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33 lines
1 KiB
Markdown
33 lines
1 KiB
Markdown
General Rules
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=============
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All classes which subclass `TopLevelStreamElement` and `ExtensionElement` must either
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1. be immutable (and ideally provide a Builder)
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2. implement `TypedCloneable`
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and must be `Serializable`.
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The reason that it must be either 1. or 2. is that it makes no sense to clone an inmutable instance.
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The preferred option is 1.
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Note that there is legacy code in Smack which does not follow these rules. Patches are welcome.
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ExtensionElement
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================
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Extension elements are XML elements that are used in various parts and levels of stanzas.
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The static `from(Stanza)` Method
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--------------------------------
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Every ExtensionElement class must have a static `from()` method that retrieves that extension for a given Stanza (if any).
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Sample Code
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```java
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public static RSMSet from(Stanza) {
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return packet.getExtension(ELEMENT, NAMESPACE);
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}
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```
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Sometimes certain ExtensionElement's are only found in one stanza type, in that case, specify the parameter type. For example `public static CarbonExtension getFrom(Message)`.
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