[Java知识库]声明式服务调用 Feign get请求传递参数

1. 进入到nacos安装目录，Linux开启 nacos 服务
   nacos安装

docker-compose -f example/standalone-derby.yaml up

2. 创建Spring Cloud 工程
   

• 添加依赖注意版本号

- 父

pom.xml

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.12.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>2.2.7.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Hoxton.SR12</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>31.1-jre</version>
        </dependency>
    </dependencies>

provider

1. pom.xml 导入注册discovery 、连接数据库 和 mybatis-plus 的必要依赖

<dependencies>
        <!--        注册中心依赖-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.8</version>
        </dependency>
    </dependencies>

2. application.yml 配置nacos:discovery 相关属性 服务器地址和nacos命名空间

server:
  port: 8880
  servlet:
    context-path: "/api/"

spring:
  profiles:
    active: dev
  application:
    # 服务器名
    name: provider-server
  cloud:
    nacos:
      discovery:
        #  配置服务的名称 默认值 spring.application.name
        #        service:
        # 配置注册中心的地址  如果是集群 使用,隔开
        server-addr: "192.168.140.130:8848"
        # 配置注册中心的命名空间  隔离环境的作用
        # 注意 所有的应用必须注册在同一个命名空间下  默认是public
        namespace: "b091994d-1518-4537-9ad6-290c821dd681"
        # 如果注册中开启了 用户认证
        username: ""
        password: ""

3. 配置 mybatis-plus
   

@Configuration
@MapperScan("com.smart.provider.**.mapper")
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
        PaginationInnerInterceptor paginationInnerInterceptor = new PaginationInnerInterceptor();
        paginationInnerInterceptor.setOverflow(true);
        paginationInnerInterceptor.setMaxLimit(50L);
        mybatisPlusInterceptor.addInnerInterceptor(paginationInnerInterceptor);
        return mybatisPlusInterceptor;
    }
}

5. 反向生成数据库 user 表（entity、mapper、mapper.xml ）
6. service

@Service
public class UserService {

    @Resource
    UserMapper userMapper;
    public List<User> userList(int page,int size){
        Page<User> selectPage = userMapper.selectPage(new Page<>(page, size), new QueryWrapper<>());
        return selectPage.getRecords();
    }
}

7. controller

@RestController
@RequestMapping("/provider")
public class ProviderController {
    @Resource
    UserService userService;

    @GetMapping("/hello")
    public String hello() {
        return "provider";
    }

    @GetMapping("/user")
    public List<User> userList(int page,int size) {
        return userService.userList(page,size);
    }
}

consumer

1. pom.xml 引入nacos、feign相关依赖

    <dependencies>
        <!--        注册中心依赖-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery
            </artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>

2. application.yml

server:
  port: 8881
spring:
  application:
    # 服务器名
    name: consumer-server
  cloud:
    nacos:
      discovery:
        server-addr: "192.168.140.130:8848"
        namespace: "b091994d-1518-4537-9ad6-290c821dd681"

3. 启动类 @EnableFeignClients 将feignClient接口注入到spring ioc

@SpringBootApplication
//将feignClient接口注入到spring ioc
@EnableFeignClients
public class ConsumerApp {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerApp.class, args);
    }
}

4. user实体类也要写在consumer，删掉不必要的注解
5. 服务降级

/**
 * 服务降级
 */
@FeignClient(name = "provider-server", path = "/api/provider")
public interface ProviderApi {
    @GetMapping("/user")
    List<User> userList(@RequestParam int page, @RequestParam int size);
}

6. controller

@RestController
public class ConsumerController {
    @Resource
    ProviderApi providerApi;
    @GetMapping("/user")
    public List<User> userList(int page,int size) {
        return providerApi.userList(page, size);
    }
}

7. provider 开启多实例运行 修改端口号 8880、8882两个实例
   
   

测试

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