SpringCloud之服务消费者(Feign)

作者: FinalException | 来源:发表于2020-03-11 00:03 被阅读0次

一、Feign简介

Feign是一个声明式的伪Http客户端，它使得写Http客户端变得更简单。使用Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

简而言之：

Feign 采用的是基于接口的注解
Feign 整合了ribbon

二、准备工作

1.搭建并启动eureka服务

新建springboot项目
名称随意
添加依赖，这里只需eureka server即可
选择项目保存位置，可以按需修改
建好后先在命令行打包检查项目依赖是否有问题

在resource目录下新建配置文件application.yml,内容如下：

server:
  port: 8761
spring:
  application:
    name: eureka-server

eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://127.0.0.1:${server.port}/eureka/

在启动类上添加注解@EnableEurekaServer
启动项目，访问 http://127.0.0.1:8761

至此eureka服务搭建完成。

2.创建一个Feign服务

此处取名为feign-load-balance,对应的pom.xml如下：

需要注意的是pom中的Springboot和SpringCloud之间版本对应关系

可以移步至此查看对应版本：https://start.spring.io/actuator/info

<?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 https://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>1.5.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.feign.load.balance</groupId>
    <artifactId>feign-load-balance</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>feign-load-balance</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Dalston.SR1</spring-cloud.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <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.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</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.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven-compiler-plugin.version}</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>${project.build.sourceEncoding}</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

在配置文件application.yml中指定程序名端口号和eureka注册中心地址

spring:
  application:
    name: feign-load-balance

server:
  port: 9091

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/

在程序启动类上加上相关注解：

定义一个feign接口，通过@ FeignClient（“服务名”），来指定调用哪个服务。比如在代码中调用了service-hi服务的“/hi”接口，代码如下：

/**
 * @Author YanQiQi
 * @Date 2020-03-10 16:33
 **/
@FeignClient(value = "service-hi")
public interface ScheduleServiceHi {

    /**
     * sayHiFromClientOne
     *
     * @param name name
     * @return String
     */
    @GetMapping(value = "/hi")
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

在Web层的controller层，对外暴露一个"/hi"的API接口，通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下：

/**
 * @Author YanQiQi
 * @Date 2020-03-10 16:28
 **/
@RestController
public class HiController {

    @Autowired
    private ScheduleServiceHi scheduleServiceHi;

    @GetMapping("/hi")
    public String sayHello(@RequestParam String name) {
        return scheduleServiceHi.sayHiFromClientOne(name);
    }
}

启动feign-load-balance项目，访问eureka注册中心，可以看到服务注册成功，Feign服务即创建启动完成。

3.创建service-hi（示例服务），使用不同的端口启动，用于测试负载均衡

service-hi服务的搭建与上面类似，对应的pom.xml如下：

同样也需要注意Springboot和SpringCloud版本的对应

<?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 https://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>1.5.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com</groupId>
    <artifactId>service-hi</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>service-hi</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Dalston.SR1</spring-cloud.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <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.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</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.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven-compiler-plugin.version}</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>${project.build.sourceEncoding}</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

在配置文件application.yml中指定程序名端口号和eureka注册中心地址

spring:
  application:
    name: service-hi

server:
  port: 9093
# [9092,9093...]可以多个端口分别启动进行负载均衡
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/

启动类添加相关注解

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class ServiceHiApplication {

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

}

Controller定义Feign服务要调用的接口，此处为/hi

/**
 * @Author YanQiQi
 * @Date 2020-03-10 17:14
 **/
@RestController
public class HiController {

    @Autowired
    private MyConfig myConfig;


    @GetMapping("/hi")
    public String sayHi(@RequestParam String name) {
        return "hi " + name + "your ip.port is " + myConfig.getPort();
    }
}