• SpringCloud学习成长之路三 服务消费者(Feign)


    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

      使用之前做好的项目文件, 启动eureka-server,端口为8761; 启动service-hi 两次,端口分别为8762 、8763.

    三、创建一个feign的服务

      新建一个spring-boot工程,取名为serice-feign,在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web,代码如下:

    <?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>
    
        <groupId>com.forezp</groupId>
        <artifactId>service-feign</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>service-feign</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.2.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>
        </properties>
    
        <dependencies>
            <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-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>Dalston.RC1</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>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>
    
    
    </project>

      在工程的配置文件application.yml文件,指定程序名为service-feign,端口号为9900,服务注册地址为http://localhost:8761/eureka/ ,代码如下:

    eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8761/eureka/
    server:
      port: 9900
    spring:
      application:
        name: service-feign

      在程序的启动类ServiceFeignApplication ,加上@EnableFeignClients注解开启Feign的功能:

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

      定义一个feign接口,通过@ FeignClient(“服务名”),来制定使用哪个Eureka客户端服务

      接口方法上加上@RequestMapping(value = "/hi",method = RequestMethod.GET)表示调用路径为/hi的方法get方式 传递参数为  String  name

    代码如下:

    /**
     * Created by fangzhipeng on 2017/4/6.
     */
    @FeignClient(value = "service-hi")
    @Service
    public interface SchedualServiceHi { 
      @RequestMapping(value
    = "/hi",method = RequestMethod.GET)
      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:

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

    启动程序,使用postMan工具多次多次访问http://localhost:9900/hi?name=kksks    交替显示调用8762    8763

    hi kksks,i am from port:8762

    hi kksksi am from port:8763

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  • 原文地址:https://www.cnblogs.com/kuoAT/p/9141886.html
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