Spring Cloud OpenFeign + Nacos 实战教程：像调用本地方法一样调用远程微服务

RestTemplate restTemplate = new RestTemplate();
UserDTO user = restTemplate.getForObject("http://user-service/users/1", UserDTO.class);

UserDTO user = userClient.getUserById(1L);

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>

    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
</dependencies>

feign-demo/
├── user-service/
│   ├── UserApplication.java
│   ├── controller/UserController.java
│   └── model/UserDTO.java
│
└── order-service/
    ├── OrderApplication.java
    ├── controller/OrderController.java
    ├── client/UserClient.java
    ├── client/UserClientFallback.java
    └── model/UserDTO.java

sh nacos/bin/startup.sh -m standalone

server:
  port: 8081
spring:
  application:
    name: user-service
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848

server:
  port: 8082
spring:
  application:
    name: order-service
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848

feign:
  client:
    config:
      default:
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: full
  circuitbreaker:
    enabled: true

logging:
  level:
    com.example.order.client: DEBUG

@SpringBootApplication
@EnableDiscoveryClient
public class UserApplication {
    public static void main(String[] args) {
        SpringApplication.run(UserApplication.class, args);
    }
}

@RestController
@RequestMapping("/users")
public class UserController {

    @GetMapping("/{id}")
    public UserDTO getUserById(@PathVariable Long id) {
        return new UserDTO(id, "张三-" + id);
    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public class UserDTO {
    private Long id;
    private String name;
}

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
}

@FeignClient(name = "user-service", fallback = UserClientFallback.class)
public interface UserClient {

    @GetMapping("/users/{id}")
    UserDTO getUserById(@PathVariable("id") Long id);
}

@Component
public class UserClientFallback implements UserClient {

    @Override
    public UserDTO getUserById(Long id) {
        return new UserDTO(id, "（熔断：无法获取用户信息）");
    }
}

@RestController
@RequiredArgsConstructor
@RequestMapping("/orders")
public class OrderController {

    private final UserClient userClient;

    @GetMapping("/{userId}")
    public String createOrder(@PathVariable Long userId) {
        UserDTO user = userClient.getUserById(userId);
        return "订单已创建，用户：" + user.getName();
    }
}

sh nacos/bin/startup.sh -m standalone

GET http://localhost:8082/orders/1

订单已创建，用户：张三-1

订单已创建，用户：（熔断：无法获取用户信息）