package com.ssm.Interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

//攔截器
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //獲取請(qǐng)求的URL
        String requestURI=request.getRequestURI();
        HttpSession session=request.getSession();
        Object userInfo=request.getSession().getAttribute("USERINFO");
        System.out.println("鏈接:"+requestURI+"進(jìn)入攔截器");
        if(userInfo==null){ //表示未登錄就想進(jìn)入系統(tǒng)
            //直接重定向到登錄界面
            String serverPath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/index.jsp";
            response.sendRedirect(serverPath);
            return false;
        }else{
            //登陸成功，不攔截
            return true;
        }

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("跳轉(zhuǎn)后攔截");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("渲染后攔截");
    }
}

<!--攔截器配置-->
	<mvc:interceptors>
		<!--后臺(tái)訪問攔截器-->
		<mvc:interceptor>
			<!--攔截所有資源-->
			<mvc:mapping path="/**"/>
			<!--登陸不攔截-->
			<mvc:exclude-mapping path="/user/login"/>
			<!--郵箱激活不攔截-->
			<mvc:exclude-mapping path="/user/activeEmail"/>
			<!--靜態(tài)資源的目錄不攔截-->
			<mvc:exclude-mapping path="/commons/**"/>
			<!--用戶通過郵箱中重置密碼的鏈接不攔截-->
			<mvc:exclude-mapping path="/email/resetPassword"/>
			<!--激活郵箱的驗(yàn)證不攔截-->
			<mvc:exclude-mapping path="/user/validateCode"/>
			<!--實(shí)現(xiàn)攔截功能的類-->
			<bean class="com.ssm.Interceptor.LoginInterceptor"></bean>
		</mvc:interceptor>
	</mvc:interceptors>

package com.ssm.Filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

//自定義過濾器
public class LoginFilter implements Filter {
    //初始化方法
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
     //初始化處理
        System.out.println("過濾器初始化");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //過濾處理
        //servletRequest 是個(gè)接口，HttpServletRequest 是實(shí)現(xiàn)，但是有些方法是HttpServletRequest獨(dú)有的，如：getSession
        //HttpServletRequest接口是繼承servletRequest接口，增加了和http相關(guān)的方法
        HttpServletRequest request= (HttpServletRequest) servletRequest;
        HttpServletResponse response= (HttpServletResponse) servletResponse;
//        String requestURI=request.getRequestURI();
//        System.out.println("鏈接:"+requestURI+"進(jìn)入過濾器");
        HttpSession session=request.getSession();
        if(session.getAttribute("USERINFO")==null){
            //非法請(qǐng)求，直接跳轉(zhuǎn)到登陸界面
            String serverPath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/index.jsp";
            response.sendRedirect(serverPath);
        }else{
            //正常登錄，放行
            filterChain.doFilter(request,response);
        }
    }

    @Override
    public void destroy() {
     //釋放資源
        System.out.println("過濾器銷毀");
    }
}

<!--使用過濾器實(shí)現(xiàn)登陸控制-->
  <!--filter標(biāo)簽用于聲明過濾器對(duì)象-->
  <filter>
    <!--過濾器名稱-->
    <filter-name>LoginFilter</filter-name>
    <!--過濾器完整類名-->
    <filter-class>com.ssm.Filter.LoginFilter</filter-class>
  </filter>
  <!--filter-mapping用于創(chuàng)建過濾器的映射，指定Web應(yīng)用中，哪些URL應(yīng)用哪一個(gè)過濾器進(jìn)行處理-->
  <filter-mapping>
    <filter-name>LoginFilter</filter-name>
    <!--url-pattern用于指定過濾器應(yīng)用的URL-->
    <!--過濾的頁(yè)面(自定義),這里對(duì)登錄界面就不要過濾了-->
    <url-pattern>/views/*</url-pattern>
  </filter-mapping>