示例：A服務呼叫B服務

AB服務中新增feign+redis+session依賴

//feign依賴
<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
//redis-session依賴
<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
        <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>
</dependency>    

1.A服務

Application啟動類中新增

import feign.RequestInterceptor;
import feign.RequestTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
 
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.session.FlushMode;
import org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession;
 
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;

@SpringBootApplication
@EnableEurekaClient
//增加redissession快取支援
@EnableRedisHttpSession(flushMode = FlushMode.IMMEDIATE)
@MapperScan({"com.**.dao"})
//增加feign支援，引入feign註解，feign掃描路徑可以單獨指定(basePackages = ),預設是spring的掃描路徑
@EnableFeignClients(basePackages = "com.**.feign")
public class SyhCloudXxkglApplication extends SpringBootServletInitializer implements RequestInterceptor {

    public static void main(String[] args) {
        SpringApplication.run(SyhCloudXxkglApplication.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(SyhCloudXxkglApplication.class);
    }

    /*使用Feign呼叫某個遠端API，這個遠端API需要傳遞一個鑑權資訊，我們可以把cookie裡面的session資訊放到Header裡面，這個Header是動態的，跟你的HttpRequest相關，我們選擇編寫一個攔截器來實現Header的傳遞，也就是需要實現RequestInterceptor介面*/
    @Override
    public void apply(RequestTemplate template) {

        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        if (requestAttributes == null) {
            return;
        }

        HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();
        Enumeration<String> headerNames = request.getHeaderNames();
        if (headerNames != null) {
            while (headerNames.hasMoreElements()) {
                String name = headerNames.nextElement();
                Enumeration<String> values = request.getHeaders(name);
                while (values.hasMoreElements()) {
                    String value = values.nextElement();
                    template.header(name, value);
                }
            }
        }

    }
}

建立一個包，存放呼叫其他服務的介面檔案

package com.**.feign;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * @Title:
 * @ProjectName
 * @Description: TODO
 * @author: TongSiYu
 * @date 2021-8-9 14:55
 */
/*指定需要呼叫的B服務名稱*/
@FeignClient("syh-cloud-system")
public interface Rose {
    /*需要訪問的完整路徑*/
    @RequestMapping("/role/queryAllForRole")
    public Object getRose();
}

呼叫介面

package com.**.controller;

import com.**.feign.Rose;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;

/**
 * @Title:
 * @ProjectName
 * @Description: TODO
 * @author: TongSiYu
 * @date 2021-8-9 14:53
 */
@RestController
@RequestMapping("/feign")
public class FeignController {
    /*注入B服務的介面檔案*/
    @Autowired
    private Rose rose;

    @RequestMapping("/getrose")
    public Object getProductInfoList(HttpServletRequest request)     {
        System.out.println("1");
        Object object = rose.getRose();
        return object;
    }
}