OpenFeign实现服务发现远程调用以及负载均衡-SpringCloudAlibaba No.2

Posted 2022-05-06 Fire king

OpenFeign实现服务发现远程调用以及负载均衡

• • 1.导入依赖
  • 2.编写接口（@FeignClient和@EnableFeignClients）：
  • • 2.1.借阅类
    • 2.2.图书类和用户类
  • 3.可能出现的bug

1.导入依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<!-- 这里需要单独导入LoadBalancer依赖 -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

2.编写接口（@FeignClient和@EnableFeignClients）：

2.1.借阅类

注意：@FeignClient的值userservice和bookservice需要在对应服务的配置文件配置服务名称且一一对应，我们在nacos那一篇已经配置过了：传送门。

@FeignClient("userservice")
public interface UserClient 

    @RequestMapping("/user/uid")
    User getUserById(@PathVariable("uid") int uid);

@FeignClient("bookservice")
public interface BookClient 

    @RequestMapping("/book/bid")
    Book getBookById(@PathVariable("bid") int bid);

@Service
public class BorrowServiceImpl implements BorrowService

    @Resource
    BorrowMapper mapper;

    @Resource
    UserClient userClient;

    @Resource
    BookClient bookClient;

    @Override
    public UserBorrowDetail getUserBorrowDetailByUid(int uid) 
        List<Borrow> borrow = mapper.getBorrowsByUid(uid);
        User user = userClient.getUserById(uid);
        List<Book> bookList = borrow
                .stream()
                .map(b -> bookClient.getBookById(b.getBid()))
                .collect(Collectors.toList());
        return new UserBorrowDetail(user, bookList);
    

注意：加@EnableFeignClients才能是配置生效

@EnableFeignClients
@SpringBootApplication
public class BorrowApplication 
    public static void main(String[] args) 
        SpringApplication.run(BorrowApplication.class, args);
    

2.2.图书类和用户类

图书类：

@RestController
public class BookController 

    @Resource
    BookService service;

    @RequestMapping("/book/bid")
    Book findBookById(@PathVariable("bid") int bid,
                      HttpServletRequest request)
        System.out.println(request.getHeader("Test"));
        return service.getBookById(bid);
    

用户类：

@RestController
public class UserController 

    @Resource
    UserService service;

    @RequestMapping("/user/uid")
    public User findUserById(@PathVariable("uid") int uid)
        System.out.println("我被调用拉！");
        return service.getUserById(uid);
    

3.可能出现的bug

如果出现RestTemplate字眼的bug，需要注册RestTemplate的bean。