Feign project construction

1、Feign

OpenFeign yes Netflix Developed declarative 、 templated HTTP Requesting client , It can be more convenient 、 Call... Gracefully http api.OpenFeign The template of network request will be constructed according to the annotated function information , Before sending a network request ,OpenFeign The parameter values of the function will be set in these request templates .Feign It is mainly to build the consumer end of micro services , Just use OpenFeign The annotation provided modifies the interface class that defines the network request , You can use an instance of this interface to send RESTful Network request for , It can also integrate Ribbon and Hystrix, Provide load balancing and circuit breaker . It's a Http Lightweight framework for request invocation , It can be used Java Interface annotation method call Http request , Not like Java Through encapsulation HTTP The way of request message is called directly , By processing annotations , Template the request , When actually called , Pass in the parameter , Apply to the request again according to the parameters , And turn it into a real request , This kind of request is relatively intuitive .

2、Feign and OpenFeign The relationship between

Feign Itself does not support Spring MVC Annotations , It has its own set of notes .

OpenFeign yes Spring Cloud stay Feign Based on the support of Spring MVC 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 .

3、 Project structures,

（1） Create project User-Provider

Selective dependency ：Spring web、Eureka Discovery Client

（2） Create project User-API

Selective dependency ：spring-boot-starter-web

Create an interface RegisterApi

@RequestMapping("/User")
public interface RegisterApi {

	@GetMapping("/isAlive")
	public String isAlive();
}

（3）User-Provider Realization API

The configuration file

eureka.client.service-url.defaultZone=http://euk1.com:7001/eureka/

server.port=81

spring.application.name=user-provider

introduce API

• maven install User-Api project
• User-Provider Of Pom.xml Add dependency

<dependency>
	 <groupId>com.example.User-API</groupId>
	 <artifactId>User-API</artifactId>
	 <version>0.0.1-SNAPSHOT</version>
</dependency>

establish UserController, And implement Api The interface of  

@RestController
public class UserController implements RegisterApi {

	@Override
	public String isAlive() {
		return "ok";
	}

}

（4）Consumer call

Create project User-Consumer

Selective dependency ：Spring web、Eureka Discovery Client、OpenFeign

introduce API： stay Pom.xml Add dependency

<dependency>
		<groupId>com.example.User-API</groupId>
		<artifactId>User-API</artifactId>
		<version>0.0.1-SNAPSHOT</version>
</dependency>

The configuration file ：

eureka.client.service-url.defaultZone=http://euk1.com:7001/eureka/

server.port=90

spring.application.name=consumer

establish Service Interface

@FeignClient(name = "user-provider")
public interface UserConsumerService extends RegisterApi {

}

establish Controller

@RestController
public class ConsumerController {

	@Autowired
	UserConsumerService consumerSrv;
	
	@GetMapping("/alive")
	public String alive() {
		return consumerSrv.isAlive();
	}
	
}

  Modify the startup class

@SpringBootApplication
@EnableFeignClients
public class UserConsumerApplication {

	public static void main(String[] args) {
		SpringApplication.run(UserConsumerApplication.class, args);
	}

}

（5） test

visit http://localhost:90/alive You can complete the declarative remote service invocation