• struts2 Preparable接口


    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>

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  • 原文地址:https://www.cnblogs.com/mount/p/2241046.html
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