OpenFeign realize load balance

Official Documentation: SpringCloud OpenFeign

Feign, like RestTemplate, is also an HTTP client request tool, but it is more convenient to use.The first is dependencies:

org.springframework.cloudspring-cloud-starter-openfeign

Then add the @EnableFeignClients annotation to the startup class:

@[email protected] class BorrowApplication {public static void main(String[] args) {SpringApplication.run(BorrowApplication.class, args);}}

So now we need to call the interfaces provided by other microservices, what should we do?We can directly create an interface class corresponding to the service:

@FeignClient("userservice") //The HTTP request client declared as userservice servicepublic interface UserClient {}

Then we directly create the method of the desired type, such as our previous:

RestTemplate template = new RestTemplate();User user = template.getForObject("http://userservice/user/"+uid, User.class);

It can now be written directly like this:

@FeignClient("userservice")public interface UserClient {//The path is guaranteed to be consistent with that provided by other [email protected]("/user/{uid}")User getUserById(@PathVariable("uid") int uid); //The parameter and return value are also consistent}

Then we inject it directly (it smells like Mybatis):

@ResourceUserClient userClient;@Overridepublic UserBorrowDetail getUserBorrowDetailByUid(int uid) {List borrow = mapper.getBorrowsByUid(uid);User user = userClient.getUserById(uid);//There is no need to write IP here, just write the service name bookservice directlyList bookList = borrow.stream().map(b -> template.getForObject("http://bookservice/book/"+b.getBid(), Book.class)).collect(Collectors.toList());return new UserBorrowDetail(user, bookList);}

Access, you can see that the result is still correct:

And we can observe the invocation of the two user microservices, also in the form of load balancing.

According to the same method, we then change the call of the book management service to the interface form:

Finally, our Service code becomes:

@Servicepublic class BorrowServiceImpl implements BorrowService {@ResourceBorrowMapper mapper;@ResourceUserClient userClient;@ResourceBookClient bookClient;@Overridepublic UserBorrowDetail getUserBorrowDetailByUid(int uid) {List borrow = mapper.getBorrowsByUid(uid);User user = userClient.getUserById(uid);List bookList = borrow.stream().map(b -> bookClient.getBookById(b.getBid())).collect(Collectors.toList());return new UserBorrowDetail(user, bookList);}}

Continue to visit for testing:

OK, normal.

Of course, Feign also has many other configuration options, which will not be introduced here, please refer to the official documentation for details.