[microservices openfeign] openfeign quick start service invocation based on feign

OpenFeign

OpenFeign It provides a solution for the call between services under the microservice architecture ,OpenFeign It's declarative 、 templated HTTP client .

stay Spring Cloud Use in OpenFeign, It can be used HTTP Request access to remote services , It's like calling a local method , Developers are totally unaware that this is a call to a remote method , More imperceptible in the visit HTTP request .

OpenFeign Can be used to simplify HTTP Call to , We used RestTemplate Realization REST API call , The code looks like this ：

@GetMapping("/buy/{id}")
public Product order() {
    
    Product product = restTemplate.getForObject("http://shop-serviceproduct/product/1", Product.class);
    return product; }

From the code , We use concatenated strings to construct URL Of , The URL There is only one parameter . however , In reality ,URL It often contains multiple parameters . At this time, if we still construct in this way URL, Then it will be very painful .

feign Matters to be called by the client ：

1. If the request parameter is not annotated , By default post Request to send .
2. The service name cannot be underlined , Only middle dash can be used , Otherwise, the following errors will be reported .

feign and opoenfeign

1. They are all built-in at the bottom Ribbon, To call the registry service .
2. Feign yes Netflix Written by the company , yes SpringCloud One of the lightweight components RESTful Of HTTP Service client , yes SpringCloud The first generation load balancing client in .
3. OpenFeign yes SpringCloud Self developed , stay Feign Based on the support of Spring MVC Annotations , Such as @RequesMapping wait . yes SpringCloud Second generation load balancing client in .
4. Feign Itself does not support Spring MVC Annotations , Use Feign The annotation defines the interface , Call this interface , You can call the service in the service registry .
5. OpenFeign Of @FeignClient Can be parsed SpringMVC Of @RequestMapping Interface under annotation , And through the way of dynamic proxy to produce the implementation class , Load balancing in the implementation class and calling other services .

Feign yes Springcloud One of the lightweight components Restful Of HTTP Service client ,Feign Built in Ribbon, It is used for client load balancing , To call the service in the service registry .Feign Is used in the following way ： Use Feign The annotation defines the interface , Call this interface , You can call the service in the service registry .

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

OpenFeign yes springcloud stay Feign Based on the support of SpringMVC Annotations , Such as @RequestMapping wait .OpenFeign Of @FeignClient Can be parsed SpringMVC Of @RequestMapping Interface under annotation , And through the way of dynamic proxy to produce the implementation class , Load balancing in the implementation class and calling other services .

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

be based on Feign Service call for

Introduce dependencies

In serving consumers shop_service_order add to Fegin rely on

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

Startup class add Feign Support for

/** *  consumer  * * @author issavior */
@EnableFeignClients("com.ossa.common.feignapi")
@EnableDiscoveryClient
@SpringBootApplication(scanBasePackages = "com.ossa")
public class ConsumerApplication {
    
    public static void main(String[] args) {
    
        SpringApplication.run(ConsumerApplication.class, args);
    }
}

adopt @EnableFeignClients Annotations to open Spring Cloud Feign Support functions of

Start class activation FeignClient

Create a Feign Interface , This interface is in Feign The core interface for invoking microservices in

In serving consumers shop_service_order Add one ProductFeginClient Interface

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;

/** * @author issavior */
@FeignClient(value = "ossa-service-producer")
@RequestMapping(value = "/producer")
public interface ProducerFeign {
    

    /** *  according to ID Query products  * * @param id  The primary key of the item ID * @return  Information about related products  */
    @GetMapping(value = "/{id}")
    String producerById(@PathVariable(value = "id") String id);

}

• When defining the binding of each parameter ,@PathVariable、@RequestParam、@RequestHeader Parameter properties can be specified , stay Feign The binding parameter in must pass value Property to specify the specific parameter name , Otherwise, an exception will be thrown
• @FeignClient： Comments by name Specify the name of the micro service to be called , Used to create Ribbon Load balancer for .
  therefore Ribbon Will be able to ossa-service-producer Service resolved to registry .

Configure the calling interface of the request provider

modify OrderController , add to ProductFeginClient Automatic injection , And in order Method used in ProductFeginClient Complete the microservice call .

@Autowired
private ProducerFeign producerFeign;

@GetMapping("/feign/{id}")
public String feignConsumerById(@PathVariable(value = "id") String id) {
    

    return producerFeign.producerById(id);
}