SpringCloud使用Feign实现远程调用流程详细介绍

<!-- Feign远程调用客户端 -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

@MapperScan("cn.itcast.order.mapper")
@SpringBootApplication
@EnableFeignClients
@Slf4j
public class OrderApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
        log.info("订单微服务启动成功");
    }
}

@FeignClient("userservice")
public interface UserClient {
    @GetMapping("/user/{id}")
    User getById(@PathVariable Long id);
}

@Service
public class OrderService {
    @Autowired
    private OrderMapper orderMapper;
    // 自动注入RestTemplate，用于发起HTTP请求远程调用
    @Autowired
    private RestTemplate restTemplate;
    public Order queryOrderById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
        // 2.使用RestTemplate发起HTTP请求，查询订单所属用户信息
        // 2.1 根据查询的订单order中的userId动态生成HTTP请求的url
        String url = "http://userservice/user/" + order.getUserId();
        // 2.2 发送HTTP请求，实现远程调用
        User user = restTemplate.getForObject(url, User.class);
        // 3.把远程调用获得的user封装进order对象中
        order.setUser(user);
        // 4.返回order订单信息
        return order;
    }
}

@Service
public class OrderService {
    @Autowired
    private OrderMapper orderMapper;
    // 自动注入userservice的Feign客户端，用于发起HTTP请求远程调用
    @Autowired
    private UserClient userClient;
    public Order queryOrderById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
        // 2.使用Feign客户端发起HTTP请求，查询订单所属用户信息
        User user = userClient.getById(order.getUserId());
        // 3.把远程调用获得的user封装进order对象中
        order.setUser(user);
        // 4.返回order订单信息
        return order;
    }
}