Struts2学习:interceptor(拦截器)的使用

时间:2020-12-05 05:42:25

对于需要登陆验证、权限验证等功能的网站,每一次请求,每一个action都写一段验证的代码,未免显得冗余且不易维护。struts2提供了拦截器interceptor,为这些页面提供一个切面,或者说公共组件,以达到易维护、提高代码重用率的目的。struts默认的interceptor有很多,就不去一一列举,这里从自定义拦截器开始学习。

1、定义一个自定义拦截器:

Struts2学习:interceptor(拦截器)的使用

package com.owlforest.home.interceptor;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class MyInterceptor extends AbstractInterceptor {
    public String intercept(ActionInvocation invocation) throws Exception {
        String output = "Pre-Processing";
        System.out.println(output);

        String result = invocation.invoke();

        output = "Post-Processing";
        System.out.println(output);

        return result;
    }
}

2、修改struts.xml,在package中声明和使用拦截器MyInterceptor

<package name="suibian" extends="struts-default">
        <!--声明自定义的拦截器-->
        <interceptors>
            <interceptor name="myinterceptor"
                         class="com.owlforest.home.interceptor.MyInterceptor" />
        </interceptors>
        <action name="hello" class="com.owlforest.home.action.HelloWorldAction"
                method="excute">
            <!--使用自定义拦截器-->
            <interceptor-ref name="myinterceptor" />
            <interceptor-ref name="params"/>
            <result name="success">/HelloWorld.jsp</result>
        </action>
    </package>

该拦截器在com.owlforest.home.action.HelloWorldAction执行前后会生效,为了便于理解,附上该Action的代码:

package com.owlforest.home.action;

import com.opensymphony.xwork2.ActionSupport;

public class HelloWorldAction extends ActionSupport {
    private String name;

    public String excute(){
        System.out.println("excute");
        return "success";
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

3、执行程序

程序实现参照Struts2学习:HelloWorld

执行action过后可查看控制台输出,看到下面的信息后及说明生效。

Struts2学习:interceptor(拦截器)的使用

4、对于一个struts.xml里面的package,可能有多个action,多个action可能会用到一系列的相同的interceptor,如果每个action都要写一系列相同的拦截器,则很难维护。struts2提供了拦截器栈,来帮助整合这些拦截器,达到复用的目的。

为了方便理解,我写了两个自定义的拦截器MyInterceptor和SecInterceptor

package com.owlforest.home.interceptor;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class MyInterceptor extends AbstractInterceptor {
    public String intercept(ActionInvocation invocation) throws Exception {
        String output = "Pre-Processing  拦截器MyInterceptor";
        System.out.println(output);

        String result = invocation.invoke();

        output = "Post-Processing  拦截器MyInterceptor";
        System.out.println(output);

        return result;
    }
}
package com.owlforest.home.interceptor;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class SecInterceptor extends AbstractInterceptor {
    public String intercept(ActionInvocation invocation) throws Exception {
        String output = "Pre-Processing  SecInterceptor";
        System.out.println(output);

        String result = invocation.invoke();

        output = "Post-Processing  SecInterceptor";
        System.out.println(output);

        return result;
    }
}

配置struts.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
        "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <!-- 设置struts是否为开发模式,默认为false,测试阶段一般设为true. -->
    <constant name="struts.devMode" value="true"/>
    <package name="suibian" extends="struts-default">
        <interceptors>
            <interceptor name="myinterceptor"
                         class="com.owlforest.home.interceptor.MyInterceptor" />
            <interceptor name="secinterceptor"
                         class="com.owlforest.home.interceptor.SecInterceptor" />
            <interceptor-stack name="myinterceptorstack">
                <interceptor-ref name="myinterceptor" />
                <interceptor-ref name="secinterceptor" />
            </interceptor-stack>
        </interceptors>
        <action name="hello" class="com.owlforest.home.action.HelloWorldAction"
                method="excute">
            <interceptor-ref name="myinterceptorstack"/>
            <interceptor-ref name="params"/>
            <result name="success">/HelloWorld.jsp</result>
        </action>
    </package>
</struts>

5、因为拦截器和拦截器栈是在package中声明使用的,作用域仅在当前声明的package中,对于一些验证、异常相关的拦截器,需要在全局、也就是所有的package中都能使用,这种需要定义一个全局的package,使相应的action对应的package继承自该全局package即可。如下:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
        "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <!-- 设置struts是否为开发模式,默认为false,测试阶段一般设为true. -->
    <constant name="struts.devMode" value="true"/>
    <!--全局的package-->
    <package name="commominterceptor" extends="struts-default">
        <interceptors>
            <interceptor name="myinterceptor"
                         class="com.owlforest.home.interceptor.MyInterceptor" />
            <interceptor name="secinterceptor"
                         class="com.owlforest.home.interceptor.SecInterceptor" />
            <interceptor-stack name="myinterceptorstack">
                <interceptor-ref name="myinterceptor" />
                <interceptor-ref name="secinterceptor" />
            </interceptor-stack>
        </interceptors>
    </package>
    <!--继承自commominterceptor的package-->
    <package name="suibian" extends="commominterceptor">
        <action name="hello" class="com.owlforest.home.action.HelloWorldAction"
                method="excute">
            <interceptor-ref name="myinterceptorstack"/>
            <interceptor-ref name="params"/>
            <result name="success">/HelloWorld.jsp</result>
        </action>
    </package>
</struts>

拦截器栈与全局拦截器的运行效果如下:

Struts2学习:interceptor(拦截器)的使用