SpringBoot2.X新版本配置攔截器在項目中的使用

攔截器：和過濾器用途基本類似

SpringBoot2.X新版本配置攔截器 implements WebMvcConfigure

• 自定義攔截器 HandlerInterceptor
  • preHandle：調用Controller某個方法之前
  • postHandle：Controller之后調用，視圖渲染之前，如果控制器Controller出現了異常，則不會執行此方法
  • afterCompletion：不管有沒有異常，這個afterCompletion都會被調用，用於資源清理
• 按照注冊順序進行攔截，先注冊，先被攔截

攔截不生效常見問題

1. 是否有加@Configuration
2. 攔截路徑是否有問題 **和*
3. 攔截器最后路徑一定要 /** 如果是目錄的話則是 /*/

場景：權限控制、用戶登陸狀態控制等

和Filter過濾器的區別

Filter和Interceptor二者都是AOP編程思想的體現，功能基本都可以實現
攔截器功能更強大些，Filter能做的事情它都能做
Filter在只在Servlet前后起作用，而Interceptor能夠深入到方法前后、異常拋出前后等
依賴於Servlet容器既web應用中，而Interceptor不依賴於Servlet容器所以可以運行在多種環境
在接口調用的生命周期，Interceptor可以被多次調用，而Filter只能在容器初始化時調用一次。
Filter和Interceptor的執行順序
過濾前->攔截前->action執行->攔截后->過濾后

CustomWebMvcConfigure.java

package net.cyb.demo.interceptor;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * 攔截器配置類
 */
@Configuration
public class CustomWebMvcConfigure implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(getLoginInterceptor()).addPathPatterns("/api/v1/pri/**");
        WebMvcConfigurer.super.addInterceptors(registry);
    }
    @Bean
    public LoginIntercepter getLoginInterceptor(){
        return new LoginIntercepter();
    }
}

LoginIntercepter.java

package net.cyb.demo.interceptor;

import com.fasterxml.jackson.databind.ObjectMapper;
import net.cyb.demo.domain.User;
import net.cyb.demo.service.impl.UserServiceImpl;
import net.cyb.demo.utils.JsonData;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import org.thymeleaf.util.StringUtils;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;

public class LoginIntercepter implements HandlerInterceptor {
    private static final ObjectMapper objectMapper=new ObjectMapper();
    private void renderJson(HttpServletResponse response,String json){
        response.setCharacterEncoding("utf-8");
        response.setContentType("application/json");
        try{
            PrintWriter writer=response.getWriter();
            writer.print(json);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    @Override
    public boolean preHandle(HttpServletRequest req, HttpServletResponse resp, Object handler) throws Exception {
        System.out.println("LoginIntercepter preHandle==========");
        String token = req.getHeader("token");
        if (StringUtils.isEmpty(token)) {
            token = req.getParameter("token");
        }
        if (StringUtils.isEmpty(token)) {
            JsonData jsonData=JsonData.buildError(-3,"未登陸");
            String jsonStr=objectMapper.writeValueAsString(jsonData);
            renderJson(resp, jsonStr);
            return false;
        } else {
            //判斷token是否合法 TODO
            User user = UserServiceImpl.sessionMap.get(token);
            if (user != null) {
                return true;
            }else {
                JsonData jsonData=JsonData.buildError(-2,"登陸失敗,token無效");
                String jsonStr=objectMapper.writeValueAsString(jsonData);
                renderJson(resp, jsonStr);
                return false;
            }
        }
    }

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

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("LoginIntercepter afterCompletion==========");
        HandlerInterceptor.super.afterCompletion(request,response,handler,ex);
    }
}