SpringBoot2 整合 SpringCloud Feign 实例

1. 简介

Feign 是一个声明式的伪Http客户端，使用时只需要创建一个接口并注解。
Feign 默认集成了 Ribbon，并和 Eureka 结合，默认实现了负载均衡的效果。

2. 工程实例

在这篇文章： SpringBoot2 整合 SpringCloud Ribbon 实现负载均衡实例 中我们使用RestTemplate+Ribbon去消费服务，本篇文章主要讲述如何通过Feign去消费服务。

工程目录如下图所示：

root 工程 spring-study，root 工程的 pom.xml 如下所示：

<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>4.0.0modelVersion>

    <groupId>com.syrdbtgroupId>
    <artifactId>studyartifactId>
    <packaging>pompackaging>
    <version>1.0-SNAPSHOTversion>
    <modules>
        <module>springcloud-study-eureka-servermodule>
        <module>springcloud-study-feignmodule>
        <module>springcloud-study-hello-servicemodule>
    modules>

    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.7.RELEASEversion>
        <relativePath/>
    parent>

    <properties>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8project.reporting.outputEncoding>
        <java.version>1.8java.version>
        <spring-cloud.version>Finchley.RELEASEspring-cloud.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloudgroupId>
                <artifactId>spring-cloud-dependenciesartifactId>
                <version>${spring-cloud.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>

2.1 注册中心 springcloud-study-eureka-server

工程目录如下所示：

2.1.1 依赖 pom.xml

pom.xml 的依赖如下所示：

<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>studyartifactId>
        <groupId>com.syrdbtgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>

    <modelVersion>4.0.0modelVersion>

    <artifactId>eurkea-serverartifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-serverartifactId>
        dependency>
    dependencies>
project>

2.1.2 配置文件 application.properties

配置文件如下所示：

# 服务注册中心端口号
server.port=8761
# 服务注册中心主机名
eureka.instance.hostname=127.0.0.1
# 不向注册中心注册自己
eureka.client.register-with-eureka=false
# 不需要检索服务
eureka.client.fetch-registry=false
# 注册中心地址，会自动填充 主机名 和 端口号
eureka.client.service-url.defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

2.1.3 启动类 EurekaServerApplication.java

package com.syrdbt.study.eureka.server;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

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

}

2.2 服务提供者 springcloud-study-hello-service

工程目录如下所示：

2.2.1 依赖 pom.xml

pom.xml 如下所示：

<?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>study</artifactId>
        <groupId>com.syrdbt</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>hello-service</artifactId>

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

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2.2.2 配置文件 application.yml

eureka:
  client:
    serviceUrl:
      #注册中心的地址
      defaultZone: http://localhost:8761/eureka/
server:
  #当前服务端口号
  port: 8762
spring:
  application:
    #当前应用名称,当前应用的名称
    name: service-hi

2.2.3 控制器 HelloController.java

package com.syrdbt.study.hello.service.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@RestController
public class HelloController {
    @Value("${server.port}")
    private String port;

    @RequestMapping(value = "hello", method = RequestMethod.GET)
    public String index() {
        return "eurekaClient：Hello World " + this.port;
    }
}

2.2.4 启动类 HelloServiceApplication.java

package com.syrdbt.study.hello.service;

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

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@SpringBootApplication
@EnableEurekaClient
public class HelloServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(HelloServiceApplication.class, args);
    }
}

2.3 springcloud-study-feign

2.3.1 依赖 pom.xml

<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>studyartifactId>
        <groupId>com.syrdbtgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>

    <artifactId>feignartifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>
    dependencies>
project>

2.3.2 配置文件 application.yml

application.yml：

server:
  port: 8765
spring:
  application:
    # 该服务的名字
    name: server-feign
eureka:
  client:
    serviceUrl:
      # eureka服务的地址
      defaultZone: http://localhost:8761/eureka/

2.3.3 Fegin 接口 HelloFeign

通过@ FeignClient（“服务名”），来指定调用哪个服务。下面的示例中调用了service-hi服务的“/hello”接口，HelloFeign.java 代码如下：

package com.syrdbt.study.feign;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@FeignClient(name = "service-hi")
public interface HelloFeign {

    @RequestMapping(value="/hello")
    String hello();
}

2.3.4 调用 feign 接口的控制器

HelloController.java，通过上面定义的Feign客户端 HelloFeign 来消费服务。

package com.syrdbt.study.feign.controller;

import com.syrdbt.study.feign.HelloFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@RestController
public class HelloController {
    @Autowired
    private HelloFeign helloFeign;

    @GetMapping(value="/hello")
    public String getHi() {
        return helloFeign.hello();
    }
}

2.3.5 启动类 FeignApplication

package com.syrdbt.study.feign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

/**
 * @author syrdbt
 * @date 2019-10-12
 */
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
@EnableDiscoveryClient
public class FeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(FeignApplication.class, args);
    }
}

3. 启动并测试

需要启动4个实例。
⚠️注意：HelloServiceApplication 需要启动两个，两个的端口号分别为 8762 和 8763 。
IDEA 启动多实例教程：https://www.cnblogs.com/wuxun1997/p/11208519.html。

3.1 注册中心的情况

访问 http://localhost:8761/ 。
注册中心注册的 实例如下所示：

3.2 测试访问

访问：http://localhost:8765/hello 。
运行截图如下所示：

参考文献

• SpringCloud 微服务实战 - 作者 ：崔永超老师
• https://www.fangzhipeng.com/springcloud/2018/08/03/sc-f3-feign.html