基本步骤

1. 创建controller

package com.hzc.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
@RequestMapping("/student")
public class StudentController {
    @RequestMapping("/show")
    @ResponseBody
    public String show(){
        return "interceptor...";
    }

    @RequestMapping("/login")
    public String login(Model model, String username){
        model.addAttribute("username",username);
        return "index";
    }
}

2. 自定义拦截器类，实现HandlerInterceptor接口。

package com.hzc.interceptor;

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

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

public class StudentInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String username = (String) request.getSession().getAttribute("username");
        if(username == null){
            response.getWriter().write("username is null");
            return false;
        }
        return true;

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}

3. 注册拦截器，创建一个拦截器核心配置类并继承WebMvcConfigurer

package com.hzc.config;

import com.hzc.interceptor.StudentInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    //拦截的方法
    String[] pathPattern = {"/student/show"};
    //不拦截的方法
    String[] excludePathPattern = {"/student/login"};
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new StudentInterceptor())
                .addPathPatterns(pathPattern)
                .excludePathPatterns(excludePathPattern);
    }
}

4.测试。

springBoot拦截器