关于Spring Portlet开发中的HandlerInterceptor

 在Spring Portlet开发中，我们可以用HandlerInterceptor 来实现对于portlet的拦截，主要的需求场景比如授权处理。它可以让我们来自定义处理器执行链。

其实很类似Web开发中的Filter,但是不同的在于Filter是Servlet范畴的概念，它可以用来操作ServletRequest 和ServletResponse，并且配置在web.xml中，而Portlet HandlerInterceptor是Portlet范畴的概念，它可以用来操作PortletRequest和PortletResponse，并且配置在Spring应用上下文中。

在HandlerInterceptor中定义了若干主要方法：具体参见

http://supercharles888.blog.51cto.com/609344/845170

 

为了让我们的应用使用HandlerInterceptor，一个常见的设计模式是使用Adaptor模式，让我们的自定义HandlerInterceptor类继承自HandlerInterceptorAdaptor类，然后进行覆写。 下面是个例子.

 

例子：

a.需求，我们需要在Portlet的任何页面上都可以用到当前登录的用户的用户名和所属权限，那么我们的可以开发一个HandlerInterceptor:

/**
 *
 * This handler interceptor will intercept the request before/after the flow.
 * Since it is configured in envprovisioning-config.xml ,so it will intercept request to envprovision flow
 * We can have some pre/post handling work such as initialize the variables
 *@author cwang58
 *@created date: Feb 5, 2013
 */
public class EnvProvisionHandlerInterceptor extends HandlerInterceptorAdapter {

    private static final SimpleLogger LOGGER = new SimpleLogger(EnvProvisionHandlerInterceptor.class);


    /**
     * This method will pre handle before rendering the first page in the flow
     * Here it get the current logined user information from the ThemeDisplay
     * Then get the role that this user belongs to ,we make sure whether this user belongs to AER Admin-AERAdmin
     * if user belongs to this ,then set isAdministrator attribute to request scope so that it can be used in every page of this flow.
     */
    @Override
    public boolean preHandleRender(RenderRequest request,
            RenderResponse response, Object handler)  {
        User user = EnvProUtil.getUserObj(request);

        if(user == null){
            return false;
        }
        String userName= user.getScreenName();
        LOGGER.debug("Login user name:"+userName);

        boolean isAdministrator = false;

        try{

        List<Role> roles = user.getRoles();
        for(int i= 0;i<roles.size();i++) {

            Role role =roles.get(i);
            if("AER Admin-AERAdmin".equals(role.getName()) || "Administrator".equals(role.getName())){
                isAdministrator=true;
                LOGGER.debug("Login user has role:"+role.getName());
                break;
            }
        }


        request.setAttribute("userId", userName);
        request.setAttribute("isAdministrator", isAdministrator);

        return true;

        }catch(SystemException ex){
            LOGGER.error("SystemException occurs when get current user role",ex);
            return false;
        }
    }






}

比如以上的例子中，我们从ThemeDisplay中获取当前用户的权限和用户名，然后把它设置到RenderRequest的request scope上。

 

为了让这个HandlerInterceptor生效，我们必须配置这个interceptor在Spring应用上下文中：

<bean id="portletModeHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeHandlerMapping">
        <property name="portletModeMap">
            <map>
                <entry key="view">
                    <bean class="xx.xx.xx.envprovisioning.handlers.EnvProvisionFlowHandler" />
                </entry>
            </map>
        </property>
        <property name="interceptors">
            <list>
                <ref bean="envprovisionhandlerinterceptor"/>
            </list>
        </property>
    </bean>
    <!-- add interceptor to get user and privilege -->
    <bean id="envprovisionhandlerinterceptor" class="xx.xx.xx.envprovisioning.interceptors.EnvProvisionHandlerInterceptor"/>

这样，页面上就可以用el表达式来获取这些信息了。