Struts2的拦截器

1.拦截器的重要性

Struts2中的很多功能都是由拦截器完成的。比如：servletConfig，staticParam，params，modelDriven等等。
是AOP编程思想的一种应用形式。

2.拦截器的执行时机

时机.png

3.自定义拦截器

3.1、拦截器的类试图

自定义拦截器.png

3.2编写步骤

• a.编写一个类，继承AbstractInterceptor类或者实现Interceptor接口。重写intercept方法

public class Demo1Interceptor extends AbstractInterceptor {
    @Override
    public String intercept(ActionInvocation actionInvocation) throws Exception {
        System.out.println("拦截前");
        //放行
        String invoke = actionInvocation.invoke();
        System.out.println("拦截后");
        return invoke;
    }
}

• b.配置拦截器：注意拦截器必须先声明再使用

<package name="pp1" extends="struts-default">
        <!--使用自定义拦截器-->
        <interceptors>
            <interceptor name="demo1Interceptor" class="com.ljb.interceptor.Demo1Interceptor"></interceptor>
        </interceptors>
        <action name="action1" class="com.ljb.web.Demo1Action" method="save">
            <interceptor-ref name="demo1Interceptor"></interceptor-ref>
            <result>/success.jsp</result>
        </action>
    </package>

3.3.执行顺序

public class Demo1Action extends ActionSupport {

    public String save() throws Exception {
        System.out.println("doAction");
        return "success";
    }
}

拦截前
doAction
拦截后

3.4.多个拦截器

<package name="pp1" extends="struts-default">
        <!--使用自定义拦截器-->
        <interceptors>
            <interceptor name="demo1Interceptor" class="com.ljb.interceptor.Demo1Interceptor"></interceptor>
            <interceptor name="demo2Interceptor" class="com.ljb.interceptor.Demo1Interceptor2"></interceptor>
        </interceptors>
        <action name="action1" class="com.ljb.web.Demo1Action" method="save">
            <interceptor-ref name="demo1Interceptor"></interceptor-ref>
            <interceptor-ref name="demo2Interceptor"></interceptor-ref>
            <result>/success.jsp</result>
        </action>
    </package>

4.拦截器的应用

public class Demo1Interceptor extends MethodFilterInterceptor {

    @Override
    protected String doIntercept(ActionInvocation actionInvocation) throws Exception {
        System.out.println("拦截前");
        //放行
        String invoke = actionInvocation.invoke();
        System.out.println("拦截后");
        return invoke;
    }
}

<constant name="struts.devMode" value="true"> </constant>
    <package name="pp1" extends="struts-default" >
        <!--使用自定义拦截器-->
        <interceptors>
            <interceptor name="demo1Interceptor" class="com.ljb.interceptor.Demo1Interceptor"/>
            <interceptor-stack name="myInterceptor">
                <interceptor-ref name="defaultStack"></interceptor-ref>
                <interceptor-ref name="demo1Interceptor"></interceptor-ref>
            </interceptor-stack>
        </interceptors>
        <default-interceptor-ref name="myInterceptor"></default-interceptor-ref>

        <global-results>
            <result name="input">/success.jsp</result>
        </global-results>

        <action name="action1" class="com.ljb.web.Demo1Action" method="save">
            <interceptor-ref name="myInterceptor">
                <param name="demo1Interceptor.excludeMethods">save</param>
            </interceptor-ref>
            <result>/success.jsp</result>
        </action>
    </package>

拦截器类视图（全）

自定义拦截器.png