struts.xml 模块化管理

先贴两段代码，在慢慢解释

(1)struts-user.xml

<struts> 
    <package name="struts-user" extends="struts-default"> 
        <global-results> 
            <result type="redirect-action">UserAction_queryAll</result> 
        </global-results> 
        <action name="UserAction_login" class="userAction" method="login"></action> 
        <action name="UserAction_insert" class="userAction" method="insert"></action> 
        <action name="UserAction_update" class="userAction" method="update"></action> 
        <action name="UserAction_delete" class="userAction" method="delete"></action> 
        <action name="UserAction_queryById" class="userAction" method="queryById"></action>  
        <action name="UserAction_queryByLike" class="userAction" method="queryByLike"></action> 
        <action name="UserAction_queryAll" class="userAction" method="queryAll"> 
            <result>/user/user_list.jsp</result> 
        </action> 
          </package> 
</struts>

(2)struts.xml(引入了struts-user.xml)

<struts> 
    <include file="struts-user.xml"></include> 
    <package name="struts" extends="struts-default"></package> 
</struts>

1. 使用<include>标签重用配置文件

(1)在Struts2中提供了一个默认的struts.xml文件，但如果package、action、interceptors等配置比较多时，都放到一个struts.xml文件不太容易维护。因此，就需要将struts.xml文件分成多个配置文件，然后在struts.xml文件中使用<include>标签引用这些配置文件。如上面的代码。

注意：用<include>引用的xml文件也必须是完成的struts2的配置。实际上<include>在引用时是单独解析的xml文件，而不是将被引用的文件插入到struts.xml文件中。

注意：struts.xml和struts-user.xml中<package></package>标签中的name属性不能相同。道理很简单，<struts></struts>标签中可以有多个<package></package>标签，要通过name属性以示区别。

(2)Apache Struts 2 Documentation: Can we break up a large struts.xml file into smaller pieces --> Yes, there are two approaches. We can include other struts.xml file from a bootstrap, or we can package a struts.xml files in a JAR. Or both.

<1>By Include：A typical struts.xml files will have one or more include elements:

<struts>
    <include file="struts-default.xml"/>
    <include file="config-browser.xml"/>
    <package name="default" extends="struts-default">
    ....
    </package>
    <include file="other.xml"/>
</struts>
The first include element tells the framework to load the struts-default.xml, which it will find in the struts2.jar file. The struts-default.xml file defines the "standard" interceptor and result definitions. You can put your own <include> elements in your struts.xml interchangeably with <package> elements. The configuration objects will be loaded in the order of appearance. The framework reads the configuration from top to bottom and adds objects as they are referenced.

<2>By JAR

A "module" can be added to an application by placing a struts.xml and related classes into a JAR on the classpath. FreeMarker and Velocity templates can also be provided by JAR, making it possible to distribution a module in a single, self-contained JAR that is automatically configured on startup.

2. 全局result(global-results)

(1)有很多时候一个<result>可供很多<action>使用，这时可以使用<global-results>标签来定义全局的<result>，代码见struts-user.xml。执行顺序：当一个Action返回的String没有相应的<result>与之对应，Struts2就会查找全局的<result>。

(2)Apache Struts 2 Documentation: Global Results

Most often, results are nested with the action element. But some results apply to multiple actions. In a secure application, a client might try to access a page without being authorized, and many actions may need access to a "logon" result. If actions need to share results, a set of global results can be defined for each package. The framework will first look for a local result nested in the action. If a local match is not found, then the global results are checked.

<!-- Defining global results -->
<global-results>
    <result name="error">/Error.jsp</result>
    <result name="invalid.token">/Error.jsp</result>
    <result name="login" type="redirectAction">Logon!input</result>
</global-results>
3. <include>标签和<global-results>标签结合

(1)<global-results>标签的作用域只是当前<struts></struts>，也可以说是当前的xml文件；struts2不允许把struts-user.xml(通过<include>引入到struts.xml)中的<global-results>标签写在struts.xml中。
(2)如果struts-user.xml中的package继承自struts.xml中的package，则可以将struts-user.xml中的<global-results>放在struts.xml中。然后struts-user.xml将此<global-results>从struts.xml中继承过来。例如(将上面的两段代码简单修改)：

(1)struts-user.xml

<struts> 
    <!-- 这里struts-user继承(extends)的是struts, 即struts.xml中package的name属性值 --> 
    <package name="struts-user" extends="struts"> 
         
        <action name="UserAction_login" class="userAction" method="login"></action> 
        <action name="UserAction_insert" class="userAction" method="insert"></action> 
        <action name="UserAction_update" class="userAction" method="update"></action> 
        <action name="UserAction_delete" class="userAction" method="delete"></action> 
        <action name="UserAction_queryById" class="userAction" method="queryById"></action>  
        <action name="UserAction_queryByLike" class="userAction" method="queryByLike"></action> 
        <action name="UserAction_queryAll" class="userAction" method="queryAll"> 
            <result>/user/user_list.jsp</result> 
        </action> 
    </package> 
</struts>

(2)struts.xml(引入了struts-user.xml)

<struts> 
    <include file="struts-user.xml"></include> 
    <package name="struts" extends="struts-default"> 
        <global-results> 
            <result type="redirect-action">UserAction_queryAll</result> 
        </global-results> 
    </package> 
</struts>