使用场景:

如果action针对每次请求都要执行一些相同的业务逻辑， 那么可以实现Preparable接口，将预处理业务逻辑写在prepare()方法里

 

Preparable 接口定义:

public interface Preparable {

    void prepare() throws Exception;

}

 

prepare何时被执行:

prepare方法由PrepareInterceptor拦截器调用执行

com.opensymphony.xwork2.interceptor.PrepareInterceptor

    public String doIntercept(ActionInvocation invocation) throws Exception {

        Object action = invocation.getAction();

       if (action instanceof Preparable) {

            try {

                String[] prefixes;

                if (firstCallPrepareDo) {

                    prefixes = new String[] {ALT_PREPARE_PREFIX, PREPARE_PREFIX};

                } else {

                    prefixes = new String[] {PREPARE_PREFIX, ALT_PREPARE_PREFIX};

                }

                PrefixMethodInvocationUtil.invokePrefixMethod(invocation, prefixes);

            }

            catch (InvocationTargetException e) {

                // just in case there's an exception while doing reflection,

                // we still want prepare() to be able to get called.

                LOG.warn("an exception occured while trying to execute prefixed method", e);

            }

            catch (IllegalAccessException e) {

                // just in case there's an exception while doing reflection,

                // we still want prepare() to be able to get called.

                LOG.warn("an exception occured while trying to execute prefixed method", e);

            } catch (Exception e) {

                // just in case there's an exception while doing reflection,

                // we still want prepare() to be able to get called.

                LOG.warn("an exception occured while trying to execute prefixed method", e);

            }

            // 必须执行或初始化的一些业务操作 action prepare()方法

            if (alwaysInvokePrepare) {

                ((Preparable) action).prepare();

            }

        }

       return invocation.invoke();

    }

 

使用方法:

使用basicStack拦截器栈

<action name="list" class="org.apache.struts2.showcase.action.SkillAction" method="list">

 <result>/empmanager/listSkills.jsp</result>

 <interceptor-ref name="basicStack" />    <!-- 使用basicStack拦截器栈, 该拦截器栈在 struts-default.xml 已配置, 包括了prepare -->

</action>

(注: struts-default.xml  里定义的 basicStack拦截器栈

    <!-- Basic stack -->

            <interceptor-stack name="basicStack">

                <interceptor-ref name="exception"/>

                <interceptor-ref name="servletConfig"/>

                <interceptor-ref name="prepare"/>

                <interceptor-ref name="checkbox"/>

                <interceptor-ref name="multiselect"/>

                <interceptor-ref name="actionMappingParams"/>

                <interceptor-ref name="params">

                    <param name="excludeParams">dojo\..*,^struts\..*</param>

                </interceptor-ref>

                <interceptor-ref name="conversionError"/>

            </interceptor-stack>

)

或者直接指定prepare拦截器

<action name="list" class="org.apache.struts2.showcase.action.SkillAction" method="list">

 <result>/empmanager/listSkills.jsp</result>

 <interceptor-ref name="prepare" />   <!-- 直接指定prepare拦截器 -->

</action>