(拿來主義) SpringCloud | 第三篇: 服務消費者(Feign)

1、Feign簡介

Feign是一個聲明式的僞Http客戶端,它使得寫Http客戶端變得更簡單。使用Feign,只須要建立一個接口並註解。它具備可插拔的註解特性,可以使用Feign 註解和JAX-RS註解。Feign支持可插拔的編碼器和解碼器。Feign默認集成了Ribbon,並和Eureka結合,默認實現了負載均衡的效果。java

簡而言之:web

  • Feign 採用的是基於接口的註解
  • Feign 整合了ribbon

2、準備工做

繼續用上一節的工程, 啓動eureka-server,端口爲1111; 啓動service-hi 兩次,端口分別爲222二、3333.spring

3、建立一個feign的服務

新建一個spring-boot工程,取名爲serice-feign,在它的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,代碼以下:apache

<?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.example.springcloud</groupId>
    <artifactId>feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>feign</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.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>Finchley.SR1</spring-cloud.version>
    </properties>

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

        <!--  feign相關依賴-->
        <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>

 

在工程的配置文件application.xml文件,指定程序名爲service-feign,端口號爲5555,服務註冊地址爲http://localhost:1111/eureka/ ,代碼以下:瀏覽器

server.port = 5555

spring.application.name = service-feign

eureka.client.serviceUrl.defaultZone = http://localhost:1111/eureka/

 

定義一個feign接口,經過@ FeignClient(「服務名」),來指定調用哪一個服務。好比在代碼中調用了service-hi服務的「/hi」接口,代碼以下:app

package com.example.springcloud.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;

@FeignClient(value = "service-hi")
public interface SchedualServiceHi {
@RequestMapping(value = "/hi",method = RequestMethod.GET)
String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

在Web層的controller層,對外暴露一個」/hi」的API接口,經過上面定義的Feign客戶端SchedualServiceHi 來消費服務。代碼以下負載均衡

package com.example.springcloud.feign.web;

import com.example.springcloud.feign.service.SchedualServiceHi;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HiController {
    @Autowired
    SchedualServiceHi schedualServiceHi;
    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    public String sayHi(@RequestParam String name){
        return schedualServiceHi.sayHiFromClientOne(name);
    }
}

在程序的啓動類ServiceFeignApplication ,加上@EnableFeignClients註解開啓Feign的功能:maven

 

package com.example.springcloud.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;

@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication
public class FeignApplication {

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

 

啓動程序,屢次訪問http://localhost:5555/hi?name=forezp,瀏覽器交替顯示:spring-boot

 

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