宣告性REST客戶端：Feign

對於feign，springCloud官方如是說：

Feign是一個宣告式的Web服務客戶端。這使得Web服務客戶端的寫入更加方便 要使用Feign建立一個介面並對其進行註釋。它具有可插入註釋支援，包括Feign註釋和JAX-RS註釋。Feign還支援可插拔編碼器和解碼器。Spring Cloud增加了對Spring MVC註釋的支援，並使用Spring Web中預設使用的HttpMessageConverters。Spring Cloud整合Ribbon和Eureka以在使用Feign時提供負載均衡的http客戶端。

使用三個測試專案：

先啟動伺服器和提供介面的客戶端：

在eureka可以看到發現了一個微服務，在這個客戶端有一個介面：

好，準備工作做完，開始寫feign:

首先加入依賴

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

<?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">
    <parent>
        <artifactId>SpringCloudTest</artifactId>
        <groupId>com.xc.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>EurekaService_feign</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

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

    </dependencies>

</project>
 

package com.xc;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class App_feign {
    public static void main(String args[]){
        SpringApplication.run(App_feign.class);
    }
}
 

完整如下：

spring:
  application:
    name: test_feign
server:
  port: 7777
eureka:
  client:
    healthcheck:
      enabled: true
    serviceUrl:
      defaultZone: http://xc:[email protected]:8761/eureka
  instance:
    prefer-ip-address: true

package com.xc.feign;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient("cloud-test")
public interface TestFeign {
    @RequestMapping(value = "/say/{words}",method = RequestMethod.GET)
    public String sayHello(@PathVariable("words") String words);
}

然後寫一個rest介面：

package com.xc.controller;

import com.xc.feign.TestFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

         @Autowired
        private TestFeign testFeign;

        @RequestMapping(value="/say/{word}",method = RequestMethod.GET)
        public String say(@PathVariable String word){
            return testFeign.sayHello(word);
        }

}

訪問http://192.9.8.3:7777/say/haha

成功獲取到資料。