Gravel是为JSF应用程序提供的组件库，它主要包括下面几个标签：
ga
This set of tags provide a set of action-related components. The tags support various response-time actions, security role-checking, and other related utilities.
gc
This tag namespace provides a version of `dataTable` that does not suffer from the state-saving difficulties of the standard implementation.
gd
This set of tags provide components, converters, and actions for the manipulation and display of data.
gs
This namespace consists of JSF component versions of standard HTML tags.
n
This namespace is for use with the Gravel navigation handler, which allows navigation rules to be mapped directly in the page instead of inside `faces-config.xml`.
