SSM项目中使用拦截器和过滤器的实现示例

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;

//拦截器
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //获取请求的URL
        String requestURI=request.getRequestURI();
        HttpSession session=request.getSession();
        Object userInfo=request.getSession().getAttribute("USERINFO");
        System.out.println("链接:"+requestURI+"进入拦截器");
        if(userInfo==null){ //表示未登录就想进入系统
            //直接重定向到登录界面
            String serverPath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/index.jsp";
            response.sendRedirect(serverPath);
            return false;
        }else{
            //登陆成功，不拦截
            return true;
        }

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("跳转后拦截");
    }

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

<!--拦截器配置-->
	<mvc:interceptors>
		<!--后台访问拦截器-->
		<mvc:interceptor>
			<!--拦截所有资源-->
			<mvc:mapping path="/**"/>
			<!--登陆不拦截-->
			<mvc:exclude-mapping path="/user/login"/>
			<!--邮箱激活不拦截-->
			<mvc:exclude-mapping path="/user/activeEmail"/>
			<!--静态资源的目录不拦截-->
			<mvc:exclude-mapping path="/commons/**"/>
			<!--用户通过邮箱中重置密码的链接不拦截-->
			<mvc:exclude-mapping path="/email/resetPassword"/>
			<!--激活邮箱的验证不拦截-->
			<mvc:exclude-mapping path="/user/validateCode"/>
			<!--实现拦截功能的类-->
			<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;

//自定义过滤器
public class LoginFilter implements Filter {
    //初始化方法
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
     //初始化处理
        System.out.println("过滤器初始化");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //过滤处理
        //servletRequest 是个接口，HttpServletRequest 是实现，但是有些方法是HttpServletRequest独有的，如：getSession
        //HttpServletRequest接口是继承servletRequest接口，增加了和http相关的方法
        HttpServletRequest request= (HttpServletRequest) servletRequest;
        HttpServletResponse response= (HttpServletResponse) servletResponse;
//        String requestURI=request.getRequestURI();
//        System.out.println("链接:"+requestURI+"进入过滤器");
        HttpSession session=request.getSession();
        if(session.getAttribute("USERINFO")==null){
            //非法请求，直接跳转到登陆界面
            String serverPath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/index.jsp";
            response.sendRedirect(serverPath);
        }else{
            //正常登录，放行
            filterChain.doFilter(request,response);
        }
    }

    @Override
    public void destroy() {
     //释放资源
        System.out.println("过滤器销毁");
    }
}

<!--使用过滤器实现登陆控制-->
  <!--filter标签用于声明过滤器对象-->
  <filter>
    <!--过滤器名称-->
    <filter-name>LoginFilter</filter-name>
    <!--过滤器完整类名-->
    <filter-class>com.ssm.Filter.LoginFilter</filter-class>
  </filter>
  <!--filter-mapping用于创建过滤器的映射，指定Web应用中，哪些URL应用哪一个过滤器进行处理-->
  <filter-mapping>
    <filter-name>LoginFilter</filter-name>
    <!--url-pattern用于指定过滤器应用的URL-->
    <!--过滤的页面(自定义),这里对登录界面就不要过滤了-->
    <url-pattern>/views/*</url-pattern>
  </filter-mapping>