Simple example of SpringMVC's interceptor filter

filter

The filter is actually the content in the servlet, which can be used in many places and
needs to be configured in web.xml

    <filter>
        <filter-name>tokenFilter</filter-name>
        <filter-class>com.wpp.filter.TokenFilter</filter-class>
        <init-param>
            <param-name>allowedMethods</param-name>
            <param-value>GET,POST</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>tokenFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

Code implementation: The basic logic is to implement the interface in the servlet of Filter, rewrite the doFilter code, and execute chain.doFilter(request, response) if the filtering is successful; this means to execute the next filter

package com.wpp.filter;

import org.springframework.stereotype.Component;

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

@Component
public class TokenFilter implements Filter {
    
    
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    
    
        System.out.println("初始化"+this.getClass());
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    
    
        HttpServletRequest req = (HttpServletRequest) request;
        System.out.println("经过过滤器");
        System.out.println(req.getSession().getId());
        System.out.println(req.getSession().getAttribute("admin"));
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
    
    
        System.out.println("销毁"+this.getClass());
    }
}

interceptor

The interceptor here is the content in SpringMVC, which needs to implement the HandlerInceptor interface
java code

package com.wpp.interceptor;

import org.springframework.stereotype.Component;
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;


public class LoginInterceptor implements HandlerInterceptor {
    
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    
    
        System.out.println("MyInterceptor 拦截器执行postHandle()方法");
        HttpSession session = request.getSession();
        // 检查用户是否已登录
        if (session.getAttribute("admin") == null) {
    
    
            // 用户未登录，重定向到登录页面或返回错误信息
            response.sendRedirect(request.getContextPath() + "/");
            return false;
        }

        // 用户已登录，允许继续访问
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    
    
        System.out.println("MyInterceptor 拦截器执行afterCompletion方法");
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    
    
        System.out.println("MyInterceptor 拦截器执行postHandle()方法");
    }
}

Because it is in Spring, this needs to be configured in the spring xml configuration file

    <!-- 配置拦截器 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <!-- 配置拦截器作用的路径 -->
            <mvc:mapping path="/**" />
            <!-- 配置不需要拦截作用的路径 -->
            <mvc:exclude-mapping path="/login" />
            <!-- 定义<mvc:interceptor>元素中，表示匹配指定路径的请求才进行拦截 -->
            <bean class="com.wpp.interceptor.LoginInterceptor" />
        </mvc:interceptor>
   </mvc:interceptors>

There is another way to configure annotations, the basic implementation is

package com.wpp.config;


import com.wpp.interceptor.GlobalInceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class MyWebMvcConfig implements WebMvcConfigurer {
    
    

    @Autowired
    GlobalInceptor globalInceptor;
    /**
     * 将自定义拦截器作为bean写入配置
     * @return
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    
    

        //拦截处理操作的匹配路径
        //放开静态拦截
        registry.addInterceptor(globalInceptor)
                //拦截所有路径
                .addPathPatterns("/**")
                //排除路径
                .excludePathPatterns("/login", "/exit", "/get_cpacha")
                //排除静态资源拦截
                .excludePathPatterns("/xadmin/**");

    }

}