使用拦截器验证用户访问权限

Using Interceptor to validate user access privilege(使用拦截器验证用户访问权限)

问题描述

我正在尝试使用 Interceptor 来限制用户执行某些操作.

I am trying to use an Interceptor to restrict users from performing certain actions.

ContainsKeyInterceptor:

public class ContainsKeyInterceptor extends AbstractInterceptor implements SessionAware {
    private static final long serialVersionUID = 1L;

    private Map<String, Object> session;

    @Override
    public String intercept(ActionInvocation actionInvocation) throws Exception {
        if(session == null) {
            System.out.println("session is null");
        }

        if(session.containsKey("currentId")) {
            return "index";
        }

        String result = actionInvocation.invoke();

        return result;
    }

    @Override
    public void setSession(Map<String, Object> session) {
        this.session = session;
    }
}

如果在 session 中找到 currentId，则应该将用户重定向到索引页面.

It is supposed to redirect the user to the index page if currentId is found in the session.

但是，我得到一个 NullPointerException，说 session 为空，由 if-check 验证.

However, I am getting a NullPointerException, saying session is null, as verified by the if-check.

struts.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>
    <constant name="struts.devMode" value="false" />

    <!-- actions available to guests -->
    <package name="guest" extends="struts-default">
        <interceptors>
            <interceptor name="containskeyinterceptor" class="com.mypackage.interceptor.ContainsKeyInterceptor" />
        </interceptors>

        <action name="index" class="com.mypackage.action.IndexAction">
            <interceptor-ref name="containskeyinterceptor" />
            <result type="redirect">/index.jsp</result>
            <result name="index" type="redirect">/index.jsp</result>
        </action>

        <action name="login" class="com.mypackage.action.LoginAction">
            <interceptor-ref name="containskeyinterceptor" />
            <result type="redirect">/index.jsp</result>
            <result name="input">/login.jsp</result>
            <result name="index" type="redirect">/index.jsp</result>
        </action>       
    </package>

    <!-- actions available to members -->
    <package name="member" extends="struts-default">
        <action name="logout" class="com.mypackage.action.LogoutAction">
            <result type="redirectAction">
                <param name="actionName">index</param>
            </result>
        </action>
    </package>
</struts>

为什么session为空，如何解决?

Why is the session null and how to resolve?

(这个是我使用的参考.)

推荐答案

Struts Session 只是一个包装底层 HttpSession 的 Map.

Struts Session is just a Map<String,Object> wrapping the underlying HttpSession.

在实现 SessionAware 接口时 是在 Action 中获取它的正确方法，如果您想从在拦截器中，您需要执行以下操作:

While implementing the SessionAware interface is the correct way to get it in an Action, if you want to get it from within an Interceptor, you need to do the following:

获取 Struts Session Map:

To get the Struts Session Map:

@Override
public String intercept(ActionInvocation ai) throws Exception {
    final ActionContext context = ai.getInvocationContext();

    // Struts Session
    Map<String, Object> session = context.getSession();

获取真正的HttpSession对象:

@Override
public String intercept(ActionInvocation ai) throws Exception {
    final ActionContext context = ai.getInvocationContext();

    HttpServletRequest request = (HttpServletRequest)context.get(StrutsStatics.HTTP_REQUEST);

    // Http Session
    HttpSession session = request.getSession();

也就是说，您在操作中没有获得会话(也没有任何其他参数、对象等)的原因是您犯了一个常见错误:只应用一个拦截器(你的)而不是应用整个拦截器堆栈(应该包含你的):

That said, the reason you are not getting session (nor any other parameter, object and so on) in your Actions, is because you are falling in a common mistake: applying only one Interceptor (your) instead of applying an entire Interceptor Stack (that should contain your):

你可以在每个动作中定义两次:

You can define it twice in every action:

<action name="login" class="ph.edu.iacademy.action.LoginAction">
    <interceptor-ref name="defaultStack" /> <!-- this is missing -->
    <interceptor-ref name="containskeyinterceptor" />

或者，更好的是，在自定义堆栈中定义一次，并始终使用堆栈:

or, much better, define it once in a custom stack, and use always the stack:

<interceptors>
    <interceptor-stack name="yourStack">                
       <interceptor-ref name="defaultStack"/>
       <interceptor-ref name="containskeyinterceptor"/>
    </interceptor-stack>
</interceptors>

<action name="login" class="ph.edu.iacademy.action.LoginAction">
    <interceptor-ref name="yourStack" />

并最终使用 default-interceptor-ref 定义它以避免为该包的每个操作配置编写它:

and eventually define it with default-interceptor-ref to avoid writing it for every action config of that package:

<default-interceptor-ref name="yourStack"/>

<action name="login" class="ph.edu.iacademy.action.LoginAction">

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