一. Feigin簡介
Feign是一個聲明式的僞Http用戶端,它使得寫Http用戶端變得更簡單。使用Feign,隻需要建立一個接口并用注解的方式來配置它,即可完成對服務提供方的接口綁定,簡化了在使用Ribbon時自行封裝服務調用用戶端的開發量。
Feign具有可插拔的注解特性,包括Feign 注解和JAX-RS注解,同時也擴充了對SpringMVC的注解支援。Feign支援可插拔的編碼器和解碼器,預設內建了Ribbon,并和Eureka結合,預設實作了負載均衡的效果。
二. 快速入門
2.1 啟動之前的eureka-server工程,端口号為8761,啟動eureka-client工程兩次,端口号為8762和8763。
2.2 建立Feign服務
首先建立一個Spring Boot基礎工程,命名為service-feign,在pom.xml中引入必要的依賴:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.dan</groupId>
<artifactId>service-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>service-feign</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Edgware.SR1</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
在工程的配置檔案application.properties檔案上配置指定服務注冊中心、自身的服務名、端口号等:
spring.application.name=service-feign
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka
server.port=8765
在啟動類上加上@EnableFeignClients注解開啟Feign的支援功能:
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ServiceFeignApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceFeignApplication.class, args);
}
}
定義HelloService接口,通過@FeignClient注解指定服務名來綁定服務指定調用哪個服務,然後再使用Spring MVC的注解來綁定具體該服務提供的REST接口:
@FeignClient("hello-service")
public interface HelloService {
@GetMapping("/hello")
String hello(@RequestParam(value = "name") String name);
}
接着,建立一個controller來實作對Feign用戶端的調用
@RestController
public class HelloController {
@Autowired
HelloService helloService;
@GetMapping(value = "/hello")
public String sayHi(@RequestParam(value = "name") String name){
return helloService.sayHello(name);
}
}
啟動工程,Eureka Server的資訊面闆:
多次通路localhost:8765/hello?name=Jack 交替看到:
Hello Jack. I am from port:8762
Hello Jack. I am from port:8763
源碼下載下傳:https://github.com/lingd3/SpringCloudLearning/tree/master/chapter4