SpringBoot如何添加拦截器

在web开发的过程中，为了实现登录权限验证，我们往往需要添加一个拦截器在用户的的请求到达controller层的时候实现登录验证，那么SpringBoot如何添加拦截器呢？

步骤如下：

1.继承WebMvcConfigureAdapter类，覆盖其addInterceptors接口,注册我们自定义的拦截器：

/** 
 * 
 * 注册拦截器 
 * Created by SYSTEM on 2017/8/16. 
 */  
public class WebAppConfig extends WebMvcConfigurerAdapter {  
  
    @Override  
    public void addInterceptors(InterceptorRegistry registry) {  
        //注册自定义拦截器，添加拦截路径和排除拦截路径  
        registry.addInterceptor(new InterceptorConfig()).addPathPatterns("api/path/**").excludePathPatterns("api/path/login");  
    }  
} 

2.实现HandlerInterceptor接口，重写接口中的三个方法：

public class InterceptorConfig  implements HandlerInterceptor{  
  
    private static final Logger log = LoggerFactory.getLogger(InterceptorConfig.class);  
  
    /** 
     * 进入controller层之前拦截请求 
     * @param httpServletRequest 
     * @param httpServletResponse 
     * @param o 
     * @return 
     * @throws Exception 
     */  
    @Override  
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {  
  
        log.info("---------------------开始进入请求地址拦截----------------------------");  
        HttpSession session = httpServletRequest.getSession();  
        if(!StringUtils.isEmpty(session.getAttribute("userName"))){  
            return true;  
        }  
        else{  
            PrintWriter printWriter = httpServletResponse.getWriter();  
            printWriter.write("{code:0,message:\"session is invalid,please login again!\"}");  
            return false;  
        }  
  
    }  
  
    @Override  
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {  
        log.info("--------------处理请求完成后视图渲染之前的处理操作---------------");  
    }  
  
    @Override  
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {  
        log.info("---------------视图渲染之后的操作-------------------------0");  
    }  
}  

这样我们就可以在用户请求到达controller层实现登录拦截了，所有用户请求都会被拦截，在prehandle方法进行登录判断，返回true则验证通过，否则失败