一、环境准备

准备一个项目，项目中有3个模块，1

1. FeignClient（下图的goods-center）

2. FeignApi(下图的user-api) ，这个模块为其他2个模块的公共依赖模块，相当于2个项目通信的协议

3. FeignServer (下图的user-center)

二、 user-api 模块编写

1. pom.xml 文件关键点

<dependencies>
		<!--	次项目中包含VO对象,为了节约开发成本，引入lombok	-->
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<version>RELEASE</version>
			<scope>compile</scope>
		</dependency>

		<!--	因为需要在 api interface中写RequestMapping 故需要引入web包	-->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<!--	openfeign 不用多说了	-->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
		</dependency>

		<!--	没有loadbalancer调用会报错	-->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-loadbalancer</artifactId>
		</dependency>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<!--		这个工程没有main方法，所以只需要普通打包即可		-->
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-jar-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

2. UserCenterFacade 

 因为目前还有集成注册中心，故只能在@FeignClient 中指定服务端的地址 http://localhost:9521

package com.ychen.usercenter.api;

import com.ychen.usercenter.vo.UserInfoVo;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;


@FeignClient(name = "user-center", url = "http://localhost:9521")
public interface UserCenterFacade {
    @RequestMapping(value = "/getUserInfo/ByUserId")
    UserInfoVo getUserInfoByUserId(Long userId);
}

3. UserInfoVo

package com.ychen.usercenter.vo;

import lombok.Data;

@Data
public class UserInfoVo {
    private Long userId;
    private String nickName;
    private Integer age;
}

三、user-center 模块编写

1. pom.xml 文件关键点

将user-api 模块依赖进来即可

	<dependencies>
		<dependency>
			<groupId>com.ychen</groupId>
			<artifactId>user-api</artifactId>
			<version>0.0.1-SNAPSHOT</version>
		</dependency>
	</dependencies>

2. UserCenterController

package com.ychen.usercenter.controllers;

import com.ychen.usercenter.api.UserCenterFacade;
import com.ychen.usercenter.vo.UserInfoVo;
import org.springframework.web.bind.annotation.RestController;


@RestController
public class UserCenterController implements UserCenterFacade {
    @Override
    public UserInfoVo getUserInfoByUserId(Long userId) {
        UserInfoVo userInfo = new UserInfoVo();
        userInfo.setAge(22);
        userInfo.setNickName("张三");
        userInfo.setUserId(3323323258122L);
        return userInfo;
    }
}

3. 配置文件application.properties

server.port=9521
spring.application.name=user-center

四、goods-center模块编写

1. GoodsController

package com.ychen.goodscenter.controllers;

import com.ychen.usercenter.api.UserCenterFacade;
import com.ychen.usercenter.vo.UserInfoVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GoodsController {
    @Autowired
    private UserCenterFacade userCenterFacade;

    @GetMapping("/getGoodsDetails")
    public String getGoodsDetails(@RequestParam(value = "goodsId") Long goodsId) {
        UserInfoVo userInfo = userCenterFacade.getUserInfoByUserId(2222L);
        return String.format("Hello %s!", userInfo.toString());
    }

}

2. GoodsCenterApplication

package com.ychen.goodscenter;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;


@SpringBootApplication
@EnableFeignClients(basePackages = "com.ychen.**")
public class GoodsCenterApplication {

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

}

这里要注意@EnableFeignClients(basePackages = "com.ychen.**") ，因为com.ychen.usercenter.api.UserCenterFacade属于引用外部项目，所以这里要指定扫描包路径，否则Spring默认不会扫工程以外的包

五、版本管理

这里要注意一个点，SpringBoot3.1.7 对于的SpringCloud 版本是2022.0.3~2023.0.0 之间，版本错误也会导致项目起不来

以下是主工程的pom.xml 部分配置

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <java.version>17</java.version>
        <spring-cloud.version>2022.0.4</spring-cloud.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>