The org.zkoss.xel.VariableResolver interface
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The org.zkoss.xel.VariableResolver Interface [since 5.0.4]
VariableResolver is implemented by a listener class that will be used as the default variable resolver of each page. In other words, the variable resolver defined will be available to all pages.
ZK will instantiate an instance of the given class for each page, so the variable resolver is no need to be thread safe.
This feature is useful for tools and utilities to provide the default variable resolvers (aka., implicit variables). A tool can specify the listeners in metainfo/zk/config.xml (locatable by the class loader) -- not just in WEB-INF/zk.xml.