1、在消费端的项目中引入openfeign依赖

首先需要确保引入了springcloud，因为openfeign依赖与springcloud

在消费端的pom.xml中引入openfeign，父项目中已经引入了springcloud了

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springalibabanew</artifactId>
        <groupId>com.chinasofti</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>order-openfeign</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--nacos-服务注册发现-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--添加openfeign依赖-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>
</project>

父项目的pom.xml已经引入了springcloud

2、添加openfeign接口和方法

openfeign是解决服务之间调用的，我们之前在订单中调用库存的服务了，我们尽量让feign的名字和库存的服务的名字保持一致，这样方便使用，同样的方法也用controller中的方法，controller中怎么定义的这边就怎么调用，比如原先的StockController

package com.chinasofti.stock.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Author mxx
 * @Date 2023/6/12 16:48
 * @Version 1.0
 */
@RestController
@RequestMapping("/stock")
public class StockController {
    @Value("${server.port}")
    String port;
    @RequestMapping("/reduct")
    public String reduct(){
        System.out.println("扣减库存");
        return "扣减库存:"+port;
    }
}

对应的openfeign接口如下：

package com.chinasofti.order.feign;

/**
 * @Author mxx
 * @Date 2023/6/15 11:00
 * @Version 1.0
 */

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

/**
 * name指定调用rest接口所对应的服务名
 * path指定调用rest接口所在的StockController指定的RequestMapping
 */
@FeignClient(name="stock-service",path="/stock")
public interface StockFeignService {
    //声明需要调用的rest接口对应的方法，将原先的StockController中的方法复制过来
    @RequestMapping("/reduct")
    String reduct();
}

3、客户端调用代码修改

原先使用了restTemplate，现在将这个删除掉

将创建的feign注入到OrderController中，然后调用里面的方法，如下：

package com.chinasofti.order.controller;

import com.chinasofti.order.feign.StockFeignService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @Author mxx
 * @Date 2023/6/12 16:44
 * @Version 1.0
 */
@RestController
@RequestMapping("/order")
public class OrderController {
    @Autowired
    StockFeignService stockFeignService;
    @RequestMapping("/add")
    public String add(){
        System.out.println("下单成功");
        String msg = stockFeignService.reduct();
        return "Hello Feign!"+msg;
    }
}

但是这样stockFeignService下边有个波浪线，如下

我们需要在启动类中加入@EnableFeignClients注解，如下：

package com.chinasofti.order;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * @Author mxx
 * @Date 2023/6/12 16:55
 * @Version 1.0
 */
@SpringBootApplication
@EnableFeignClients
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class,args);
    }
}

这样那个波浪线就消失了。修改端口为8040，然后启动订单和stock服务