-Content to be added. +The Smack provider architecture is a system for plugging in +custom XML parsing of packet extensions and IQ packets. The +standard Smack Extensions +are built using the provider architecture. Two types of +providers exist:
IQProvider
+ +By default, Smack only knows how to process IQ packets with sub-packets that +are in a few namespaces such as:+ <?xml version="1.0"?> + <smackProviders> + <iqProvider> + <elementName>query</elementName> + <namespace>jabber:iq:time</namespace> + <className>org.jivesoftware.smack.packet.Time</className> + </iqProvider> + </smackProviders>+ +Each IQ provider is associated with an element name and a namespace. In the +example above, the element name is query and the namespace is +abber:iq:time. If multiple provider entries attempt to register to +handle the same namespace, the first entry loaded from the classpath will +take precedence.
+ +The IQ provider class can either implement the IQProvider +interface, or extend the IQ class. In the former case, each IQProvider is +responsible for parsing the raw XML stream to create an IQ instance. In +the latter case, bean introspection is used to try to automatically set +properties of the IQ instance using the values found in the IQ packet XML. +For example, an XMPP time packet resembles the following: + +
+<iq type='result' to='joe@example.com' from='mary@example.com' id='time_1'> + <query xmlns='jabber:iq:time'> + <utc>20020910T17:58:35</utc> + <tz>MDT</tz> + <display>Tue Sep 10 12:58:35 2002</display> + </query> +</iq>+ +In order for this packet to be automatically mapped to the Time object listed in the +providers file above, it must have the methods setUtc(String), setTz(String), and +setDisplay(String). The introspection service will automatically try to convert the String +value from the XML into a boolean, int, long, float, double, or Class depending on the +type the IQ instance expects.
+ +
PacketExtensionProvider
+ +Packet extension providers provide a pluggable system for +packet extensions, which are child elements in a custom namespace +of message and presence packets (IQ packets cannot have packet extensions). +Each extension provider is registered with an element name and namespace +in the smack.providers file as in the following example: + ++<?xml version="1.0"?> +<smackProviders> + <extensionProvider> + <elementName>x</elementName> + <namespace>jabber:iq:event</namespace> + <className>org.jivesoftware.smack.packet.MessageEvent</className> + </extensionProvider> +</smackProviders>+ +If multiple provider entries attempt to register to handle the same element +name and namespace, the first entry loaded from the classpath will take +precedence.
+ +Whenever a packet extension is found in a packet, parsing will +be passed to the correct provider. Each provider can either implement the +PacketExtensionProvider interface or be a standard Java Bean. In the +former case, each extension provider is responsible for parsing the raw +XML stream to contruct an object. In the latter case, bean introspection +is used to try to automatically set the properties of the class using +the values in the packet extension sub-element.
+
+When an extension provider is not registered for an element name and
+namespace combination, Smack will store all top-level elements of the
+sub-packet in DefaultPacketExtension object and then attach it to the packet.
+