一、Feign簡介:
Feign是一個聲明式的僞Http客戶端,使得寫Http客戶端變得更簡單。使用Feign,只需要創建一個接口並註解,可使用Feign 註解和JAX-RS註解。Feign默認集成了Ribbon,並和Eureka結合,默認實現了負載均衡的效果。
二、前提:
繼續用上一節的工程, 啓動eureka-server,端口爲8763; 啓動eureka-client-zyy-demo兩次,端口分別爲8762 、8764。
三、創建一個feign的服務
1.新建一個spring-boot工程,取名爲demo_eureka_feign,在pom文件引入Feign的起步依賴spring-cloud-starter-feign、Eureka的起步依賴spring-cloud-starter-eureka、Web的起步依賴spring-boot-starter-web。
<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo_eureka_feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo_eureka_feign</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.SR2</spring-cloud.version>
</properties>
<dependencies>
<!--Eureka的起步依賴-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<!--Feign的起步依賴-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<!--Web的起步依賴-->
<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>
2.在配置文件application.yml中,指定項目名爲service-feign,端口號爲8765,服務註冊地址爲http://localhost:8763/eureka/
3.在項目啓動類DemoEurekaFeignApplication,加上@EnableFeignClients註解開啓Feign功能。
package com.example.demo_eureka_feign;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication //springBoot 啓動標識
@EnableDiscoveryClient //微服務調用
@EnableFeignClients // 微服務調用
/**
* @EnableFeignClients註解開啓Feign的功能
*/
public class DemoEurekaFeignApplication {
public static void main(String[] args) {
SpringApplication.run(DemoEurekaFeignApplication.class, args);
}
}
4.創建一個service層,定義一個feign接口,通過@ FeignClient(“服務名”),來指定調用哪個服務。
比如在代碼中調用了eureka-client-zyy-demo服務的“/hi”接口,代碼如下:
package com.example.demo_eureka_feign.service;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
/**
* 定義一個feign接口,通過@ FeignClient(“服務名”),來指定調用哪個服務。
* 比如在代碼中調用了eureka-client-zyy-demo服務的“/hi”接口.
*/
@FeignClient(value = "eureka-client-zyy-demo")
public interface SchedualServiceHi {
@RequestMapping(value = "/hi",method = RequestMethod.GET)
String sayHiFromClientOne(@RequestParam(value = "name") String name);
}
5.創建一個controller層,對外暴露一個"/hi"的API接口,通過上面定義的Feign客戶端SchedualServiceHi 來消費服務。
package com.example.demo_eureka_feign.controller;
import com.example.demo_eureka_feign.service.SchedualServiceHi;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
/**
* 對外暴露一個"/hi"的API接口,通過上面定義的Feign客戶端SchedualServiceHi 來消費服務
*/
@RestController
public class HiController {
@Autowired
SchedualServiceHi schedualServiceHi;
@GetMapping(value = "/hi")
public String sayHi(@RequestParam String name) {
return schedualServiceHi.sayHiFromClientOne( name );
}
}
6.啓動程序,多次訪問http://localhost:8765/hi?name=forezp,瀏覽器交替顯示:
hi forezp,i am from port:8762
hi forezp,i am from port:8764