the value to an Integer, then convert
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// it to an int._
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int favoriteNumber = ((Integer)jpe.getProperty("favoriteNumber")).intValue();
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```
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For convenience `JivePropertiesManager` contains two helper methods namely
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`addProperty(Packet packet, String name, Object value)` and
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`getProperty(Packet packet, String name)`.
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Objects as Properties
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---------------------
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Using objects as property values is a very powerful and easy way to exchange
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data. However, you should keep the following in mind:
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* When you send a Java object as a property, only clients running Java will be able to interpret the data. So, consider using a series of primitive values to transfer data instead.
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* Objects sent as property values must implement Serialiable. Additionally, both the sender and receiver must have identical versions of the class, or a serialization exception will occur when de-serializing the object.
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* Serialized objects can potentially be quite large, which will use more bandwidth and server resources.
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XML Format
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----------
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The current XML format used to send property data is not a standard, so will
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likely not be recognized by clients not using Smack. The XML looks like the
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following (comments added for clarity):
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<!-- All properties are in a x block. -->
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<properties xmlns="http://www.jivesoftware.com/xmlns/xmpp/properties">
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<!-- First, a property named "prop1" that's an integer. -->
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<property>
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<name>prop1</name>
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<value type="integer">123</value>
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<property>
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<!-- Next, a Java object that's been serialized and then converted
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from binary data to base-64 encoded text. -->
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<property>
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<name>blah2</name>
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<value type="java-object">adf612fna9nab</value>
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<property>
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</properties>
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The currently supported types are: `integer`, `long`, `float`, `double`,
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`boolean`, `string`, and `java-object`.
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Copyright (C) Jive Software 2002-2008
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