Original address :Spring Cloud introduction And Feign piece ( 3、 ... and )

Blog address :http://www.extlight.com

One 、 Preface

In the last article 《Spring Cloud introduction And Ribbon piece ( Two )》 This paper introduces the in Ribbon Using load balancing to call microservices , But there is a problem : Each request method of the consumer needs to splice the URL Address , There are hard coding problems and it does not conform to the idea of object-oriented programming . If the service name changes , The consumer side also needs to be modified .

This article will introduce Feign To solve the problems above .

Two 、 Brief introduction

Feign It's a declarative one Web Service client . Use Feign Can make writing Web Service The client is simpler , Support and at the same time Eureka、Ribbon Combined to support load balancing .

Spring Cloud Yes Feign It was packaged , To support Spring MVC Standard notes and HttpMessageConverters.

Feign The way to use it is to define an interface , Then add... To it @FeignClient annotation .

3、 ... and 、 Practical drill

This test case is based on the case described in the previous published article , If you are not sure, please move to 《Spring Cloud introduction And Ribbon piece ( Two )》 Browse .

3.1 Add dependency

stay common-api and order-server Add dependency in project :

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

3.2 Define a new interface

stay common-api Create a new interface in the project :

@FeignClient(value="GOODS")
public interface GoodsServiceClient { @RequestMapping("/goods/goodsInfo/{goodsId}")
public Result goodsInfo(@PathVariable("goodsId") String goodsId);
}

Use @FeignClient The annotation specifies the name of the microservice to be called , Encapsulates the call USER-API The process of , Call template as consumer .

Be careful :Feign The definition of interface is best related to that of external development controller The method definitions in are consistent , The definition here is similar to goods-server In the project controller The method of class definition is consistent .

3.3 Modify call

stay order-server In the project , Use GoodsServiceClient Access to product information :

@Service
public class OrderServiceImpl implements OrderService{ // @Autowired
// private RestTemplate restTemplate; @Autowired
private GoodsServiceClient goodsServiceClient; @Override
public void placeOrder(Order order) throws Exception{ //Result result = this.restTemplate.getForObject("http://GOODS/goods/goodsInfo/" + order.getGoodsId(), Result.class); Result result = this.goodsServiceClient.goodsInfo(order.getGoodsId()); if (result != null && result.getCode() == 200) {
System.out.println("===== Place the order ====");
System.out.println(result.getData());
}
} }

Use it directly Feign Encapsulating the template calls the server , Free from trouble URL Splicing problem , So as to realize object-oriented programming .

3.4 start-up Feign function

Add on the startup class @EnableEeignClients annotation :

@EnableFeignClients(basePackages = {"com.extlight.springcloud"})
@EnableEurekaClient
@SpringBootApplication
public class OrderServerApplication { public static void main(String[] args) {
SpringApplication.run(OrderServerApplication.class, args);
}
}

because order-server The project quoted common-api Medium GoodsServiceClient, It's different from a project , To instantiate objects , So you need to @EnableFeignClients Add the package path to be scanned in the annotation .

Use Postman Request order system , The result of the request is as follows :

The request is successful , because Feign Encapsulates the Ribbon, It also realizes the function of load balancing .

Four 、 Source code of case

Feign demo Source code

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