創建服務消費者（Feign）

創建服務消費者（Feign）

 

概述

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，只需要創建一個接口並註解。它具有可插拔的註解特性，可使用 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

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

創建服務消費者

創建一個工程名爲 hello-spring-cloud-web-admin-feign 的服務消費者項目，pom.xml 配置如下：

<?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>com.funtl</groupId>
        <artifactId>hello-spring-cloud-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../hello-spring-cloud-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>hello-spring-cloud-web-admin-feign</artifactId>
    <packaging>jar</packaging>

    <name>hello-spring-cloud-web-admin-feign</name>
    <url>http://www.funtl.com</url>
    <inceptionYear>2018-Now</inceptionYear>

    <dependencies>
        <!-- Spring Boot Begin -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Spring Boot End -->

        <!-- Spring Cloud Begin -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!-- Spring Cloud End -->

        <!-- 解決 thymeleaf 模板引擎一定要執行嚴格的 html5 格式校驗問題 -->
        <dependency>
            <groupId>net.sourceforge.nekohtml</groupId>
            <artifactId>nekohtml</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.funtl.hello.spring.cloud.web.admin.feign.WebAdminFeignApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

主要是增加了 Feign 的依賴

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

Application

通過 @EnableFeignClients 註解開啓 Feign 功能

package com.funtl.hello.spring.cloud.web.admin.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
@EnableDiscoveryClient
@EnableFeignClients
public class WebAdminFeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(WebAdminFeignApplication.class, args);
    }
}

application.yml

設置程序端口號爲：8765

spring:
  application:
    name: hello-spring-cloud-web-admin-feign
  thymeleaf:
    cache: false
    mode: LEGACYHTML5
    encoding: UTF-8
    servlet:
      content-type: text/html

server:
  port: 8765

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

創建 Feign 接口

通過 @FeignClient("服務名") 註解來指定調用哪個服務。代碼如下：

package com.funtl.hello.spring.cloud.web.admin.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 = "hello-spring-cloud-service-admin")
public interface AdminService {

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam(value = "message") String message);
}

創建測試用的 Controller

package com.funtl.hello.spring.cloud.web.admin.feign.controller;

import com.funtl.hello.spring.cloud.web.admin.feign.service.AdminService;
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 AdminController {

    @Autowired
    private AdminService adminService;

    @RequestMapping(value = "hi", method = RequestMethod.GET)
    public String sayHi(@RequestParam String message) {
        return adminService.sayHi(message);
    }
}

測試訪問

在瀏覽器上多次訪問 http://localhost:8765/hi?message=HelloFeign

瀏覽器交替顯示：

Hi，your message is :"HelloFeign" i am from port：8762
Hi，your message is :"HelloFeign" i am from port：8763

請求成功則表示我們已經成功實現了 Feign 功能來訪問不同端口的實例