什么是攔截器，SpringBoot-攔截器

1.寫一個攔截器
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;import com.alibaba.fastjson.JSONObject;public class Interceptor extends HandlerInterceptorAdapter {@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {if(從request中獲取的參數不合法){sendFailResult(response,"參數不合法" );return false;}elsereturn true;}}}private void sendFailResult(HttpServletResponse response, String resultMessage) {JSONObject reObj = new JSONObject();reObj.put("resultMessage", resultMessage);             response.setContentType("application/json;charset=UTF-8");response.setHeader("Cache-Control", "no-cache");try {response.getWriter().write(reObj.toString());} catch (Exception e) {Syso("PHP是最好的語言");}}
}
2.定義哪些URL路徑需要攔截，需要再寫一個配置類，用來加載上邊的類
@Configuration//新版本已經表示WebMvcConfigurerAdapter過時，取而代之的是WebMvcConfigurationSupport
public class InterceptorConfig extends WebMvcConfigurerAdapter {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new Interceptor()).addPathPatterns("/**");//**表示攔截所有路徑}
}