The namespace attribute subdivides action configurations into logical modules, each with its own identifying prefix. Namespaces avoid conflicts between action names. Each namespace can have it's own "menu" or "help" action, each with its own implementation. While the prefix appears in the browser URI, the tags are "namespace aware", so the namespace prefix does not need to be embedded in forms and links.
Namespace属性细分了action配置到逻辑模块，每个都有自己的唯一的前缀，Namespace避免了action之间名称的冲突，每个namespace能有他自己的“menu”或“help”action，每个有自己的实现。当前缀在浏览器URI中出现时，标签能够用namespace感知，所以namespace前缀不需要嵌套在Form和Link里。
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Namespaces are the equivalent of Struts Action 1 modules. |
Default Namespace
The default namespace is "" - an empty string. The default namespace is used as a "catch-all" namespace. If an action configuration is not found in a specified namespace, the default namespace is also be searched. The local/global strategy allows an application to have global action configurations outside of the action element "extends" hierarchy.
The namespace prefix can be registered with Java declarative security, to ensure only authorized users can access the actions in a given namespace.
namespace前缀能够被Java申明安全注册，来确保只有授权用户访问给定命名空间的action。
Root Namespace
A root namespace ("/") is also supported. The root is the namespace when a request directly under the context path is received. As with other namespace, it will fall back to the default ("") namespace if a local action is not found.
Namespace Example
<package name="default">
<action name="foo" class="mypackage.simpleAction>
<result name="success" type="dispatcher">greeting.jsp</result>
</action>
<action name="bar" class="mypackage.simpleAction">
<result name="success" type="dispatcher">bar1.jsp</result>
</action>
</package>
<package name="mypackage1" namespace="/">
<action name="moo" class="mypackage.simpleAction">
<result name="success" type="dispatcher">moo.jsp</result>
</action>
</package>
<package name="mypackage2" namespace="/barspace">
<action name="bar" class="mypackage.simpleAction">
<result name="success" type="dispatcher">bar2.jsp</result>
</action>
</package>
How the Code Works
If a request for /barspace/bar.action is made, /barspace namespace is searched and if it is found the bar action is executed, else it will fall back to the default namespace. In the Namespace Example, the bar action does exists in the barspace namespace. The barspace.bar action will be executed, and if "success" is returned, the request will be forwarded to bar2.jsp.
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Falling Back to Foo
If a request is made to /barspace/foo.action, the namespace /barspace will be checked for action foo. If a local action is not found, the default namespace is checked. In the Namespace Example, there is no action foo in the namespace /barspace, therefore the default will be checked and /foo.action will be executed.
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In the Namespace Example, if a request for moo.action is made, the root namespace ('/') is searched for a moo action; if a root action is not found, the default namespace is checked. In this case, the moo action does exist and will be selected. Upon success, the request would be forwarded to bar2.jsp.
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Getting to the Root
If a request is made for /foo.action, the root / namespace will be checked. If foo is found, the root action will be selected. Otherwise, the framework will check the default namespace. In the Namespace Example, foo action does not exist in the root namespace, so the default namespace is checked, and the default foo action is selected. |
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Namespaces are not a path!
Namespace are not hierarchical like a file system path. There is one namespace level. For example if the URL /barspace/myspace/bar.action is requested, the framework will first look for namespace /barspace/myspace. If the action does not exist at /barspace/myspace, the search will immediately fall back to the default namespace "". The framework will not parse the namespace into a series of "folders". In the Namespace Example, the bar
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