Feign 远程调用

OpenFeign官方文档 Feign和RestTemplate一样，也是HTTP客户端请求工具，但是它的使用方式更加便捷。 在需要使用Feign的服务中添加依赖

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

在启动类添加注解 @EnableFeignClients 创建需要的Client

@FeignClient("UserService")   //声明为 UserService 服务的HTTP请求客户端
public interface UserClient {
    //路径保证和微服务提供的一致即可
    @GetMapping("/users/{uid}")
    User getUserById(@PathVariable("uid") int uid);
}

@FeignClient("BookService")
public interface BookClient {
    @GetMapping("/books/{bid}")
    Book getBookById(@PathVariable int bid);
}

修改之前使用Rest Template的服务

@Service
public class BorrowServiceImpl implements BorrowService {
    @Resource
    private BorrowMapper borrowMapper;
    @Resource
    UserClient userClient;
    @Resource
    BookClient bookClient;
    @Override
    public UserBorrowDetail getUserBorrowDetailByUid(int uid) {
        List<Borrow> borrowsByUid = borrowMapper.getBorrowsByUid(uid);
        User user = userClient.getUserById(uid);
        List<Book> bookList = borrowsByUid
            .stream()
            .map(borrow -> bookClient.getBookById(borrow.getBid()))
            .collect(Collectors.toList());
        return new UserBorrowDetail(user,bookList);
    }
}