Feign use

Feign Introduce

Feign It belongs to one of interface calls ,

name	explain
Httpclient	HttpClient yes Apache Jakarta Common Sub projects under , To provide efficient 、 Abreast of the times 、 Feature rich support Http Client programming toolkit for protocol , And it supports HTTP The latest version of the agreement and recommendations .HttpClient Compared with tradition JDK Self contained URLConnection, Improved ease of use and flexibility , Make the client send HTTP It's easier to ask , Improved development efficiency .
Okhttp	An open source project to handle network requests , It's the most popular lightweight framework in Android , from Square The company contributed , Used in substitution HttpUrlConnection and Apache HttpClient.OkHttp Have a simple API、 Efficient performance , And support a variety of protocols （HTTP/2 and SPDY）.
HttpURLConnection	HttpURLConnection yes Java Standard class , It is inherited from URLConnection, Can be used to send GET request 、POST request .HttpURLConnection It's complicated to use , Unlike HttpClient That's easy to use .
RestTemplate	RestTemplate yes Spring Provided for access Rest Client of service ,RestTemplate Provides a variety of convenient remote access HTTP Method of service , Can greatly improve the writing efficiency of the client .
Feign	Feign It's a declarative one REST client , It can make REST It's easier to call .Feign For HTTP Requested template , By writing simple interfaces and inserting annotations , You can define HTTP Requested parameters 、 Format 、 Address and other information . and Feign It'll be a complete agent HTTP request , We only need to call it like a method to complete the service request and related processing .Spring Cloud Yes Feign It was packaged , To support SpringMVC Standard notes and HttpMessageConverters.Feign It can be done with Eureka and Ribbon Combined to support load balancing .

Get ready

start-up Eureka service , And register two applications as test cluster machines , As shown in the figure ; Test interface /hello

Feign Project use

To configure pom.xml rely on

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>

encapsulation Feign Interface ,eureka-provider-app To register to Eureka Service name in

@FeignClient(value = "eureka-provider-app")
public interface TestClient {
    
	@GetMapping("/hello")
	String hello();
}

To configure client scanning

@SpringBootApplication
@EnableFeignClients(basePackageClasses = {
    TestClient.class})
public class Application {
    
	public static void main(String[] args) {
    
		SpringApplication.run(Application.class, args);
	}
}

The configuration file application.properties add to Eureka Registration configuration

eureka.client.serviceUrl.defaultZone=http://192.168.1.55:8761/eureka/

Add test class

@RestController
public class TestController {
    
	@Autowired
	private TestClient client;

	@GetMapping("/test")
	public String test() {
    
		String result = client.hello();
		return result;
	}
}

test , Test success