一、新建springboot工程

二、添加实体类

@Data
@AllArgsConstructor
public class User {
    private Integer id;
    private String name;
    private Integer age;
}

三、创建拦截器类

创建拦截器类,实现HandlerInterceptor接口,重写preHandle方法,在该方法中编写业务拦截的规则

public class UserInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //从session中获取user的信息
        User user =(User)request.getSession().getAttribute("user");
        //判断用户是否登录
        if (null==user){
            response.sendRedirect(request.getContextPath()+"/user/error");
            return false;
        }
        return true;
    }
}

四、创建拦截器配置类

使用@Configuration注解将这个类定义为配置类,实现WebMvcConfigurer接口并且重写addInterceptors方法

@Configuration//定义此类为配置类
public class InterceptorConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    	//addPathPatterns拦截的路径
        String[] addPathPatterns = {
                "/user/**"
        };
        //excludePathPatterns排除的路径
        String[] excludePathPatterns = {
                "/user/login","/user/noLg","/user/error"
        };
        //创建用户拦截器对象并指定其拦截的路径和排除的路径
        registry.addInterceptor(new UserInterceptor()).addPathPatterns(addPathPatterns).excludePathPatterns(excludePathPatterns);
    }
}

五、编写Controller类

@RestController
@RequestMapping("/user")
public class MyController {
    //用户登录
    @RequestMapping("login")
    public Object login(HttpServletRequest request){
        //将已经登录的用户信息添加到session中
        request.getSession().setAttribute("user",new User(1,"张三",20));
        return "Login Success";
    }
    //不需要登录也能访问的请求
    @RequestMapping("/noLg")
    public Object noLg(){
        return "Everyone Can See";
    }
    //必须要登录才能访问的请求
    @RequestMapping("/mustLg")
    public Object mustLg(){
        return "Only User Can See";
    }
    //如果用户未登录访问了需要登录才能访问的请求会跳转到这个错误提示页面
    @RequestMapping("/error")
    public Object error(){
        return "You Must Login";
    }
}