关于微服务基本框架搭建--fegin最小使用demo

1. 整体目录结构

microservice-demo（父工程） ├── pom.xml（父POM，管理版本） ├── common（公共模块） │ ├── pom.xml │ └── src/main/java/com/demo/common/ │ ├── dto/User.java │ └── api/UserApi.java ├── service-b（服务提供方，端口8081） │ ├── pom.xml │ ├── src/main/java/com/demo/serviceb/ │ │ ├── ServiceBApplication.java │ │ └── controller/UserController.java │ └── src/main/resources/application.yml └── service-a（服务调用方，端口8080） ├── pom.xml ├── src/main/java/com/demo/servicea/ │ ├── ServiceAApplication.java │ └── controller/OrderController.java └── src/main/resources/application.yml

2. 父工程 pom.xml（根目录）

<?xml version="1.0" encoding="UTF-8"?><projectxmlns="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"><modelVersion>4.0.0</modelVersion><groupId>com.demo</groupId><artifactId>microservice-demo</artifactId><version>1.0.0</version><packaging>pom</packaging><!-- 引入 Spring Boot 父依赖，统一版本 --><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.7.14</version><relativePath/></parent><!-- 管理 Spring Cloud 版本 --><properties><java.version>8</java.version><spring-cloud.version>2021.0.8</spring-cloud.version></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><modules><module>common</module><module>service-b</module><module>service-a</module></modules></project>

3. common 模块（定义 API 契约）

common/pom.xml

<?xml version="1.0" encoding="UTF-8"?><projectxmlns="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>microservice-demo</artifactId><groupId>com.demo</groupId><version>1.0.0</version></parent><modelVersion>4.0.0</modelVersion><artifactId>common</artifactId><dependencies><!-- 必备：包含 @FeignClient 注解 --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><!-- 必备：包含 @GetMapping, @PathVariable 等注解 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- 为了少写 getter/setter，引入 Lombok（可选） --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency></dependencies></project>

common/src/main/java/com/demo/common/dto/User.java

packagecom.demo.common.dto;importlombok.Data;@Data// 自动生成 getter/setter/toStringpublicclassUser{privateLongid;privateStringname;privateStringemail;}

common/src/main/java/com/demo/common/api/UserApi.java

packagecom.demo.common.api;importcom.demo.common.dto.User;importorg.springframework.cloud.openfeign.FeignClient;importorg.springframework.web.bind.annotation.GetMapping;importorg.springframework.web.bind.annotation.PathVariable;// name = "service-b" 对应 B 服务的 spring.application.name// path = "/api" 统一前缀，方便 B 服务统一管理// 这里暂时写死 url，方便不接注册中心直接运行（接入注册中心时删掉 url 即可）@FeignClient(name="service-b",url="http://localhost:8081",path="/api")publicinterfaceUserApi{@GetMapping("/users/{id}")UsergetUserById(@PathVariable("id")Longid);}

4. service-b 模块（服务提供方，实现接口）

service-b/pom.xml

<?xml version="1.0" encoding="UTF-8"?><projectxmlns="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>microservice-demo</artifactId><groupId>com.demo</groupId><version>1.0.0</version></parent><modelVersion>4.0.0</modelVersion><artifactId>service-b</artifactId><dependencies><!-- 依赖 common 模块 --><dependency><groupId>com.demo</groupId><artifactId>common</artifactId><version>1.0.0</version></dependency><!-- web 容器 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency></dependencies></project>

service-b/src/main/resources/application.yml

server:port:8081spring:application:name:service-b# 必须和 @FeignClient(name = "service-b") 保持一致

service-b/src/main/java/com/demo/serviceb/ServiceBApplication.java

packagecom.demo.serviceb;importorg.springframework.boot.SpringApplication;importorg.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication// 重点注意：B 服务是提供方，这里绝对不能加 @EnableFeignClientspublicclassServiceBApplication{publicstaticvoidmain(String[]args){SpringApplication.run(ServiceBApplication.class,args);}}

service-b/src/main/java/com/demo/serviceb/controller/UserController.java

packagecom.demo.serviceb.controller;importcom.demo.common.api.UserApi;importcom.demo.common.dto.User;importorg.springframework.web.bind.annotation.RestController;@RestController// 关键点：实现 common 中定义的接口，自动继承 @GetMapping 路径publicclassUserControllerimplementsUserApi{@OverridepublicUsergetUserById(Longid){// 模拟数据库查询，返回假数据Useruser=newUser();user.setId(id);user.setName("张三（来自B服务）");user.setEmail("zhangsan@service-b.com");returnuser;}}

5. service-a 模块（服务调用方，使用 Feign）

service-a/pom.xml

<?xml version="1.0" encoding="UTF-8"?><projectxmlns="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>microservice-demo</artifactId><groupId>com.demo</groupId><version>1.0.0</version></parent><modelVersion>4.0.0</modelVersion><artifactId>service-a</artifactId><dependencies><!-- 依赖 common 模块 --><dependency><groupId>com.demo</groupId><artifactId>common</artifactId><version>1.0.0</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency></dependencies></project>

service-a/src/main/resources/application.yml

server:port:8080spring:application:name:service-a

service-a/src/main/java/com/demo/servicea/ServiceAApplication.java

packagecom.demo.servicea;importorg.springframework.boot.SpringApplication;importorg.springframework.boot.autoconfigure.SpringBootApplication;importorg.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication// 必须加此注解，并指定扫描 common 模块中 Feign 接口所在的包@EnableFeignClients(basePackages="com.demo.common.api")publicclassServiceAApplication{publicstaticvoidmain(String[]args){SpringApplication.run(ServiceAApplication.class,args);}}

service-a/src/main/java/com/demo/servicea/controller/OrderController.java

packagecom.demo.servicea.controller;importcom.demo.common.api.UserApi;importcom.demo.common.dto.User;importorg.springframework.beans.factory.annotation.Autowired;importorg.springframework.web.bind.annotation.GetMapping;importorg.springframework.web.bind.annotation.PathVariable;importorg.springframework.web.bind.annotation.RestController;@RestControllerpublicclassOrderController{@AutowiredprivateUserApiuserApi;// 直接注入 common 里的接口@GetMapping("/order/{id}/user")publicUsergetOrderUser(@PathVariable("id")Longid){// 看上去像本地调用，实际上发起了 HTTP 请求给 service-breturnuserApi.getUserById(id);}}

6. 运行测试

1. 先启动 service-b（右键运行ServiceBApplication.main），控制台看到Started ServiceBApplication on port 8081。
2. 再启动 service-a（右键运行ServiceAApplication.main），控制台看到Started ServiceAApplication on port 8080。
3. 打开浏览器或 Postman，访问：http://localhost:8080/order/123/user

返回结果（JSON）：

{"id":123,"name":"张三（来自B服务）","email":"zhangsan@service-b.com"}

7. 特别提示（再强调一遍）